FINAL REPORT - SAWIS libraryResearcher surname 4 This document is confidential and any unauthorised disclosure is prohibited Version 2015 4. Determine the effect of the different treatments

This document is confidential and any unauthorised disclosure is prohibited Version 2015

Industry allocated project number

PHI allocated project number

SATI

CFPA

SAAPPA/SASPA

DFTS

Winetech

[email protected] [email protected] [email protected] [email protected] [email protected]

Tel: 021 863-0366 Tel: 021 872-1501 Tel: 021 882-8470 Tel: 021 870 2900 Tel: 021 276 0499 X X

___________________________________________________________________

FINAL REPORT (July 2016)

1. PROGRAMME AND PROJECT LEADER INFORMATION

Research Organisation Programme

leader

ARC Research Team Manager Project leader

Title, initials, surname Prof. B.K. Ndimba

Mr A. R. Mulidzi Dr. J. C. Fourie

Present position Senior Manager: Research

Research Team Manager: Soil & Water Science

Senior Researcher

Organisation, department ARC Infruitec-Nietvoorbij Private Bag X5026 Stellenbosch 7599

ARC Infruitec-Nietvoorbij Private Bag X5026 Stellenbosch 7599

ARC Infruitec-Nietvoorbij Private Bag X5026 Stellenbosch 7599

Tel. / Cell no. (021) 809 3000 (021) 809 3014 021 809 3043 E-mail [email protected] [email protected]

2. PROJECT INFORMATION

Research Organisation Project number

WW 02/21

Project title The effect of two cover crop management practices applied to cover crops, selected for their potential to bio-fumigate the soil, on the nematode and weed population, as well as grapevine performance and soil quality.

Short title

Fruit kind(s) Wine grapes, dried fruit Start date (mm/yyyy) 1/04/2009 End date (mm/yyyy) 30/09/2015

Key words

Researcher surname 2


Approved by Research Organisation Programme leader (tick box)

THIS REPORT MUST INCLUDE INFORMATION FROM THE ENTIRE PROJECT 3. EXECUTIVE SUMMARY

Objectives & Rationale Alternatives for the chemical control of soil-borne pathogens (bio-fumigation). In this study the ability of species (selected for bio-fumigation) to control nematodes and weeds, as well as their effect on biological activity, soil pathogen status and microbial population of the soil was determined Methods The soil was analysed chemically and the cover crop performance and weed control estimated. The soil nematode status and soil biological activity, as well as the microbial and pathogen status of the soil was determined. Grapevine performance was also monitored throughout the study. Key Results and Discussion Annual application of phosphate (P) lead to elevated levels in the 0-150 mm soil layer. Brassica juncea cv. Caliente199 (Caliente) and Eruca sativa cv. Nemat (Nemat) should be controlled chemically (CC) and not mechanically (MC) just before budbreak to maximize organic carbon (C). Avena sativa cv. Pallinup (oats), Sinapis alba cv. Braco (white mustard) and Brassica napus cv. AVJade (canola) increased the organic matter in the 150-300 mm soil layer.

The cover crops suppressed the winter growing weeds effectively after five seasons, with immediate control being achieved with oats and Caliente. Total suppression of Lolium species (ryegrass) was achieved with oats (CC) and Nemat (CC) after three years. A grass-spesific herbicide applied end of May 2012, terminated the dominance of ryegrass and facilitated the dominance of Erodium moschatum (musk heron’s bill). Sowing the cover crops on 23 May 2013, prevented ryegrass from regaining its dominance. After five winters, ryegrass was totally eradicated from the oats treatments, white mustard (CC) and Nemat (CC). CC improved the control of summer growing weeds. Musk heron’s bill was totally suppressed in all treatments during berry set within two seasons and ryegrass in all the CC treatments by 2011. This probably facilitated the dominance of Digitaria sanguinalis (crab fingergrass). Rynchelytrum repens (Natal red-top) lost its pre-treatment dominance during post-harvest within one season. The relatively low summer rainfall during 2010/11 resulted in the disappearance of Cynodon dactylon (common couch) and Polygonum aviculare (prostrate knotweed). The relatively high summer rainfall during the following seasons, probably allowed these two perennials to recover. MC seemed to promote crab fingergrass, common couch and prostrate knotweed during late summer.

The bio-assay indicated that Nemat can help to suppress M. javanica, while canola caused a decline in the C. xenoplax population.

During winter, the ring nematode increase observed Nemat, Caliente and oats was less than that of the weeds growing in this region. The most effective ring nematode suppression was achieved with canola (MC), white mustard (MC) and oats (CC). However, the drastic increase in the ring nematode population during summer and early autumn necessitate a follow-up treatment with a nematicide.

The cover crops did not affect the pathogen status, biological activity and microbial status in the soil or grapevine performance. However, the shoot mass and grape yield was higher where CC was applied compared to MC. Conclusion Oats, canola, Nemat and Caliente 199 should be used in cover crop rotations and controlled chemically from bud break to suppress problem weeds and ring nematodes.



4. PROBLEM IDENTIFICATION AND OBJECTIVES

There is an ever-increasing global focus on sustainability in the agricultural environment with the aim of producing healthy, good quality crops in an environment friendly manner. One of the aspects that deserve attention is the development of alternatives for the chemical control of soil-borne pathogens that has a low environmental impact. Bio-fumigation with cover crops is such an alternative. The three areas where bio-fumigation could have a positive effect in terms of Integrated Production (IP) are nematode control, control of soil-borne diseases and weed control.

The four selected cover crops produce sulphur containing secondary metabolites (glucosinolates) that are hydrolized to form isothiocyanate, which has a toxic effect on many soil-borne pathogens. The main concentration of the glucosinolates is in the flowers and the leaves of these species. The release of the active compound isothiocyanate takes place when the cell walls are damaged. To maximise the release of the isothiocyanate into the soil, the above-mentioned three species should, therefore, be slashed and incorporated into the soil directly thereafter. Eruca sativa cv. Nemat (Nemat) also releases exudates through its roots which attracts nematodes. Once the nematode feeds on the roots, the hydrolysis of the glucosinolates is activated resulting in isothiocyanite being released. The above-ground growth of this species, therefore, does not have to be incorporated into the soil and can be left on the soil surface as mulch.

As cover crop management is a biological non-selective method of weed control which may become an increasingly important tool for the control of herbicide resistant weeds, it is important to determine the weed control efficacy of the above-mentioned cover crop species under the above-mentioned two management practices applied during bio-fumigation.

Some bio-fumigant crops has been shown to cause a significant increase in the number of Pythium propagules in the soil, which in some cases caused a 6% reduction in the amount of vines established successfully compared to the untreated control.

The effect of the breakdown products of the glucosinolates on the microbial population in the soil is not known and should also be investigated, as it could have a negative effect on soil microbial activity.

The producer needs guidelines for the successful and sustainable application of biological control measures for the effective suppression of nematodes and weeds that will not impact negatively on the micro-organisms in the soil and will not promote Cylindrocarpon levels in the soil.

This study will help ensure the production of healthy, good quality grapes in an environment friendly and sustainable manner.

5. DETAILED REPORT a. PERFORMANCE CHART (for the duration of the project)

Milestone Target Date Extension Date Date completed 1. Determine the effect of the different treatments on the nematode status of the soil.

31 March 2014. 31 March 2014.

2. Determine the weed control efficacy of the different treatments.

31 March 2014. 31 March 2014.

3. Determine the effect of the different treatments on the occurrence of Cylindrocarpon in the soil.

31 March 2014. 31 March 2014.



4. Determine the effect of the different treatments on soil microbial diversity.

31 March 2014. 31 March 2014.

5. Determine the effect of the different treatments on the soil nutrient status and organic matter content.

31 March 2014 31 March 2014

6. Information dissemination: Present three papers/posters with preliminary results at a conference Present six papers/posters at the SASEV annual conference

November 2011 November 2013

May 2011-one, October 2011-one (international), November 2012-four, November 2013-one. January 2014-one, September 2014-two (international). Total 10

7. Present two talks to producers and technical personnel

September 2013

July 2011-one, September 2011-one, April 2012-one, January 2013-one, February 2013-one, April 2013-three, May 2013-five. Total 13

8. Scientific publications: Three

March 2014 September 2015 Four scientific publications, one MSc dissertation and two Hons. mini-dissertations published

9. Semi-scientific publications Three

March 2014 September 2015 Five published

b) WORKPLAN (MATERIALS AND METHODS) Experiment vineyard and layout The trial was conducted over five consecutive seasons (from 2009/10 to 2013/14) in a full-bearing, seven year old Shiraz/101-14 vineyard established on a sandy (0 to 300 mm soil layer) to sandy clay loam (300 to 600 mm soil layer) soil at Blaauwklippen farm (33°58'S, 18°50'E) near Stellenbosch in the Western Cape, South Africa (Table 1). Stellenbosch receives an average annual rainfall of 673 mm, of which approximately 73% precipitates from March to August. The Shiraz vines were spaced 1.2 m in the row and 2.5 m between rows and trained onto a Perold trellis system (Booysen et al., 1992). Fourteen treatments (Table 2) were replicated three times in a fully randomized block design. The treatments consisted of five cover crop species managed according to two management practices (10 treatments). These were compared to two treatments in which no cover crop was sown and the weeds were managed according to the above-mentioned two management practices (Weeds), as well as to two similar treatments in which a nematicide (Rugby 10ME) was applied at 15 mL/m² to the vine row (Weedsnem). Each replication plot covered an area of 81 m2. A work row and two vine rows functioned as a buffer zone between treatments in different work rows and five vines acted as a buffer zone between the experiment vines of treatment plots that were situated in the same vine row.

Seedbed preparation in the work row was done to a depth of approximately 150 mm with a disc harrow (two passes in opposite directions). The seeds, after being broadcast by hand at the seeding densities indicated in Table 2, were covered by means of shallow cultivation



Table 1. Characterisation of the 0 to 300 mm and 300 to 600 mm soil layers of the sandy to sandy loam soil in the Stellenbosch district, determined before the treatments commenced.

Soil Layer Clay

(%)

Silt

(%)

Sand

(%)

Stone

(Vol %)

pH (KCl) 1 Electrical

conductivity1

(dS/m)

Organic

C1 (%)

P (Bray II)1

(mg/kg)

K (Bray II) 1

(mg/kg)

Exchangeable cations1

(cmol(+)/kg)

Ca Mg K Na

0-300 mm 7.0 4 89 35 6.1 0.06 0.66 25 30 3.67 0.30 0.08 0.07

300-600 mm 24.0 6 70 45 5.0 0.06 0.47 9 14 2.41 0.48 0.04 0.08

1The average values of the 0 to 75 mm, 75 to 150 mm and 150 to 300 mm layers are presented.




Table 2. Treatments applied in a Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch.

Treatment number Cover Crops Management

practice

Seeding density (kg/ha)

1 Avena sativa cv. Pallinup (oats) CC1 100

2 Pallinup oats MC2 100

3 Sinapis alba cv. Braco (white mustard) CC 8

4 White mustard MC 8

5 Brassica napus cv. AVJade (canola) CC 8

6 Canola MC 8

7 Brassica juncea cv. Caliente 199 (Caliente) CC 10

8 Caliente MC 10

9 Eruca sativa cv. Nemat (Nemat) CC 5

10 Nemat MC 5

11 No cover crop (Weeds) CC NA3

12 Weeds MC NA

13 Weeds + nematicide (Rugby 10ME @15mL/m²) (Weedsnem)

CC NA

14 Weedsnem MC NA

1Full surface chemical control from grapevine budbreak to grapevine harvest . 2Chemical control in the vine row and mechanical cultivation in the work row during grapevine bud break, CC from berry set.3Not applicable. (approximately 30 mm deep) with a rotary harrow. During the 2009/10 to 2012/13 seasons, the cover crops were sown annually during early May (seeding dates varying between 4 and 10 May), after the first winter rain in excess of 16 mm. The late onset of winter rain in 2013 resulted in the cover crops not being established until 23 May. At the beginning of the trial in April 2009, a fine seedbed could not be created as a result of excessive weed growth in the work row and a slight furrow in the centre of the work row causing the vine rows to be slightly ridged. After sowing, the seeds were covered by means of a light cultivation action to ensure good seed/soil contact. The slanted soil surface caused a large percentage of the seeds to accumulate in the middle of the work row. The mechanical cultivations applied during the first year levelled the soil in the work row to the extent that seedbed preparation and the covering of the broadcast seeds were achieved over the full surface from the second season (2010/11) onwards.

The cover crops were controlled between late bloom and early seed/pod formation, which coincided with grapevine bud break. Two management practices were applied. Full surface, post-emergence weed control was achieved with glyphosate at a rate of 1.8 kg/ha (CC), where after the cover crops/weeds were left standing to be flattened by the tractor traffic during the grapevine growing season. In the treatments cultivated mechanically (MC), mechanical maceration of the cover crops was achieved by slashing the crops with a standard weed slasher and incorporating the fibre to a depth of 200 mm immediately thereafter with a disc harrow. In these treatments chemical weed control was applied to the vine row with glyphosate at a rate of 0.6 kg/ha. The mechanical incorporation of the cover crop fibre was done before the soil started drying out, as water plays an important role (hydrolysis) during bio-fumigation



(Matthiessen et al., 2004). This was, however, not always possible, as rainfall was required to ensure sufficient soil moisture in the work row. If the soil moisture level is 66% of field water capacity at the time of incorporation, irrigation or rainfall is not essential, as bio-fumigation may still be expected to take place (L. Lazzeri, personal communication, 2012). Full surface, post-emergence weed control was achieved in both the MC and CC treatments during the first week of December by applying glyphosate at a rate of 1.8 kg/ha. During late May 2012, fluasifop-butyl was applied at a rate of 1 kg/ha in all the treatments, except the two treatments in which Avena sativa cv. Pallinup (Pallinup oats) was established as cover crop, to control the problem weed Lolium species (ryegrass). Fertilisers applied To optimize biomass production, Brassica juncea cv. Caliente 199 (Caliente) and Nemat require approximately 120 kg/ha nitrogen (N) and 60 to 80 kg/ha N, respectively, depending on the fertility of the soil (D. Gies, personal communication, 2007). At the two to six leaf stages of a grain cover crop 28 kg/ha N should be applied to optimise dry matter production (DMP) (Fourie & Raath, 2008; Fourie et al., 2011). Brassica napus (canola) requires approximately 90 to 110 kg/ha N, 24 kg/ha phosphate (P) and 30 kg/ha potassium (K) to optimise biomass production on sandy to sandy loam soils (Anonymous, 2013). According to Conradie (1994), 25 kg/ha P is required to ensure a good cover crop stand, whilst the K level in the soil should be at least 40 mg/kg. However, amounts of fertilisers applied to cover crops in vineyards should not exceed the fertiliser needs of the grapevines. The P level in this sandy to sandy loam soil should be 25 mg/kg. Maintenance fertilisation with K is required at a rate of 3 kg per ton of grapes produced on soils with a K content of less than 30 mg/kg and an exchangeable K (Kex)/cation exchange capacity (CEC) saturation level of less than 4%. Therefore, the soil nutrient status was monitored throughout the trial period, to ensure that the amounts of fertilisers applied did not cause a nutrient imbalance in the grapevines.

The 30 kg/ha P broadcast during April 2011 (Table 3) increased the P levels in the 0 to 150 mm soil layer from 31 mg/kg (April 2009) to 60 mg/kg (April 2012) (Table 4). The P concentration in the 150 to 300 mm soil layer increased from 14 mg/kg (April 2009) to 23 mg/kg (April 2012), which is near the norm for vineyard soils (Conradie, 1994). Although an annual application of 25 kg/ha of P would help to ensure a good cover crop stand (Conradie, 1994; Anonymous, 2013), the amount of P applied was reduced to 15 kg/ha in May 2012 (Table 3), due to the high P concentration in the 0 to 150 mm soil layer (Table 4). Subsequently, the amount of P in the 150 to 300 mm soil layer was maintained at 24 mg/kg, but a further increase of 20 mg/kg observed in the 0 to 150 mm soil layer (Table 4) resulted in no P application during 2013 (Table 3). Table 3. Fertilisers broadcast in a Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch.

Growing season

Date Stage Amount (kg/ha) N P K

2009/10 15/06/2009 Two to six leaf stages of oats cover crop 28 0 0 2010/11 12/06/2010 Two to six leaf stages of oats cover crop 28 0 0 11/11/2010 Grapevine flowering stage 28 0 30 2011/12 28/04/2011 One week before sowing of cover crops 28 30 0 09/06/2011 Two to six leaf stages of oats 28 0 30 30/11/2011 Grapevine full bloom 28 0 0 2012/13 09/05/2012 Just after sowing cover crops 28 15 30 21/06/2012 Two to six leaf stages of oats cover crop 28 0 0 06/12/2012 Grapevine full bloom 0 0 30 2013/14 23/05/2013 Just after sowing of cover crops 28 0 30 20/06/2013 Two to six leaf stages of oats cover crop 28 0 0



From November 2010 onwards, 30 kg/ha of K was broadcast post-harvest (May/June) and during full bloom (late November/ early December). The post-harvest application was done to supply in the fertiliser needs of the cover crops (Anonymous, 2013). The full bloom




Table 4. The average phosphate (P), potassium (K), exchangeable K (Kex), as a percentage of the cation exchange capacity (CEC), and total inorganic nitrogen (inorganic Ntot) concentrations in the 0 to 75 mm, 75 to 150 mm, 150 to 300 mm and 300 to 600 mm soil layers, measured during the grapevine post-harvest period (April).

Soil layer (mm) P (Bray II) (mg/kg)

K (Bray II) (mg/kg)

Kex /CEC (%)

Inorganic Ntot

(mg/kg)

2009 2011 2012 2013 2009 2011 2012 2013 2009 2011 2012 2013 2010 2012 2013

0-75 38 77 78 104 42 66 60 75 2.04 2.51 2.79 3.32 26 40 26

75-150 24 39 42 56 26 39 40 38 1.91 1.45 3.03 2.08 21 29 22

150-300 14 22 23 24 23 33 31 28 1.88 2.28 2.99 2.17 17 22 19

300-600 9 11 13 10 14 29 25 22 1.33 2.08 2.51 2.07 15 19 19




application was done to supply in the fertiliser needs of the grapevines, which produced 8 t/ha on average, as the K (Bray II) and Kex/CEC saturation level in the soil were below 30 mg/kg and 4% (Table 4), the levels at which maintenance fertilisation with K should be applied (Conradie, 1994).

Twenty eight kg/ha N was broadcast on all the plots at the two to six leaf stages of oats as previously suggested (Fourie & Raath, 2008; Fourie et al., 2011). During the 2010/11 and 2011/12 seasons, 28 kg/ha N was applied during November (remaining within the guidelines of Conradie, 1994) to improve the performance of the grapevines. From the 2011/12 season onwards, all the N was applied post-harvest. Grapevine cultivation practices The practices conducted at this site were in accordance with the standard practices applied in South African vineyards. The vineyard was drip irrigated from December through to March. The standard pest and disease management programme used by the farm was applied. Soil chemical analyses Soil samples were taken from the 0 to 75 mm, 75 to 150 mm, 150 to 300 mm and 300 to 600 mm soil layers in all the plots. The soil was sampled from three positions for each layerdiagonally across the work row. The composite samples were analysed for pH (1.0 M KCl), electrical conductivity (EC), P and K (Bray II), exchangeable K, calcium (Ca), magnesium (Mg) and sodium (Na) and for organic carbon. The ECe was determined by saturating the soil samples with deionized water, filling a US Bureau of Soil Standards electrode cup with the saturated paste and measuring the ECe with a conductivity meter. The samples for the determination of P and K were prepared according to the Bray II method (The Non-affiliated Soil Analysis Work Committee, 1990), whereas the exchangeable cations were extracted with an ammonium acetate solution. These samples were analysed using an ICP-OES spectrometer (PerkinElmer Optima 7300 DV, Waltham, Massachusetts, U.S.A). The organic C content was determined through total combustion using a Leco Truspec® CN N analyser. The ammonium N (NH4-N) and nitrate N (NO3-N) were extracted with 1 M KCl and Its concentration in the extract is then determined colorimetrically on a SEAL AutoAnalyzer 3. Soil physical analyses Soil samples were taken from the 0 to 300 mm and 300 to 600 mm soil layers. Each depth interval was sampled at 10 randomly selected plots covering the three blocks in which the treatments were replicated. The clay, silt and sand fractions were determined on the two composite samples for each soil layer (each consisting of the soil from five of the randomly selected plots) according to the hydrometer method (Van der Watt, 1966). The average values are presented in Table 1. The soil texture classification was done by means of a texture chart (Soil Classification Working Group, 1991). Cover crop and weed dry matter production (DMP) The DMP of the cover crops and the associated weeds was determined just before grapevine bud break (end of August) and during grapevine berry set (end of November), according to the procedure described by Fourie et al. (2001).

Weed spectrum analyses The DMP of individual weed species was determined by harvesting the above-ground growth of five 0.5 m2 grids placed diagonally across the work row and 0.7 m apart. This was done just before grapevine budbreak (end of August), during grapevine berry set (end of November) and during the post-harvest period before seedbed preparation took place (early April). After the



samples were gathered in the field, the dry matter was determined as described by Fourie et al. (2001). Soil pathogen status Fungal pathogens were directly isolated from grapevine roots in April, August and December for four years from 2009 to 2012 as described by Van Coller (2004) when studying Phytophthora and Pythium species in South African vineyard soils. Segments from grapevine roots were excised and plated onto various culturing media, including Phytophthora selective medium (PH medium), Pythium selective medium (PH medium without hymexazol) and potato dextrose agar (PDA). Soil biological activity The bait–lamina test was applied. The test consisted of several sets of small plastic strips with a number of small perforations filled with a bait substance being exposed for a number of days in the field. The plastic strips are 140 mm long, 5 mm wide and 1.5 mm thick. The laminas are perforated with 16 holes spaced 5 mm apart. The holes were filled with a mixture of cellulose powder, nettle leaf powder and agar. Sixteen bait-laminas were planted per treatment plot. They were removed after 10 days and the empty holes, as well as the perforated holes were counted. The feeding activity was expressed as the total amount of holes showing feeding activity (soil biological activity index). The bait-lamina test was executed 30 days (2009), 21 days (2012) and 15 days (2010, 2011 and 2013) after the cover crops were incorporated into the soil (MC treatments) or controlled chemically and left as a mulch on the soil surface (CC treatments). The soil biological activity was monitored for a period of 20 days (two tests with duration of 10 days each).This was repeated to cover a period of 20 days. Control potential of cover cops as green manure and their host Status for Meloidogyne javanica (root-knot nematodes) and Criconemoides xenoplax (ring nematodes) Cover crops for green manure application Five cover crops, namely oats, Sinapis alba cv. Braco (white mustard), canola, Caliente and Nemat were selected to determine their potential as green manures for the suppression of M. javanica and C. xenoplax..

In the first bioassays, the cover crop biomass used was grown as part of the field trial executed at Blaauwklippen estate near Stellenbosch, Western Cape (Fourie et al., 2015; Kruger et al., 2015). The cover crops were collected at the late flowering, early pod formation stage, with some of the cultivars being slightly later on in the physiological development stage. In the repeat of the bioassay, the crop biomass was grown in pots at 25 ± 2 ̊C. Seeds from the five different cover crops were sown in six 4-L black plastic growing bags. The plants were fertilized on a weekly basis with Chemicult®, consisting of a balanced N.P.K ratio, as well as with micronutrients. The plants were watered by means of irrigation on a daily basis. Experimental procedure followed for laboratory bioassays The experimental method that was used in this assay, as is indicated in Figure 1, was based on a protocol, as described by Piedra Buena et al. (2006). The method was developed by the Agro-ecology Department of Centro de Ciencias Medioambientales (CCMA), Consejo Superior de Investigaciones Cientificas (CSIC), Madrid, Spain. Experimental procedure followed to determine host status The glasshouse trial consisted of the five cover crop species, with a tomato plant as control. A graphical presentation of the experimental layout is indicated in Figure 2. For each host there were 10 replicates. After the plants had been grown for approximately 40 days, they were either inoculated with the eggs of M. javanica, or soil-infested with C. xenoplax, according to a predetermined concentration. The plants were arranged in a completely randomized design. Meloidogyne javanica inoculum Tomato plants, inoculated with eggs of M. javanica, were grown in a glasshouse for four months. To obtain the eggs, the roots were carefully removed from the soil. After being washed and cut up into 2-cm pieces, they were immersed in 250 ml of 0.5% sodium chloride solution (NaOCl),



which was added to a 500-ml Schott bottle and shaken vigorously for 4 min. The contents of the bottle were then passed through a 75-µm pore (200-mesh) sieve, nested within a 38 µm-pore sieve (500-mesh), and thoroughly rinsed with a stream of water. The eggs that were collected on the 38 µm-pore sieve were washed into a beaker. The roots were returned to the bottle, to which water was added, whereupon the process was repeated. The nematode egg concentration was determined, using the technique described by Navon and Ascher (2000). Five 10-ml drops of a suspension of nematodes in a specific volume were placed on a glass slide, and the number of nematodes counted in 50 µl. This was repeated five times, with the volume of water being diluted to the concentration used as inoculum.

Figure 1. Graphical layout of the protocol used for the Meloidogyne javanica and Criconemoides xenoplax bioassays that were conducted to determine the impact of green manure on nematode suppression. Criconemoides xenoplax inoculum The peach rootstock Atlas, established in 25 L-sized plastic pots, was inoculated with C. xenoplax approximately 24 months before the start of the trial. The plants were kept in a glasshouse at a



temperature of <25⁰C. A soil auger was used to take a 100 ml soil sample from the roots of these pots. The soil was washed through a 200-mm sieve into a 10-L bucket. While stirring, the bucket was three-quarters filled with soil. After leaving the soil in the bucket for one minute, it was then poured through two nested sieves, with one being of 53-µm pore size, and the other of 45-µm pore size. The contents were then washed into a glass beaker. The process was repeated, with the contents first being left for 15 seconds to settle, and then being re-poured through the sieves, as described above. The content, washed from the soil, was centrifuged for 5 min at 3 000 rpm. The supernatant was then discarded, and each tube was filled with a sugar solution and centrifuged for 1 min. The content of the tubes was poured through a 45-µm sieve and washed to remove the sugar solution. The nematodes were then collected from the sieve and washed into a 100-ml beaker (Jenkins, 1964). The suspension was left for 30 min for the nematodes to settle to the bottom, after which the supernatant was

Figure 2. Experimental layout of cover crop host trials for Meloidogyne javanica and Criconemoides xenoplax to determine the susceptibility of the different cover crops.



siphoned off to a volume of 20 ml. The contents of the beaker were brought into suspension, using air from a fish pump, and 2 ml of the contents were counted out, using Peter’s slides, and a Leica 2000 research microscope. A soil concentration of C. xenoplax was determined to obtain the desired amount of nematodes for the inoculation of plants in the glasshouse trials. Effect of green manure on Meloidogyne javanica A total of 700 g sterilized medium, consisting of bark and sand, was added to sealable plastic bags. The medium was inoculated with 1000 M. javanica eggs, and mixed, so as to obtain an even distribution of the eggs in the medium. The green manure (biomass of the cover crops) was added to the inoculated medium. The control treatment was inoculated with only nematode eggs, without the addition of green manure. Ten bags were used in each treatment. A total of 30 g of cover crop plant material, consisting of roots, stems and leaves in 75 ml water, was macerated in a food blender for 10 sec. The plant material was then added to the inoculated medium in the plastic bags. The content of the bags was then mixed and left in a growth chamber at 25⁰C for 14 days, after which it was placed in pots, to which susceptible tomato (Solanum lycopersicum cv. Moneymaker) seedlings were added. The pots were placed in a glasshouse <25⁰C in a completely randomized design. After 80 days, the experiment was terminated, whereupon each plant was carefully removed, and the roots were rinsed off with water. Each root system was inspected, and a root galling index was used to determine the amount of M. javanica infestation that was present in the roots. This gall evaluation was done on a scale of 0 to 5, as previously described.

The same protocol as indicated in Figure 2 was followed during the repeat bioassay. During the flowering, early pod formation stage, 30 g of the biomass, consisting of leaves and stems. The pots were left for 142 days, and then evaluated for root gall formation on the tomato roots. The duration of this period was longer than was suggested in the protocol, but, as root gall formation had not yet taken place in the control pots, the decision was made to leave the plants until sufficient root gall formation could be evaluated in the control treatment. Effect of green manure on Criconemoides xenoplax The soil used for the C. xenoplax bioassay was first collected at the field trial site, and then sieved and heat sterilized (55⁰C for 24 h). A total of 500 g of the sterilized medium was then placed in sealable plastic bags. A total of 200 ml of the growing medium, representing an estimated amount of 2500 C. xenoplax juveniles, upon being placed in the same plastic bags, was then thoroughly mixed. Six treatments were undertaken, consisting of five cover crops and one control crop. The green manure was added to the inoculated medium. The control treatment consisted of sterilized medium, inoculated with the C. xenoplax, and without green manure.

Plant material (10 g), consisting of roots, stems and leaves, was macerated, using a pair of scissors. It was then added to the plastic bags containing the sterilized medium and C. xenoplax. Water (25 ml) was added to the plastic bags. The plastic bags were then placed in a temperature- controlled chamber at 25⁰C for 14 days, after which the evaluation was done, using the same extraction technique as described above, using 250 ml soil. For each treatment, there were five replicates.

In the second bioassay, sterilized medium, consisting of bark and sand, was used as the medium for the inoculation of C. xenoplax. A total of 600 g of the sterilized medium was placed in sealable plastic bags. A total of 75 ml water was added to the medium before inoculation of the nematodes. Thereafter, 100 ml of growing medium, representing 2500 C. xenoplax, was placed in the same plastic bags, in which it was thoroughly mixed. The same treatments were conducted as in the first bioassay, but with 10 repetitions per treatment. Plant biomass, consisting of leaves and stems, was harvested after approximately 2 months. During the flowering, early pod formation stage, 30 g of the plant material was cut, in approximately 10 sec, into fine pieces, each smaller than 1 × 1 cm, by means of a food processor, and then applied to the 600 g of inoculated medium. The cut-up green plant material was thoroughly mixed with the inoculated soil. The bags were then placed in a temperature-controlled chamber at 25°C for 28 days. Afterwards, the C. xenoplax numbers present were determined, using the same extraction technique as is described above.



Host status of cover crops for Meloidogyne javanica The bioassay protocol and experimental layout, as described above, were followed for both the M. javanica crop host bioassays, except that, in the first trial, 4-L growing bags were used, whereas, in the second trial, 700-ml growing bags were used. The plants were inoculated with 4000 M. javanica eggs in trial 1, and with 1000 eggs in trial 2. In both trials, the plants were left to grow for 60 days before a root gall evaluation was conducted. Host status of cover crops for Criconemoides xenoplax The same trial layout as described in Figure 2 was used in the C. xenoplax bioassays. In the first trial, 200 ml of soil, representing 2500 C. xenoplax, was used to inoculate the plants. The crops were grown for 85 days before the C. xenoplax evaluation was undertaken. In the second trial, the 700-ml growing bags that were used to grow the cover crops were inoculated with 100 ml of medium, representing 2500 C. xenoplax. In each trial, the bags inoculated only with C. xenoplax, without any cover crop, were included. An additional control treatment, using tomato plants as the host, was also inoculated with C. xenoplax. Following the inoculation, the plants were grown for 92 days, after which the evaluation was done. Evaluation of Meloidogyne javanica host status After termination of the experiment, each plant was carefully removed from the bags, and the roots rinsed with water. Each root system was carefully inspected, and a root galling index was used to determine the amount of M. javanica infestation present in the roots. This gall evaluation was done on a scale of 0 to 5, as adapted from the technique used by Hussey and Janssen (2000), where 0 = no galls, 1 = 1 to 10 galls, 2 = 10 to 50 galls, 3 = 50 to 100 galls, 4 = >100 galls, and 5 = covered with galls. According to the mean gall classification, the cover crops were then classed as good hosts, maintenance hosts, or poor hosts for M. javanica. A classification of between 0 and 2 indicated a poor host, between 2 and 4 indicated that they could be used as maintenance crops, and between 4 and 5 indicated good host status. The root systems were visually inspected, using a Leica MZ7 stereo microscope that was fitted with a camera to determine the formation of egg masses. The egg masses were then removed and left for 24 h in a glass crucible to determine their hatching. Evaluation of Criconemoides xenoplax host status The soil from each plant was carefully shaken from the roots, and thoroughly mixed. Of the soil, 250 cm3 was washed using the same technique sugar flotation technique (Jenkins, 1964) for determining the inoculum concentration as was previously described. The number of nematode present was then counted. The effect of the cover crops and management practices on the plant-parasitic nematodes in the vineyard Extraction and identification of nematodes To determine the effect of the selected cover crops and cover crop management practices on the nematode numbers, a composite soil sample was taken from the 0-250 mm soil layer of each plot at the beginning of April (before the re-establishment of the cover crops), as well as day 0 (just before the management practices were applied), day 15, day 30 and day 60, after application of the management practices. The samples were taken in the work row or inter-row, as well as in the vine row and analysed separately. Each sample consisted of five subsamples taken diagonally across the work row, as well as underneath the vines in the vine row. Nematodes were extracted from the soil, using a sugar centrifugation technique, based on the method used by Kleynhans et al. (1996).

Soil samples were mixed in the laboratory, and the nematodes were extracted from a 250 ml subsample using a sugar flotation technique (Jenkins, 1964). The nematodes were then counted and identified, using a light microscope, according to the technique described by Kleynhans et al. (1996). Soil microbial activity



DNA was extracted within 24 h of sample collection using the ZR Soil Microbe DNA kit (Zymo Research, California, USA). ARISA PCR reactions were performed on the genomic DNA using fungal and eubacterial specific primer sets to evaluate its application in automated ribosomal internal transcribed spacer (ITS) analysis (ARISA). Eubacterial specific primers, ITSReub and FAM (carboxy-fluorescein) labelled ITSF, were used to determined to bacterial diversity with ARISA (Cardinale et al. 2004). PCR reactions were done using a GeneAmp PCR System 2400 (AppliedBiosystems, USA). The reaction mixture contained 0.5 μl of the purified genomic DNA extracted from soil, 500 nM of each primer and 5 µl of 2X KapaTaq Readymix (KapaBiosystems, South Africa) in a total volume of 10 µl. The PCR conditions consisted of an initial denaturing step of 3 min at 95 °C followed by 40 cycles of 95 °C, for 30 s, 51 °C for 30 s and 72 °C for 30 s. The reaction was completed with a final extension at 72 °C for 5 min and then cooled and held at 4 °C. PCR for each sample was performed in triplicate and pooled to eliminate background noise form the ARISA profile and reduce the PCR variability occurring. PCR samples were separated on a 1% agarose gel, stained with Ethidium Bromide and visualized using ultra violet light.

The PCR products were run on an ABI 3010xl Genetic analyser to obtain an electropherogram of the different fragment lengths and fluorescent intensities. ARISA samples were run with ROX 1.1 size standard which varied from 20 - 900 bp (Slabbert et al. 2010). ARISA data was analysed using Genemapper 4.1 software. The software converted fluorescence data to an electropherogram and the peaks which represented fragments of different sizes are termed operational taxonomic units (OTU). Only fragment sizes larger than 0.5% of the total fluorescence, ranging from 100 to 1000 base pairs in length was considered for analysis. A bin size of 3 bp for fragments below 700 bp and 5 bp for fragments above 700 bp’s was employed to minimise the inaccuracies in the ARISA profiles (Brown et al. 2005; Slabbert et al. 2010). Sequencing using Ion Torrent PCR amplification of the DNA was performed using primers targeting the variable V4 to V5 region of the 16S rRNA gene. The forward primers were modified with specific PGM adaptor sequences, barcodes and barcode adapters for one-way multiplex sequencing (Ion Torrent Life Technologies, Carlsbad, USA). The total reaction volume (20 µl) contained 12.5 µl of 2 x Kapa KiFi HotSart ReadyMix (Kapa Biosystems, South Africa), 0.25 µM of each primer and 1 µl DNA. PCR reactions were preformed in a GeneAmp® PCR System 9700. Amplification conditions consisted of an initial denaturing step at 95 °C for 5 min followed by 35 cycles of 98 °C for 20 s, 75 °C for 15 s and 72 °C for 30 s. The reaction was completed with a final extension at 72 °C for 1 min and the samples were held at 4 °C. DNA was purified and size selected using the E-Gel® SizeSelectTM (Life Technologies, Carlsbad, USA) system. DNA concentration and size distribution of the PCR products were verified using the Agilent High Sensitivity DNA Kit on the 2100 Bioanalyzer (Agilent Technologies, USA). The final concentration of each sample was adjusted to 20-25 pM and all samples were pooled. This pooled sample was used for emulsion PCR according to the Ion PGM® Template OT2 400 Kit (Life Technologies, Carlsbad, USA). After enrichment, samples were loaded on an Ion 318TM Chip for sequencing (Ion Sequencing Kit User Guide v2.0, Life Technologies) using the Ion PGM® Sequencing 400 Kit on the PGMTM (Ion Torrent, Life Technologies). Grapevine performance Shoot mass The shoots mass was determined during pruning by collecting the shoots from the 10 experiment vines and weighing then directly thereafter. This occurred annually early in August. Grape yield Grapes were harvested when the sugar concentration was approximately 23°B during the 2009/10 harvest, approximately 21°B during the 2010/11 harvest and 24°B during the 2011/12 and 2012/13 harvests (Table 5).The grapes from the 10 experiment vines per experiment plot



were pooled and weighed. This was done on 23 February during 2010 and 2011, 15 March 2012 and 11 March 2013.

Table 5. The sugar content of the juice during harvest, as measured 23 February 2010 and 2011, as well as 15 March 2012 and 11 March 2013.

Treatment Sugar content of the juice (°B)

2010 2011 2012 2013 1. Avena sativa cv. Pallinup (oats), CC1 23.2 20.3 24.0 23.8 2. Oats, MC2 22.7 21.1 23.9 24.3 3. Sinapis alba cv. Braco (white mustard), CC 23.6 21.0 25.0 24.0 4. White mustard, MC 22.5 20.5 24.4 24.4 5. Brassica napus cv. AVJade (canola), CC 23.5 20.7 24.0 24.1 6. Canola, MC 23.3 21.4 24.0 24.1 7. Brassica juncea cv. Caliente 199 (Caliente), CC 23.7 21.5 23.9 24.5 8. Caliente, MC 23.2 21.2 23.7 24.6 9. Eruca sativa cv. Nemat (Nemat), CC 23.2 21.5 24.2 23.9 10. Nemat, MC 23.4 20.6 24.3 23.9 11. No cover crop (Weeds), CC 23.0 21.0 24.5 24.2 12. Weeds, MC 22.6 20.7 24.1 24.5 13. Weeds + nematicide (Weedsnem) 23.1 20.8 24.4 24.4 14. Weeds, nematicide, MC 23.0 20.5 24.1 24.1 LSD (p≤0.05) 0.1 0.8 0.63 NS4

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set. 3Data differs significantly at the 10% level. 4Data does not differ significantly at the 10% level. Petiole and leaf analyses Leaf analyses were carried out over four seasons (2009/10 to 2012/13). Leaves were collected at full bloom from locations directly opposite clusters. Leaves and petioles were separated immediately after sampling. The samples were washed with a Teepol solution, rinsed with de-ionised water and dried over night at 70oC in an oven. The dried samples were then milled and ashed at 480oC, shaken up in a 50:50 HCl (32%) solution for extraction through filter paper (Campbell & Plank, 1998; Miller, 1998). The cation and micro nutrient (B, Fe, Zn, Cu, Mn) content of the extract was measured with a Varian ICP-OES optical emission spectrometer. Total N content of the ground samples was determined through total combustion in a Leco N-analyser. Juice analyses A representative sample (approximately one bunch per experimental vine) from each plot was crushed in a hydraulic press. Free run juice was analysed for sugar content (temperature




compensated Abbé refractometer), total titratable acid (50 mL juice titrated with 0.333 M NaOH to pH 7.0 and expressed as g tartaric acid/L) and pH (654 Metrohm pH meter). Total juice N was determined using an automated colorimetric method (The Non-affiliated Soil Analysis Work Committee, 1990), following digestion with selenous acid/sulphuric acid. Total P, K, Ca and Mg concentrations in the juice were determined by atomic absorption spectrophotometry, following digestion with nitric acid/perchloric acid. Experimental wines Experimental wines were prepared from the grapes of each of the 14 ttreatments, as described by Fourie et al. (2006) during 2011. The wines were stored at 14°C for three months before evaluation. Sensory evaluation was carried out by an experienced panel of 14 members on a ten point scorecard, similar to that described by Tromp and Conradie (1979). The wines were presented in coded form and evaluated for overall wine quality, as well as for aroma and taste. Statistical analyses Soil analyses, cover crop and weed DMP, soil biological activity, grapevine performance parameters The experiment was a complete randomized block design with fourteen treatments replicated five times and repeated for five consecutive seasons (years). The data were tested for normality (Shapiro & Wilk, 1965), found to be acceptably normally distributed, and subjected to analysis of variance. Analyses of variance were performed separately for each season, using Statistical Analysis System (SAS, 1990). Student’s t least significant difference (LSD) was calculated at the 5% and 10% significance level to facilitate comparison between the treatment means. Control potential of cover cops as green manure and their host Status for Meloidogyne javanica (root-knot nematodes) and Criconemoides xenoplax (ring nematodes) All the laboratory experiments conducted were repeated on different test dates. All statistical analyses were performed using the STATISTICA, version 10, data analysis software system (StatSoft, Inc., 2011). The data that were obtained from the bioassays were analysed using an analysis of variance (ANOVA), regarding the trial test date and relevant treatments as separate factors. If the data were not normally distributed, a non-parametric analysis, using the Kruskal-Wallis test, was performed. Plant-parasitic nematodes in the vineyard Ten experimental grapevines per plot were used for measurements. An analysis of variance was performed separately for each season, using Statistical Analysis System (SAS, 1990). Student’s t least significant difference (LSD) was calculated at the 5% and 10% significance level to facilitate comparison between treatment means. The Shapiro-Wilk test was performed to test for non-normality (Shapiro & Wilk, 1965). Soil microbial activity ARISA The peak heights were used to calculate the diversity indices for each ARISA profile using Microsoft Excel™ software. The Shannon-Weaver (H) index was calculated for each sample and each plot to determine the disorder in the species distribution of the community. The increase of beta diversity was determined over the different samples, plots and sites. The Whittaker (βw) index for beta diversity was determined over all scales and comparisons made between samplings (Whittaker 1972).

The Whittaker similarity index was calculated for bacterial and fungal profile data, between all plots. The distance relationship between the samples was illustrated by performing a complete linkage cluster analyses using the Whittaker (Sw) similarity indices (Hewson et al. 2006). After



initial grouping with cluster analysis the significance of the groupings were tested by performing non-parametric analysis of similarity analysis (ANOSIM) with 10 000 permutations (Clarke 1993). Sequence processing and statistical analysis Sequence data were analyzed using Mothur v. 1.37 (Schloss et al. 2009), following the SOP tutorial (http://www. mothur.org/wiki/Schloss_SOP) with some modifications. The reads were filtered and trimmed and only sequence reads excluding 150 base pairs in length were used for further analysis. The analyzed reads were normalized according to the total number of reads. The bacterial reads were aligned and classified against the RDP Silva database and classification. The bacterial classification was done to genus level. Community ordination was performed based on the normalized reads classified to genus level. Factor analysis was used to represent the community ordination. The factorial distance matrix was used to test the vine and working row groups priori using Analysis of similarity (ANOSIM). Bacterial taxa associated with the bench and working rows were identified using an indicator analysis approach using the IndicSpecies package (De Caceres 2015) on the R software package v 3.2.5. Alpha and β-diversity metrics are commonly used in microbial ecological studies and give valuable information with regards to the microbial community structure (Jost, 2007). c) RESULTS AND DISCUSSION Soil nutrient status The general trend in the levels of P, K and N have already been discussed under the heading ‘Fertilisers applied’ on page 7 and presented in Table 4. The organic carbon (C)) in the different soil layers at the beginning and end of the study is presented in Table 6. The organic C differed between treatments in the 0-75 mm (2009 and 2013), 150-300 mm (2013) and 300-600 mm (2013) soil layers. Before the treatments were applied, the organic C in the treatment in which MC (see Table 2 for detail) was applied to white mustard, as well as both treatments in which Caliente was established as cover crop was lower than that of the two canola treatments, white mustard (CC) and oats (MC) (Table 6). At the end of the trial (2013), the organic C was lower in the 0-75 mm soil layer of the Caliente and Nemat treatments than that of Weedsnem (MC). Despite this, the percentage increase observed in the Caliente and Nemat treatments exceeded that of the canola treatments. The results indicate that canola is not the preferred choice to build up the organic matter in these sandy top soils. Caliente and Nemat should also not be incorporated into the soil, but rather be controlled chemically during budbreak to promote an increase in the organic C of these sandy top soils. Although the organic C in the 75-150 mm soil layer did not differ between treatments, the increase in organic C observed for the cover crop treatments was, with the exception of canola and Caliente (MC), higher than that of the treatments in which no cover crop was established. This supports the trend observed for the 0-75 mm soil layer. The organic C measured in the 150-300 soil layer at the end of the trial (2013) tended to be higher in the treatments where oats, white mustard and canola were established than in the other treatments. This may be an indication that the roots of these cover crops are making a contribution to the organic matter content in the deeper soil layers. Although significant differences in organic C did occur between treatments in the 300-600 mm soil layer, no definite trends were observed. Cover crop performance and weed control ability Cover crop performance During 2009, oats, white mustard and Caliente produced similar amounts of dry matter, whereas Nemat performed poorer than these species (Table 7). The DMP of all the cover crop species, with the exception of oats (CC), was higher during 2010 than in 2009. This was attributed to the improved seedbed, as well as the higher rainfall that occurred during the first two weeks of May (Table 8). That August 2010 was being slightly warmer than August 2009 (Table 9), could also have contributed to the observed increase in DMP. The 0.55 to 2.62 t/ha increase in dry matter observed for the small-seeded white mustard, canola, Caliente and Nemat (Table 7) confirmed the importance of proper seedbed preparation when these species are considered for cover crop management.




Table 6. The organic carbon (C) levels in the 0 to 75 mm, 75 to 150 mm, 150 to 300 mm and 300 to 600 mm soil layers, measured during the grapevine post-harvest period (April).

Treatment

Organic C (%) 0-75 mm soil layer 75-150 mm soil layer 150-300 mm soil layer 300-600 mm soil layer

2009 2013 % Increase 2009 2013 %Increase 2009 2013 % Increase 2009 2013 % Increase

1. Avena sativa cv. Pallinup (oats), CC1 0.98 1.41 43.88 0.54 1.21 124.00 0.51 0.81 58.82 0.48 0.66 37.50

2. Oats, MC2 1.07 1.46 36.45 0.79 1.17 48.10 0.71 0.99 39.44 0.56 0.62 10.71

3. Sinapis alba cv. Braco (white mustard), CC 1.01 1.35 33.66 0.77 1.26 63.64 0.52 0.87 67.31 0.44 0.78 77.27

4. White mustard, MC 0.74 1.27 71.62 0.64 1.30 103.13 0.39 0.73 87.18 0.56 0.57 1.79

5. Brassica napus cv. AVJade (canola), CC 1.27 1.36 7.09 0.83 0.87 4.82 0.66 0.76 15.15 0.44 0.49 11.36

6. Canola, MC 1.22 1.27 4.10 0.82 1.14 39.02 0.58 0.96 65.52 0.61 0.66 8.20

7. Brassica juncea cv. Caliente 199 (Caliente), CC 0.73 1.02 39.72 0.67 0.97 44.78 0.46 0.58 26.09 0.38 0.46 21.05

8. Caliente, MC 0.71 0.79 11.27 0.67 0.85 26.87 0.51 0.61 19.61 0.49 0.49 0

9. Eruca sativa cv. Nemat (Nemat), CC 0.82 1.04 26.82 0.46 1.04 126.09 0.39 0.59 51.28 0.49 0.49 0

10. Nemat, MC 0.95 1.05 10.53 0.57 0.92 61.40 0.52 0.60 15.38 0.31 0.40 29.03

11. No cover crop (Weeds), CC 0.88 1.26 43.18 0.53 0.75 41.51 0.55 0.61 10.91 0.43 0.75 74.42

12. Weeds, MC 0.87 1.58 81.61 0.84 1.01 20.24 0.51 0.60 17.65 0.33 0.41 24.24

13. Weeds + nematicide (Weedsnem), CC 0.94 1.77 88.30 0.62 0.87 40.32 0.54 0.64 18.52 0.48 0.57 18.75

14. Weedsnem, MC 0.98 1.68 71.43 0.76 1.04 36.84 0.57 0.67 17.54 0.54 0.54 0

LSD (p≤0.05) 0.32 0.68 NA3 NS4 NS NA NS 0.335 NA NS 0.19 NA

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set. 3Not applicable. 4Data does not differ significantly at the 10% level. 5Data differs significantly at the 10% level.




Table 7. Effect of soil management on cover crop performance and control of winter growing weeds measured at the end of August.

Treatment

Dry matter production (t/ha)

2009 2010 2011 2012 2013

Cover crop Weeds Cover crop Weeds Cover crop Weeds Cover crop Weeds Cover crop Weeds

1. Avena sativa cv. Pallinup (oats), CC1 3.29 0.33 2.48 0.18 5.66 0.01 5.60 0.13 5.73 0.09

2. Oats, MC2 2.10 0.41 2.49 0.25 2.52 0.81 5.08 0.30 5.98 0.12

3. Sinapis alba cv. Braco (white mustard), CC 2.70 0.38 4.96 0.01 4.48 1.06 3.49 0.20 3.57 0.02

4. White mustard, MC 2.57 0.37 3.21 1.20 5.12 0.72 3.01 0.46 2.66 0.60

5. Brassica napus cv. AVJade (canola), CC 1.81 0.69 2.36 0.66 4.39 0.66 0.87 0.34 3.06 0.30

6. Canola, MC 1.64 1.09 2.22 1.07 3.98 1.05 1.71 1.93 3.79 0.20

7. Brassica juncea cv. Caliente 199 (Caliente), CC 2.37 0.36 3.08 0.16 5.23 0.04 2.91 0.11 2.36 0.20

8. Caliente, MC 2.43 0.47 3.08 0.35 5.62 0.27 2.75 0.32 2.02 0.29

9. Eruca sativa cv. Nemat (Nemat), CC 0.71 0.92 3.33 0.01 5.13 0.36 2.24 0.32 2.07 0.17

10. Nemat, MC 0.95 0.63 1.62 0.90 1.79 2.45 1.57 1.16 1.41 0.57

11. No cover crop (Weeds), CC 0 3.74 0 3.15 0 3.69 0 3.51 0 4.49

12. Weeds, MC 0 3.30 0 3.45 0 4.58 0 3.39 0 3.51

13. Weeds + nematicide (Weedsnem), CC 0 3.08 0 3.79 0 2.87 0 3.40 0 4.10

14. Weedsnem, MC 0 2.38 0 3.28 0 4.57 0 2.80 0 4.59

LSD (p≤0.05) 1.18 1.23 1.03 0.86 1.39 1.55 1.08 1.07 1.41 1.35

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set.




Table 8. Winter rainfall for the period April to August measured over five seasons at Alto weather station, close to the trial site.

Period Winter rainfall (mm)

2009 2010 2011 2012 2013 1 April to 2 April 0 0 1 0 15 3 April to 9 April 2 11 0 51 6 10 April to 16 April 0 0 0 2 15 17 April to 23 April 21 13 2 0 25 24 April to 30 April 23 0 42 24 1 1 May to 7 May 14 37 29 36 8 8 May to 14 May 6 75 0 1 6 15 May to 21 May 59 0 0 22 1 22 May to 28 May 7 28 50 23 40 29 May to 4 June 34 1 35 10 83 5 June to 11 June 28 33 10 70 23 12 June to 18 June 34 59 44 5 21 19 June to 25 June 46 6 50 23 35 26 June to 2 July 4 12 29 17 1 3 July to 9 July 2 7 2 50 2 10 July to 16 July 65 56 0 25 7 17 July to 23 July 10 5 0 44 74 24 July to 30 July 5 1 15 17 34 31 July to 6 August 33 0 30 47 20 7 August to 13 August 24 25 18 41 67 14 August to 20 August 33 6 10 47 52 21 August to 27 August 6 35 24 24 18 28 August to 31 August 0 4 13 16 88

Total winter rainfall 456 414 404 595 642

The DMP of all the species, with the exception of white mustard (CC), was higher in the 2011/12 season, compared to that of the previous season (Table 7). This was attributed to the additional P and N applied one week before sowing, as well as the K applied at the two to six leaf stages (Table 3), contributing to a more acceptable level of K, especially in the 0 to 75 mm and 75 to 150 mm soil layers (Table 4). Although May 2011 was 0.6°C warmer than May 2010, the average temperatures of the two cover crop growing seasons were similar (Table 9), indicating that temperature made a minor contribution to the observed increases in DMP during this season (Table 7). Although it did not rain during the second and third week after the cover crops were sown, the 71 mm rain that fell between 24 April and 7 May 2011 (Table 8), seemed sufficient to ensure the successful germination of the cover crop seeds and sustain growth during the first



three weeks. The DMP of the four broadleaf cover crops that were selected for their bio-fumigation properties was lower than that of oats during the 2012/13 season and produced less fibre than during the previous two seasons (Table 7). This decline in performance occurred despite an application of N, P and K just after the crops were sown (Table 3). The observed trend was attributed to the May 2012 temperatures being 0.6°C and 1.2°C lower than they were in May 2010 and in May 2011, respectively, as well as the average temperature from May 2012 to August 2012 being approximately 1.4°C lower than that of the previous two seasons (Table 9). This indicated that the four broadleaf species were more sensitive to lower temperatures than oats. Although the cover crops could only be sown late (23 May 2013), the DMP of oats still improved slightly, compared to 2012 (Table 7). It seems that the relatively high rainfall during the first five weeks following the sowing of the cover crops (Table 8), the temperatures during May, July and August being higher than those of the previous season (Table 8), as well as the K being higher in the 0 to 75 mm and 75 to 150 mm soil layers (Table 4), contributed to the observed increase in DMP (Table 7). The aforementioned edaphic conditions also resulted in the DMP of canola during 2013 being higher than in the 2012 season. However, white mustard, Caliente and Nemat performed slightly poorer in 2013 than in the previous season, indicating that these species need to be sown earlier. Although the DMP of the broadleaf cover crops was lower than that of oats for the second consecutive season (Table 7), it was, with the exception of Nemat (MC), similar to the DMP levels reported by Fourie et al. (2001) for oats and Secale cereale (rye) established in early May on a medium textured soil near Stellenbosch that was irrigated over the full surface by means of micro-sprinklers. Table 9. Average monthly winter air temperatures from May to August measured over five seasons at Alto weather station, close to the trial site

Month Temperature (°C)

2009 2010 2011 2012 2013

May 16.2 16.0 16.7 15.5 17.5

June 14.8 14.8 14.2 14.1 13.8

July 15.2 14.5 15.3 13.2 14.2

August 14.3 14.8 14.5 12.3 13.1 Suppression of winter growing weeds Despite differences in DMP, all the cover crop species, except for the canola in the MC treatment during 2012, suppressed the winter growing weeds throughout the study (Table 7). The winter growing weeds were effectively suppressed (less than 10% of the weed stand measured in the treatments in which no cover crop was sown) by the CC treatments of oats, Caliente and white mustard throughout the study, with the exception of white mustard (CC) during 2011. Effective winter weed suppression was achieved with Nemat (CC) during 2010, while the same result was achieved with Caliente (MC) during 2011. All the cover crop treatments suppressed the winter growing weeds effectively during 2013 (fifth season which the treatments were applied), indicating that all the species selected for their bio-fumigation properties could provide in effective winter weed suppression over the medium term. Suppression of summer growing weeds The two management practices applied, as well as the different cover crop species, had no significant effect on the weed stand measured at the end of November 2009 (Table 10). Although the stand of summer growing weeds differed significantly between treatments during the following three seasons (2010, 2011 and 2012), none of the cover crop treatments reduced the weed stand significantly compared to the treatments in which no cover crop was sown (Weeds and



Weedsnem). However, the weed stand in the CC treatments of oats and mustard was lower than in the corresponding MC treatments in November 2010. Although not significant, this trend was also observed for canola, Caliente and Nemat. During the 2011 and 2012 seasons, a similar trend were observed for all treatments, except for white mustard and Caliente during 2011, and Nemat during 2012. During the last-mentioned season, the trend was significant for the oats, canola, Caliente and Weeds treatments. The observed trend was attributed to the presence of a surface mulch in the CC treatments, as well as to the mechanical cultivation applied during September in the MC treatments which may have promoted the germination of weeds during early summer. Table 10. Effect of different soil management practices on the stand of summer growing weeds measured at the end of November.

Treatment Dry matter production (t/ha) 2009 2010 2011 2012

1. Avena sativa cv. Pallinup (oats), CC1 1.00 0.21 0.06 0.07

2. Oats, MC2 0.85 0.79 0.29 0.81

3. Sinapis alba cv. Braco (white mustard), CC 0.98 0.10 0.24 0.20

4. White mustard, MC 0.85 0.60 0.03 0.47

5. Brassica napus cv. AVJade (canola), CC 0.65 0.18 0.02 0.17

6. Canola, MC 0.78 0.50 0.19 0.53

7. Brassica juncea cv. Caliente 199 (Caliente), CC 0.73 0.54 0.33 0.15

8. Caliente, MC 0.45 0.66 0.15 0.60

9. Eruca sativa cv. Nemat (Nemat), CC 0.69 0.17 0.01 0.59

10. Nemat, MC 0.57 0.38 0.07 0.51

11. No cover crop (Weeds), CC 0.61 0.56 0.04 0.10

12. Weeds, MC 1.24 0.49 0.78 0.64

13. Weeds + nematicide (Weedsnem), CC 0.72 0.53 0.14 0.43

14. Weedsnem, MC 1.13 0.45 0.52 0.70

LSD (p≤0.05) NS3 0.41 0.37 0.33 1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine bud break, full surface chemical control from berry set. 3Does not differ significantly, 10% level. Effect of treatments on the composition of the winter weed population 2009



At the end of the first winter in which the cover crops were established in the grapevine inter-row (work row), the ryegrass was either the most dominant or second most dominant species in all the treatments, with the exception of oats (CC), white mustard (CC) and Caliente (MC) (Table 11). The stand of ryegrass in (CC) and white mustard (CC) was lower than that of the Weeds and Weedsnem treatments in which no cover crop was sown, indicating effective suppression of the species at this time. Raphanus raphanistrum (wild radish) was the most dominant species in the two oats treatments, while Oxalis pes-caprae (yellow sorrel) dominated the CC treatments of white mustard, canola, Caliente and the two Nemat treatments. Wild radish and yellow sorrel are easy to control chemically, while ryegrass has the tendency to become resistant to glyphosate and paraquat, as well as other grass-specific herbicides. The Vicia species dominated Caliente (MC) and white mustard (MC), with the stand in Caliente (MC) being significantly more than that observed for all the weeds in all the treatments, with the exception of ryegrass in Weeds (MC). The Vicia species, however, are N-fixers and also used as cover crops on sandy soils. 2010 Ryegrass dominated all the treatments,in which MC was applied, with the exception of oats (MC) (Table 12). The ryegrass stand in the MC treatments of a cover crop was also higher than that of the CC treatment of the same cover crop, with the exception of oats. Although not significant, the same trend was, however, observed for oats as well. The ryegrass stand in Weeds (MC) and Weedsnem (MC) was also higher than that of Weeds (CC) and Weedsnem (CC). This is an indication that the weed control method applied during budbreak impacted on the ryegrass stand during the following winter. The ryegrass stand in the treatments where the cover crops were combined with CC, as well as oats (MC) was lower than that of all the treatments in which no cover crop was sown. This is an indication that oats per se suppressed the ryegrass effectively, whereas the other species had to be combined with chemical control during budbreak to achieve effective suppression. Similar to the 2009 season, wild radish was the most dominant species in the two oats treatments. This weed became more dominant in the canola, Nemat and Weedsnem treatments, while becoming the most dominant species in Weeds (CC). During this season, the stand of yellow sorrel decreased in all the treatments. In white mustard (CC) it was reduced from being the most dominant species to full eradication. Erodium moschatum (musk heron’s bill) remained the second most dominant species in oats (MC), whilst becoming the second most dominant species in the white mustard treatments and Weeds (CC). This species also became the most dominant species in Weeds, nematicide (CC) and Caliente (CC). Euphorbia peplus (stinging milkweed) was the most dominant species in Nemat (CC) and the second most dominant in oats (CC). This was also the first season in which the species was observed in all the treatments. 2011 Ryegrass remained the most dominant species in the MC treatments of canola, Caliente, Nemat and Weeds (Table 13). With the exception of white mustard, the same trend that occurred between the CC and MC treatments of a species during 2010 (Table 12), was once again observed during 2011 (Table 13).This supports the observation that chemical control during budbreak plays a major role in the suppression of ryegrass. During this season, ryegrass was controlled totally by oats (CC) and Nemat (CC). Similar to the previous two seasons, wild radish was the most dominant species in the two oats treatments (Tables 11 to 13). This weed became the most dominant species in the two canola treatments and Nemat (CC) (Table13). Musk heron’s bill remained the most dominant species in Weedsnem (CC) and the second most dominant species in oats (MC) and white mustard (CC). This weed became the most dominant species in Weeds (CC), and the second most dominant in oats (CC), canola (CC), Nemat (CC). It seems, therefore, as if a trend is developing where musk heron’s bill is starting to manifest its dominance in the CC treatments, with the exception of Caliente. Although yellow sorrel occurred in all the treatments, it did not dominate in any of the treatments (Table 13), which is in contrast




Table 11. The effect of soil cultivation practices on the spectrum of dominant winter growing weeds (species selected that were 10% or more of the total spectrum of weeds present in any year of the study), as measured during August 2009.

Treatment

Weed stand in g/0.5 m2

Raphanus

raphanistrum

Oxalis pes-

caprae

Erodium

moschatum

Vicia

species

Avena

fatua

Rapistrum

rigosum

Euphorbia

peplus

Lolium

species

Galinsoga

parviflora

Other

1. Avena sativa cv. Pallinup (oats), CC1 2.05 0.88 0 0.07 0 0 0 0.09 0 0.27 2. Oats, MC2 2.68 1.34 1.39 0.07 0 0 0 1.47 0 0.18 3. Sinapis alba cv. Braco (white mustard), CC 0 4.79 0.22 0.13 0.33 0.01 0 2.46 0 0.26 4. White mustard, MC 3.67 3.24 1.18 6.03 0 0.05 0 2.04 0 0.30 5. Brassica napus cv. AVJade (canola), CC 2.59 7.23 0 0.14 0.02 0 0.13 2.71 0 0.27 6. Canola, MC 0.02 7.81 0.18 0 0 0 0 10.72 0 0.19 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 5.31 0.07 0.01 0.22 0 0 2.91 0 0.12 8. Caliente, MC 0.19 6.33 0 20.75 0 0.34 0.20 3.65 0 0.21 9. Eruca sativa cv. Nemat (Nemat), CC 0 6.23 0 1.02 0 0 0 3.16 0 0.34 10. Nemat, MC 1.35 12.37 0.29 0 0 0 0 5.01 0 0.17 11. No cover crop (Weeds), CC 3.59 9.18 1.03 0 3.55 0 0 11.86 0 1.51 12. Weeds, MC 6.07 4.82 0 1.79 0 0 0 21.91 0 1.35 13. Weeds + nematicide (Weedsnem), CC 0.05 3.51 3.07 0.46 0 0 0.07 8.29 0 1.88 14. Weedsnem, MC 0.66 1.69 1.65 0 5.28 0 0.03 7.39 0 1.53 LSD(p≤0.05) 4.98

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine bud break, full surface chemical control from berry set.





Treatment


Raphanus

raphanistrum

Oxalis pes-

caprae

Erodium

moschatum

Vicia

species

Avena

fatua

Rapistrum

rigosum

Euphorbia

peplus

Lolium

species

Galinsoga

parviflora

Other

1. Avena sativa cv. Pallinup (oats), CC1 7.64 0.05 0.02 0.15 0 0 3.37 0.32 0 0.07 2. Oats, MC2 9.78 0.15 1.83 0.21 0 0 0.51 1.65 0 0.14 3. Sinapis alba cv. Braco (white mustard), CC 0.49 0 1.38 0.06 0 0 1.10 3.11 0 0.08 4. White mustard, MC 2.06 0.29 7.95 1.98 0 0 0.11 15.70 0 0.07 5. Brassica napus cv. AVJade (canola), CC 5.26 8.29 4.03 0 0 0 3.78 0.71 0 0.19 6. Canola, MC 6.09 3.87 0.15 0 0 0 1.53 24.24 0 0.06 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0.37 0.29 1.89 0.21 0 0 0.75 1.32 0 0.06 8. Caliente, MC 0.90 1.30 0.01 0.01 0 0 0.47 9.51 0 0.08 9. Eruca sativa cv. Nemat (Nemat), CC 1.20 0.15 0 0.13 0 0 1.28 0.03 0 0.04 10. Nemat, MC 1.71 1.13 0.62 0 0 0 0.38 18.63 0 0.04 11. No cover crop (Weeds), CC 22.55 1.13 16.74 1.65 1.24 0 5.33 7.64 0 0.39 12. Weeds, MC 10.82 3.15 4.23 0.11 18.28 0 1.82 43.73 0 0.37 13. Weeds + nematicide (Weedsnem), CC 19.31 2.26 26.71 4.46 1.69 0 9.59 9.23 0 0.48 14. Weedsnem, MC 16.57 1.79 4.87 0 15.08 0 0.87 30.24 0 0.20 LSD(p≤0.05) 4.20






Treatment


Raphanus

raphanistrum

Oxalis pes-

caprae

Erodium

moschatum

Vicia

species

Avena

fatua

Rapistrum

rigosum

Euphorbia

peplus

Lolium

species

Galinsoga

parviflora

Other

1. Avena sativa cv. Pallinup (oats), CC1 4.26 0.42 3.08 0 0.39 0 0.73 0 0 0.11 2. Oats, MC2 12.80 0.26 6.62 0 0 0 3.37 0.61 0 0.02 3. Sinapis alba cv. Braco (white mustard), CC 4.36 1.03 4.60 0 0 0 1.38 9.64 0 0.11 4. White mustard, MC 0.36 1.03 2.21 0.11 0.35 0 5.61 2.25 0 0.03 5. Brassica napus cv. AVJade (canola), CC 10.07 1.25 2.74 0 0 0.81 1.87 0.04 0 0.17 6. Canola, MC 40.64 1.22 2.72 0 0.94 0 3.35 31.93 0 0.06 7. Brassica juncea cv. Caliente 199 (Caliente), CC 3.53 0.51 0.96 0 0.02 0.02 2.86 4.33 0 0.09 8. Caliente, MC 3.38 3.12 2.51 1.09 0 1.47 5.36 24.92 0.15 0.13 9. Eruca sativa cv. Nemat (Nemat), CC 8.20 1.94 4.52 0.04 0 0 1.03 0 1.09 0.27 10. Nemat, MC 19.88 4.30 0 0 1.34 0 7.76 48.69 0 0.14 11. No cover crop (Weeds), CC 28.52 1.58 80.71 6.52 1.43 0 23.60 3.01 1.88 0.34 12. Weeds, MC 17.94 6.08 7.51 1.05 16.49 0.20 26.00 41.04 0 1.09 13. Weeds + nematicide (Weedsnem), CC 12.00 3.66 70.11 1.38 0 0 9.49 8.64 0 0.56 14. Weedsnem, MC 32.14 4.02 16.48 0 54.92 0.10 13.56 35.25 0 0.63 LSD(p≤0.05) 7.89





to the previous two seasons (Tables 11 and 12). Although stinging milkweed was once again present in all the treatments (Table 13), the species lost its dominance in Nemat (CC) and became dominant in white mustard (MC). However, as with the previous season, no definite trends could be detected. 2012 Musk heron’s bill became the dominant species all the treatments with the exception of canola (MC) in which it was the third most dominant species, as well as Nemat (MC) and Weedsnem (MC) in which it was the third most dominant species (Table 14). In the case of the oats treatments, it replaced wild radish which dominated during the previous three seasons (Tables 11 to 13). The dominance of ryegrass in most of the other treatments was, terminated by the application of a grass specific herbicide approximately two weeks after sowing the broadleaf cover crops (end of May) to control the young germinated ryegrass without harming the broadleaf cover crops (Table 14). This grass specific herbicide was also applied in the treatments in which no cover crop was sown, but not in the two oats treatments, the cover crop being a grass species as well. The chemical control of ryegrass during autumn, therefore, most probably facilitated the dominance of musk heron’s bill in all the treatments, with the exception of the two oats treatments. Stinging milkweed disappeared from all the cover crop treatments, with the exception of Nemat (MC). From 2010 onwards the stand of Avena fatua (wild oats) in Weeds (MC) and Weeds, nematicide (MC) was always higher than that of the other treatments, with the exception of Nemat (MC) (Tables 12 to 14). Wild oats dominated the weed spectrum in Weeds, nematicide since 2011 (Tables 12 and 13) and in Nemat (MC) during 2012 (Table 13), while it was the second most dominant species in Weeds (MC) during 2010 and 2012 (Tables 11 and 13). Rapistrum rigosum (wild mustard) dominated the weed spectrum in canola (MC), after being absent from this treatment during the previous three seasons (Tables 10 to 13). 2013 Musk heron’s bill remained the most or second most dominant species in all the treatments. (Table 15). It seems that the cover crops being established as late as 23 May during this season, prevented the ryegrass from regaining its dominance in any treatment. Ryegrass was totally eradicated from the oats treatments, white mustard (CC) and Nemat (CC). Wild radish dominated oats (MC), canola (MC and Nemat (MC), while wild oats remained dominant in Weedsnem (MC) (Table 15), as in the previous two seasons (Tables 13 and 14). Galinsoga parviflora (gallant soldier) appeared in both Nemat (CC) and Weeds (CC) for the first time during the 2011 season and remained in these treatments during 2012 and 2013 (Tables 11 to 15). This species was the third most dominant species in Nemat (CC) during 2011 and 2012 and became the most dominant species in 2013 (Tables 13 to 15). In the case of Weeds (CC), the species became the second most dominant during 2013 (Table 15). Effect of treatments on the composition of the summer weed population at grapevine berry set 2009 During this first season of application, either musk heron’s bill or ryegrass dominated the weed spectrum in all the treatments (Table 16). Wild radish was the only other species that were present in all the treatments. This species was the second most dominant weed in oats (MC), white mustard (CC), Weeds (MC) and the two Weedsnem treatments. The stand of wild radish exceeded the non-classified weeds (other) only in Weedsnem (MC). 2010 The stand of Musk heron’s bill was reduced from being either the dominant or second most dominant species in 2009 (Table 16), to total suppression in the two oats and two Caliente treatments, as well as white mustard (MC), canola (MC) Nemat (MC) and Weeds (CC) in the



2010/11 season (Table 17). This species, however, remained dominant in canola (CC) and was still the second most dominant species in Weeds (CC) (Table 17), despite the drastic reduction





Treatment


Raphanus

raphanistrum

Oxalis pes-

caprae

Erodium

moschatum

Vicia

species

Avena

fatua

Rapistrum

rigosum

Euphorbia

peplus

Lolium

species

Galinsoga

parviflora

Other

1. Avena sativa cv. Pallinup (oats), CC1 0.27 0.23 2.73 0 0 0 0 0.02 0.21 0.08 2. Oats, MC2 12.77 0.03 13.28 0 0.05 0.02 0 0.01 0 0.27 3. Sinapis alba cv. Braco (white mustard), CC 3.70 1.04 5.26 0 0 2.07 0 0.13 0 0.12 4. White mustard, MC 0 6.89 14.13 0 1.05 0.01 0 0.03 0.03 0.19 5. Brassica napus cv. AVJade (canola), CC 1.29 5.31 6.79 0 0 0.04 0 0 0 0.21 6. Canola, MC 0 10.21 8.00 0 0.21 11.50 0 5.32 0.18 0.13 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0.13 2.99 24.57 0 0 0 0 1.63 0 0.13 8. Caliente, MC 1.44 8.46 25.66 0 0 0 0 5.10 0 0.15 9. Eruca sativa cv. Nemat (Nemat), CC 0.43 2.65 8.71 0 0 0.08 0 0.05 1.54 0.13 10. Nemat, MC 1.68 6.64 10.34 0 26.86 0 7.28 3.77 0.13 0.23 11. No cover crop (Weeds), CC 12.04 7.71 122.52 0 0 7.34 6.00 0.88 1.22 0.36 12. Weeds, MC 9.51 4.36 53.95 0 28.75 4.91 2.84 19.96 0 0.30 13. Weeds + nematicide (Weedsnem), CC 1.56 14.57 92.83 0 4.56 6.00 2.43 1.70 0.18 0.53 14. Weedsnem, MC 15.49 9.57 19.28 0 66.87 2.85 1.51 10.67 0 0.29 LSD(p≤0.05) 7.11






Treatment


Raphanus

raphanistrum

Oxalis pes-

caprae

Erodium

moschatum

Vicia

species

Avena

fatua

Rapistrum

rigosum

Euphorbia

peplus

Lolium

species

Galinsoga

parviflora

Other

1. Avena sativa cv. Pallinup (oats), CC1 3.78 0 14.57 0 0 0 0 0 0 0.14 2. Oats, MC2 18.44 0.05 13.57 0 0 0.31 0 0 0 0.08 3. Sinapis alba cv. Braco (white mustard), CC 2.97 0.53 5.88 0 0 0 0.28 0 0.33 0.12 4. White mustard, MC 0.66 2.31 16.48 0 0 0.19 0.26 0.96 0.59 0.16 5. Brassica napus cv. AVJade (canola), CC 0.92 1.20 11.76 0 0.94 0 0 0.04 0.12 0.24 6. Canola, MC 28.83 2.58 3.23 0 0 0 0 1.96 3.12 0.21 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0.30 0.98 13.14 0 0.33 0 0 1.49 0 0.11 8. Caliente, MC 3.50 3.76 8.93 0 0 0.36 0.22 2.94 0 0.27 9. Eruca sativa cv. Nemat (Nemat), CC 5.38 0.29 7.46 0 0 0.81 0 0 16.25 0.17 10. Nemat, MC 16.10 1.89 7.70 0 0.28 0.20 0 2.19 5.74 0.15 11. No cover crop (Weeds), CC 0.12 7.26 76.93 0 20.58 0 0 1.33 21.55 0.42 12. Weeds, MC 1.28 6.17 34.95 0 25.79 0 0 4.95 0 0.54 13. Weeds + nematicide (Weedsnem), CC 0.67 7.56 81.31 0 5.24 0 0 3.90 0.63 0.41 14. Weedsnem, MC 0.54 6.45 18.61 0 60.69 0 0 3.86 0 0.26 LSD(p≤0.05) 6.04





Table 16. The effect of soil cultivation practices on the spectrum of dominant weeds growing from grapevine budbreak to berry set (species selected that were 15% or more of the total spectrum of weeds present in any year of the study), as measured end of November 2009.

Treatment


Tribulus

terrestris

Amaranthus

thunbergii

Digitaria

sanguinalis

Raphanus

raphanistrum

Erodium

moschatum

Lolium

species

Other

1. Avena sativa cv. Pallinup (oats), CC1 0 0 0 2.53 8.67 0.87 3.49 2. Oats, MC2 0 0 0.53 4.33 40.13 1.93 2.62 3. Sinapis alba cv. Braco (white mustard), CC 2.23 14.53 4.43 11.17 16.40 5.60 3.68 4. White mustard, MC 0.20 0 0 5.07 15.63 0.23 2.58 5. Brassica napus cv. AVJade (canola), CC 0 0 0 1.67 23.53 35.57 2.53 6. Canola, MC 0 0 0.60 0.63 36.70 49.93 2.05 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 1.53 0 1.80 10.37 9.47 2.39 8. Caliente, MC 0.23 0 2.43 3.97 9.87 12.30 3.15 9. Eruca sativa cv. Nemat (Nemat), CC 0 0 0.20 2.07 5.70 11.33 2.95 10. Nemat, MC 0.23 0 0 2.07 10.03 3.27 2.24 11. No cover crop (Weeds), CC 0 0 0 0.37 40.43 15.90 2.10 12. Weeds, MC 0.13 0 2.17 11.70 102.63 2.63 3.11 13. Weeds + nematicide (Weedsnem), CC 2.17 0 0 6.37 33.20 5.70 1.79 14. Weedsnem, MC 0 0 0 27.07 157.87 16.27 1.62 LSD(p≤0.05) 15.30






Treatment


Tribulus

terrestris

Amaranthus

thunbergii

Digitaria

sanguinalis

Raphanus

raphanistrum

Erodium

moschatum

Lolium

species

Other

1. Avena sativa cv. Pallinup (oats), CC1 0.60 3.67 0.43 4.90 0 0 0.25 2. Oats, MC2 1.37 0 0.93 66.10 0 0.83 0.66 3. Sinapis alba cv. Braco (white mustard), CC 0.50 0.37 0.30 0.90 0.20 0.13 0.23 4. White mustard, MC 2.40 2.07 0.07 2.83 0 21.43 0.50 5. Brassica napus cv. AVJade (canola), CC 0.17 0.10 0.57 0 1.57 0 0.27 6. Canola, MC 0.93 0 0.50 10.13 0 60.53 1.73 7. Brassica juncea cv. Caliente 199 (Caliente), CC 20.17 0 0.10 0 0 0 0.35 8. Caliente, MC 13.30 0 1.80 2.67 0 19.30 1.05 9. Eruca sativa cv. Nemat (Nemat), CC 1.33 0 0.47 3.00 0.27 0 0.33 10. Nemat, MC 1.63 0.13 0.47 8.37 0 42.67 0.62 11. No cover crop (Weeds), CC 1.07 0.63 0.40 7.90 1.73 0 0.83 12. Weeds, MC 0.27 0 0 13.53 0.10 10.27 1.66 13. Weeds + nematicide (Weedsnem), CC 0 0 0.30 5.17 0 0.17 0.87 14. Weedsnem, MC 0.07 0 0 9.00 0.63 23.93 1.18 LSD(p≤0.05) 6.94





in the stand of this weed in these two treatments from 2009 to 2010 (Tables 16 and 17). Ryegrass remained the dominant species in canola (MC), Caliente (MC) (Tables 16 and 17) and became the dominant species in white mustard MC, Nemat (MC) and Weedsnem (MC) (Table 17). This species was also the second most dominant species in Weeds (MC). A clear trend was, therefore, establishing, where the stand of ryegrass in the MC treatment of a species always exceeded that of the CC treatment of the same species. With the exception of Pallinup oats, this difference was significant. Ryegrass was suppressed totally from grapevine budbreak to berry set by all the CC treatments, with the exception of white mustard (CC) and Weedsnem (CC). This management practice can, therefore, play an important role in the control of this problem weed. Wild radish remained the second most dominant weed in white mustard (MC) and Weedsnem (MC) (Tables 16 and 17). This species also filled the niche left by musk heron’s bill and to a lesser extent ryegrass, by dominating the weed spectrum in the oats and Weeds treatments, as well as white mustard (CC), Nemat (CC) and Weedsnem (CC) (Table 16). Although Tribulus terrestris (common dubbeltjie) and Digitaria sanguinalis (crab fingergrass) infested most of the treatments during 2010, common dubbeltjie was the most aggressive, dominating Caliente (CC) within a season (Tables 16 and 17). Common dubbeltjie also became the second most dominant species in oats (MC), white mustard (CC) and Caliente (MC) (Table 17). 2011 With the exception of oats (MC). Musk heron’s bill was suppressed totally in all the treatments during 2011 (Table 18). Ryegrass was totally suppressed from grapevine budbreak to berry set by all the CC treatments. The stand of this species was also reduced in all the MC treatments compared to the stand observed in the previous season (Tables 17 and 18) However, ryegrass remained the dominant species in white mustard (MC) and Nemat (MC) (Table 18). This species was also the second most dominant species in canola (MC), Weeds (MC) and Weedsnem (MC). The clear trend that occurred during 2010, was once again observed, even though it was only significant for Nemat (Tables 17 and 18). This confirmed that CC can play an important role in the control of this problem weed. Wild radish remained dominant in oats (MC), Weeds (MC) and Weedsnem (CC), white mustard (MC) and Weedsnem (MC) (Tables 17 and 18). Wild radish also became dominant in canola (MC), Caliente (MC), and Weedsnem (MC) (Table 18). However, this species was totally suppressed in white mustard (CC), for the second consecutive season, and Nemat (CC), with crab fingergrass becoming dominant in these treatments (Tables 17 and 18). In contrast to the previous season, crab fingergrass also dominated the weed spectrum in canola (CC), Caliente (CC) and Weeds (CC) (Tables 17 and 18). It seems that the application of CC during budbreak facilitated the dominance of crab fingergrass during grapevine berry set. No definite trend was observed for common dubbletjie. This weed, however, became dominant in oats (CC) and was the second most dominant species in oats (MC), canola (CC), the two Caliente treatments and Weeds (CC) (Table 18). 2012 Musk heron’s bill regained dominance in Weedsnem (CC) (Table 19). Ryegrass was suppressed totally for the third consecutive season in oats (CC), Caliente (CC) and Nemat (CC), as well as for the second consecutive season in oats (MC) and Weedsnem (CC) (Tables 17 to 19). Although total control could not be achieved with white mustard (CC) and canola (CC), the ryegrass stand was significantly lower than that of the corresponding MC treatment. The trend that occurred during 2010 and 2011, was once again observed for the third consecutive season (Tables 17 to 19). It can, therefore, be accepted that CC plays an important role in the control of this problem weed. Wild radish remained dominant in Weeds (MC) and Weedsnem (MC) (Tables 18 and 19). This species also remained the second most dominant in oats (MC) and Nemat (MC). Wild radish was, however, totally suppressed in all the CC treatments (Table 19), it being the third consecutive



season in canola (CC) and the second consecutive season in white mustard (CC) and Nemat (CC) (Tables 17 to 19). Total suppression of this species was also achieved with white mustard (MC) (Table 19). The dominance of crab fingergrass first observed in the CC treatments of white mustard, canola, Caliente and Nemat at the end of November 2011 (grapevine berry set), was also observed at the end of November 2012 (Tables 18 and 19). This species also dominated oats (MC) for the first time and was the second most dominant species in white mustard (MC), the Weeds treatments and Weedsnem (MC). Effect of treatments on the composition of the summer weed population during the grapevine post-harvest period before seedbed preparation took place (early April). 2009 During this pre-treatment measurement at the end of summer (post-harvest), Rhynchelytrum repens (Natal red-top), a perennial grass, was the most dominant species in all the treatments except Nemat (MC), in which it was absent (Table 20). The Conyza species (flax-leaf fleabane), problem broadleaf annuals, were present in all the treatments and were the second most dominant in white mustard (CC), the two canola treatments, Caliente (MC), Nemat (MC), Weeds (CC) and Weedsnem (MC). With the exception of canola (CC), common dubbeltjie was also found in all the treatments and observed to be the dominant species in Nemat (MC) and the second most dominant in oats (CC) and Caliente (CC). Cynodon dactylon (common couch), a perennial grass generally observed to be one of the problem weeds in the vineyards of South Africa, was present in all the treatments, except the two Nemat treatments. Common couch was found to be the second most dominant species in white mustard (MC) and Weedsnem (CC). Crab fingergrass was the second most dominant species in oats (MC) and Nemat (CC), but absent from canola (MC), Weeds (MC) and the Weedsnem treatments. Although Polygonum aviculare (prostrate knotweed) did not dominate any treatment, it was present in all the treatments, with the exception of Caliente (CC), Weeds (MC) and Weedsnem (CC). Boerhavi erecta (erect Boerhavia) was found in nine of the fourteen treatments and was the second most dominant species in Weeds (MC).

The high values of the other species is an indication that a lot of species was found in these treatments that did not exceed the criteria of 22% or more of the total weed stand in any of the treatments during the study. The average total DMP of the weed stand before the trial started was 5.53 t/ha, which is very high, taking into account that the vineyard was drip irrigated and it being the end of summer. 2010 At the end of the first season during which the different treatments were applied, Natal red-top lost its dominance in all the treatments, except Weedsnem (CC) (Tables 20 and 21). It appeared in Nemat (MC) for the first time and was totally controlled in white mustard (MC) (Table. 21). Flax-leaf fleabane, a problem broadleaf annual, became the dominant species in the CC treatments of oats, white mustard, canola and Nemat, whilst becoming the second most dominant species in oats (MC), white mustard (MC) and Caliente (CC). This species also remained the second most dominant species in Caliente (MC) and Nemat (MC). Common dubbeltjie was absent in canola (CC) for the second consecutive season and disappeared from Nemat (MC), where it was the most dominant species (Tables 20 and 21). However, this species became the most dominant in Weeds (CC) and Weedsnem (MC) (Table 21). Common couch became the dominant species in white mustard (MC) and the two Caliente treatments, while becoming the second most dominant species in the two canola treatments. The species disappeared from white mustard (CC), Nemat (MC) and Weedsnem (CC). Crab fingergrass was observed in all the treatments, except Weeds (CC) and became dominant in the MC treatments of canola, Nemat and Weeds. In Weeds (MC), the stand of crab fingergrass was higher than that of the other weeds (Table 21), its dominance realising from a total absence during the previous season (Table 20). Crab fingergrass became the second most dominant species in white mustard (CC) (Table 21). Prostrate knotweed disappeared from all the treatments, except





Treatment


Tribulus

terrestris

Amaranthus

thunbergii

Digitaria

sanguinalis

Raphanus

raphanistrum

Erodium

moschatum

Lolium

species

Other

1. Avena sativa cv. Pallinup (oats), CC1 1.49 0 0 0.42 0 0 0.04 2. Oats, MC2 1.30 0 0.15 52.55 0.43 0 0.26 3. Sinapis alba cv. Braco (white mustard), CC 0.48 0 7.01 0 0 0 0.17 4. White mustard, MC 0.19 0 0 0.49 0 2.77 0.05 5. Brassica napus cv. AVJade (canola), CC 0.20 0 1.91 0 0 0 0.02 6. Canola, MC 0 0 0.13 7.82 0 4.01 0.41 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0.69 0 2.57 0.26 0 0 0.03 8. Caliente, MC 2.70 0 0 6.35 0 2.27 0.38 9. Eruca sativa cv. Nemat (Nemat), CC 0.10 0 15.04 0 0 0 0.18 10. Nemat, MC 0 0 1.57 3.81 0 5.75 0.30 11. No cover crop (Weeds), CC 0.07 0 0.49 0.05 0 0 0.06 12. Weeds, MC 0 0 0 44.28 0 3.59 1.10 13. Weeds + nematicide (Weedsnem), CC 0 0 0 0.29 0 0 0.28 14. Weedsnem, MC 0 0 0 16.66 0 3.67 1.41 LSD(p≤0.05) 5.26






Treatment


Tribulus

terrestris

Amaranthus

thunbergii

Digitaria

sanguinalis

Raphanus

raphanistrum

Erodium

moschatum

Lolium

species

Other

1. Avena sativa cv. Pallinup (oats), CC1 0 2.43 0 0 0 0 0.05 2. Oats, MC2 0 0.02 11.39 0.38 0.03 0 0.08 3. Sinapis alba cv. Braco (white mustard), CC 0.29 0 31.53 0 0 0.89 0.19 4. White mustard, MC 0 1.49 9.44 0 1.08 10.26 0.36 5. Brassica napus cv. AVJade (canola), CC 0 0.39 2.15 0 0 0.61 0.08 6. Canola, MC 10.55 0 7.88 4.67 0 43.59 0.54 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 0.81 7.63 0 0.86 0 0.11 8. Caliente, MC 3.48 0 28.04 6.14 0.79 10.36 0.60 9. Eruca sativa cv. Nemat (Nemat), CC 0.45 0 39.16 0 0 0 0.12 10. Nemat, MC 0 0 8.25 11.41 0 65.83 0.29 11. No cover crop (Weeds), CC 0 0 1.53 0 0 1.59 0.13 12. Weeds, MC 0 0 3.15 20.30 2.31 2.52 0.76 13. Weeds + nematicide (Weedsnem), CC 0 0 0 0 5.38 0 0.29 14. Weedsnem, MC 0 0 3.52 26.05 2.50 0 0.35 LSD(p≤0.05) 4.97





Table 20. The effect of soil cultivation practices on the spectrum of dominant weeds present in the vineyard just before seedbed preparation (species selected that were 22% or more of the total spectrum of weeds present in any year of the study), as measured early April 2009, before the treatments were applied.

Treatment


Conyza

bonariensis

Tribulus

terrestris

Digitaria

sanguinalis

Rhynchelytrum

repens

Cynodon

dactylon

Polygonum

aviculare

Boerhavia

erecta

Anagallis

arvensis

Other

1. Avena sativa cv. Pallinup (oats), CC1 5.60 16.93 7.07 85.63 0.10 0.93 0 0 155.94 2. Oats, MC2 2.80 2.97 15.43 37.50 21.03 3.20 1.67 0 260.30 3. Sinapis alba cv. Braco (white mustard), CC 15.20 4.27 13.90 17.07 9.23 4.97 0.03 0 203.90 4. White mustard, MC 7.00 0.30 7.63 50.54 12.77 1.73 1.60 0 295.60 5. Brassica napus cv. AVJade (canola), CC 16.20 0 14.47 96.03 1.77 0.03 0 0 161.57 6. Canola, MC 47.43 5.27 0 66.23 5.33 2.27 1.07 0 200.10 7. Brassica juncea cv. Caliente 199 (Caliente), CC 14.60 50.10 9.97 96.97 5.90 0 0.03 0 106.80 8. Caliente, MC 18.97 0.83 6.57 66.17 12.20 2.37 0 0 105.03 9. Eruca sativa cv. Nemat (Nemat), CC 2.60 8.40 28.00 102.60 0 2.33 0 0 64.03 10. Nemat, MC 4.80 21.70 2.73 0 0 2.67 0.93 0 122.73 11. No cover crop (Weeds), CC 13.93 7.87 3.07 109.43 7.40 2.07 0 0 127.80 12. Weeds, MC 0.73 4.20 0 194.57 4.47 0 5.97 0 83.13 13. Weeds + nematicide (Weedsnem), CC 0.43 1.90 0 147.33 5.33 0 2.50 0 143.97 14. Weedsnem, MC 13.10 0.10 0 103.27 0.30 6.70 1.47 0 187.67 LSD(p≤0.05) 79.48





Table 21. The effect of soil cultivation practices on the spectrum of dominant weeds growing from grapevine berry set to just before seedbed preparation (species selected that were 22% or more of the total spectrum of weeds present in any year of the study), as measured early April 2010.

Treatment


Conyza

bonariensis

Tribulus

terrestris

Digitaria

sanguinalis

Rhynchelytrum

repens

Cynodon

dactylon

Polygonum

aviculare

Boerhavia

erecta

Anagallis

arvensis

Other

1. Avena sativa cv. Pallinup (oats), CC1 9.13 1.97 0.37 0.17 0.10 0.03 0.23 0 9.30 2. Oats, MC2 3.87 1.73 3.30 2.07 2.23 0 20.10 0 17.97 3. Sinapis alba cv. Braco (white mustard), CC 7.73 0.03 1.73 0.60 0 0 0.03 0 5.00 4. White mustard, MC 2.63 0.23 0.73 0 11.37 0 0.50 0 3.47 5. Brassica napus cv. AVJade (canola), CC 7.00 0 0.03 2.63 5.33 0 3.40 0 5.20 6. Canola, MC 2.07 0.07 10.00 7.77 8.47 0 0.53 0 1.30 7. Brassica juncea cv. Caliente 199 (Caliente), CC 8.50 0.13 0.20 6.67 16.07 0.43 0.13 0 1.70 8. Caliente, MC 5.87 0.73 0.97 2.67 11.23 0 0 0 2.80 9. Eruca sativa cv. Nemat (Nemat), CC 11.30 2.47 1.67 0.60 0.03 0 0 0 2.00 10. Nemat, MC 4.00 0 7.67 1.33 0 0 0.13 0 3.87 11. No cover crop (Weeds), CC 0.03 5.53 0 3.83 3.23 0 1.10 0 4.87 12. Weeds, MC 0.30 2.13 22.27 7.60 4.20 0 0.80 0 6.97 13. Weeds + nematicide (Weedsnem), CC 0.43 0.87 0.03 2.97 0 0 0.47 0 6.30 14. Weedsnem, MC 0 18.70 4.13 1.47 1.97 0 4.53 0 11.97 LSD(p≤0.05) 11.75





the CC treatments of oats and Caliente. Erect Boerhavia was observed in all the treatments, except Caliente (MC) and Nemat (CC), and was the second most dominant species in Weeds (MC). Erect Boerhavia became the dominant species in oats (CC), with its stand being higher than that of all the other weeds.

The average total DMP of the weed stand measured post-harvest was 0.53 t/ha, which is only 9.58% of the weed stand measured post-harvest during 2009 (5.53 t/ha). This clearly illustrates the benefit of the weed control applied just before budbreak and during grapevine berry set. 2011 Although Natal red-top was present in all the treatments, the species did not dominate in any of the treatments (Table 22). Flax-leaf fleabane remained the dominant species in oats (CC) and became the most dominant species in oats (MC) (Tables 21 and 22). It also remained the second most dominant species in Caliente (MC), and was observed to be the second most dominant in canola (MC), Nemat (CC) and Weeds (MC) as well. Common dubbeltjie remained the most dominant species in Weeds (CC). This species, however, remained absent from Nemat (MC) and disappeared from canola (MC), Caliente (CC) and Weedsnem (MC). Common couch disappeared from the nine treatments in which it was observed during April 2010, causing the species to be absent from the trial during this period. Although crab fingergrass remained absent in Weeds (CC) and disappeared from Weedsnem (CC) (Tables 21 and 22), it dominated the two treatments of white mustard, Caliente and Nemat, as well as the MC treatments of canola, Weeds and Weedsnem (Table 22). All the MC treatments were dominated by crab fingergrass, with the exception of oats (MC), in which it was the second most dominant species (Table 22). Prostrate knotweed disappeared from the two treatments in which it was observed during April 2010, causing the species to be absent from the trial during this period. Although erect Boerhavia was the second most dominant species in Weeds (CC) and Weedsnem (CC), it was not observed in oats (CC), white mustard (CC), canola (CC), the two Caliente treatments and Nemat (CC) (Table 22). This is an indication that the mulch of the cover crops used in the trial did help to suppress this species effectively. Anagallis arvensis (pimpernel) appeared in all the treatments for the first time and dominated canola (CC) and Weedsnem (CC) within one season. The species also became the second most dominant species in white mustard (MC), Caliente (CC), Nemat (CC) and Weedsnem (MC).

The average total DMP of the weed stand measured post-harvest was 0.83 t/ha, which is approximately the same as that measured during 2010 (0.53 t/ha) and only 15% of the weed stand measured post-harvest during 2009 (5.53 t/ha). This confirms the benefit of the weed control applied just before budbreak and during grapevine berry set. 2012 Natal red-top dominated oats (MC), but disappeared from the white mustard treatments, canola (CC), Weeds (CC) and Weedsnem (CC) (Table 23). In contrast to the previous season, flax-leaf fleabane did not dominate any of the treatments (Tables 22 and 23). This species remained absent in canola (CC) and disappeared from the oats and white mustard treatments, as well as canola (MC) and Nemat (MC). Common dubbeltjie remained the most dominant species in Weeds (CC) for the third consecutive season (Tables 21, 22 and 23), started to dominate oats (CC) and canola (MC), as well as became the second most dominant species in white mustard (MC). This species remained absent from Caliente (CC) and disappeared from white mustard (CC) (Tables 22 and 23). In contrast to the previous season common couch re-appeared and dominated the Caliente treatments, Nemat (MC), Weeds (MC) and the Weedsnem treatments. However, it remained fully suppressed in the oats treatments and Weeds (CC). Crab fingergrass remained absent in Weeds (CC) for the third consecutive season (Tables 21, 22 and 23) and in Weedsnem (CC) for the second consecutive season (Tables 22 and 23). This species remained dominant in



the two white mustard treatments and Nemat (CC) (Tables 22 and 23), while becoming dominant in canola (CC) (Table 23). Crab fingergrass was also the




Table 22. The effect of soil cultivation practices on the spectrum of dominant weeds growing from grapevine berry set to just before seedbed preparation (species selected that were 22% or more of the total spectrum of weeds present in any year of the study), as measured early April 2011.

Treatment


Conyza

bonariensis

Tribulus

terrestris

Digitaria

sanguinalis

Rhynchelytrum

repens

Cynodon

dactylon

Polygonum

aviculare

Boerhavia

erecta

Anagallis

arvensis

Other

1. Avena sativa cv. Pallinup (oats), CC1 1.27 0.57 0.03 0.19 0 0 0 0.67 0.35 2. Oats, MC2 16.13 0.13 12.96 0.15 0 0 0.17 1.56 5.64 3. Sinapis alba cv. Braco (white mustard), CC 2.77 0.10 24.15 2.94 0 0 0 0.67 0.13 4. White mustard, MC 0.13 3.31 11.26 2.65 0 0 0.28 9.41 2.31 5. Brassica napus cv. AVJade (canola), CC 0 0.23 0.09 0.33 0 0 0 9.20 0.90 6. Canola, MC 21.67 0 37.79 6.17 0 0 7.63 3.04 1.30 7. Brassica juncea cv. Caliente 199 (Caliente), CC 2.93 0 54.89 2.84 0 0 0 8.07 7.43 8. Caliente, MC 7.37 0.07 20.18 1.68 0 0 0 5.20 3.37 9. Eruca sativa cv. Nemat (Nemat), CC 12.23 0.03 25.09 1.73 0 0 0 5.93 0.07 10. Nemat, MC 1.17 0 10.20 0.30 0 0 5.46 9.20 0.94 11.No cover crop (Weeds), CC 12.30 36.43 0 0.37 0 0 18.79 6.17 0.20 12. Weeds, MC 10.78 0.03 49.69 10.23 0 0 0.15 1.85 4.67 13. Weeds + nematicide (Weedsnem), CC 0.17 1.23 0 0.27 0 0 3.06 6.80 1.19 14. Weedsnem, MC 3.41 0 21.81 0.32 0 0 0.13 10.94 3.16 LSD(p≤0.05) 21.39





Table 23. The effect of soil cultivation practices on the spectrum of dominant weeds growing from grapevine berry set to just before seedbed preparation(species selected that were 22% or more of the total spectrum of weeds present in any year of the study), as measured early April 2012.

Treatment


Conyza

bonariensis

Tribulus

terrestris

Digitaria

sanguinalis

Rhynchelytrum

repens

Cynodon

dactylon

Polygonum

aviculare

Boerhavia

erecta

Anagallis

arvensis

Other

1. Avena sativa cv. Pallinup (oats), CC1 0 19.78 9.36 0.39 0 1.10 0 0 5.10 2. Oats, MC2 0 3.50 13.98 14.34 0 0.44 0 0 137.90 3. Sinapis alba cv. Braco (white mustard), CC 0 0 91.32 0 1.05 1.89 0 0 7.94 4. White mustard, MC 0 14.20 41.74 0 1.02 8.22 0 0 12.94 5. Brassica napus cv. AVJade (canola), CC 0 20.98 47.61 0 45.29 0 0 0 6.65 6. Canola, MC 0 15.19 5.72 1.10 1.52 0 0 0 8.07 7. Brassica juncea cv. Caliente 199 (Caliente), CC 2.92 0 12.15 4.97 17.16 16.66 0 0 4.99 8. Caliente, MC 0.88 0.34 27.49 0.88 38.59 0 0 0 52.81 9. Eruca sativa cv. Nemat (Nemat), CC 0.42 1.15 39.05 4.65 13.60 2.66 0 0 21.28 10. Nemat, MC 0 1.53 10.07 1.27 57.23 0.36 0 0 7.16 11. No cover crop (Weeds), CC 0.33 41.36 0 0.90 0 0 0 0 33.31 12. Weeds, MC 1.97 1.10 12.62 0 42.18 2.45 0 0 19.84 13. Weeds + nematicide (Weedsnem), CC 0.36 0.53 0 6.69 41.61 1.00 0 0 39.42 14. Weedsnem, MC 5.58 1.77 1.97 0 41.40 0 0 0 39.96 LSD(p≤0.05) 34.42





second most dominant species in the two oats treatments, Caliente (MC), Nemat (MC) and Weeds (MC) (Table 23). Although the trend was not as clear as during the 2011 season, it seemed that it was easier for crab fingergrass to establish itself in the MC treatments (Tables 22 and 23). Prostrate knotweed re-appeared in the oats, white mustard and Nemat treatments, as well as in Caliente (CC) Weeds (MC) and Weedsnem (CC) (Table 23). With the exception of being the second most dominant species in Caliente (CC), prostrate knotweed did not dominate any of the treatments in which it re-appeared. Both erect Boerhavia and pimpernel were not observed in any of the treatments.

The average total DMP of the weed stand measured post-harvest was 1.74 t/ha, which is approximately double the stand of 0.83 t/ha measured during 2011. The observed increase is attributed to the summer rainfall being higher during the 2011/12 season than during the 2010/11 season (Table 24). This is an indication that weed control in the period from berry set to post-harvest should be considered, especially if the summer rainfall is relatively high. Table 24. The rainfall during the cover crop growing season (April to August), 0-60 days after the management practices were applied just before grapevine budbreak (September and October) and late summer/early autumn (November to March).

Treatment phase Seasonal rainfall (mm)

2009/10 2010/11 2011/12 2012/13 2013/14 April to August 456 414 404 595 642 September to October 171 77 80 231 151 November to March 163 97 152 120* Not applicable Total 790 588 636 946* Not applicable

*Does not include the rainfall from 19 to 31 March 2013 Natal red-top was observed in all the treatments, with the exception of oats (CC), but the species did not dominate in any of the treatments (Table 25). This was similar to the trend observed during 2011 (Table 22). As during the pre-treatment period (April 2009), flax-leaf fleabane was present in all the treatments during this season, but did not dominate any of them (Table 24). Common dubbeltjie was observed in all the treatments for the first time and dominated the most treatments since the inception of the trial (Tables 20 to 23 and 25). This species dominated the oats, canola and Caliente treatments, as well as Weeds (CC) (Table 25), while remaining the second most dominant species in white mustard (MC) (Tables 23 and 25). In contrast to the previous seasons, crab fingergrass was present in all the treatments (Tables 20 to 23 and 25). This species remained dominant for the third consecutive season in white mustard (CC) and Nemat (CC), as well as one of the two most dominant species in Nemat (MC) for the third consecutive season (Tables 22, 23 and 25). Crab fingergrass was also the second most dominant species in canola (CC) and Caliente (CC) (Table 25). However, the trend observed during April 2011 and 2012 did not manifest in April 2013 (Tables 22, 23 and 25). Although common couch was observed in all the treatments except oats (CC), the species lost its dominance in the CC treatments of canola, Caliente and Weedsnem (Tables 23 and 25). However, the species did become one of the two most dominant species in Nemat (CC), remained dominant in Weeds (MC) and Weedsnem (MC) and remained one of the two most dominant species in Caliente (MC). A trend was observed where common couch seemed to establish itself better during late summer where mechanical cultivation was applied during budbreak (MC), thereby leaving the soil mulch free during the summer. Prostrate knotweed disappeared from oats (CC) and Weedsnem (CC) and remained



absent from Weeds (CC). This species, however, started to dominate white mustard (MC) and Nemat (MC), and became the




Table 25. The effect of soil cultivation practices on the spectrum of dominant weeds growing from grapevine berry set to just before seedbed preparation(species selected that were 22% or more of the total spectrum of weeds present in any year of the study), as measured early April 2013.

Treatment


Conyza

bonariensis

Tribulus

terrestris

Digitaria

sanguinalis

Rhynchelytrum

repens

Cynodon

dactylon

Polygonum

aviculare

Boerhavia

erecta

Anagallis

arvensis

Other

1. Avena sativa cv. Pallinup (oats), CC1 2.68 19.46 3.93 0 0 0 0 0 26.55 2. Oats, MC2 3.32 33.38 16.05 0.14 13.71 23.16 0 0 21.97 3. Sinapis alba cv. Braco (white mustard), CC 3.11 2.02 19.38 1.78 2.51 10.63 0 0 25.31 4. White mustard, MC 4.69 23.09 4.55 0.82 5.40 53.72 0 0 33.66 5. Brassica napus cv. AVJade (canola), CC 0.86 22.58 10.60 4.08 1.52 1.16 0 0 34.66 6. Canola, MC 8.48 19.91 2.65 0.27 18.81 12.05 0 0 23.22 7. Brassica juncea cv. Caliente 199 (Caliente), CC 6.30 44.35 21.52 2.30 1.13 0.53 0 0 11.08 8. Caliente, MC 5.91 47.78 11.04 0.69 27.34 17.24 0 0 11.91 9. Eruca sativa cv. Nemat (Nemat), CC 6.64 5.27 28.78 1.28 8.32 2.06 0 0 29.87 10. Nemat, MC 10.29 3.78 18.80 11.28 4.66 25.53 0 0 10.33 11. No cover crop (Weeds), CC 1.20 21.59 6.30 3.19 14.45 0 0 0 19.96 12. Weeds, MC 8.25 0.27 7.69 7.91 102.52 0.32 0 0 13.65 13. Weeds + nematicide (Weedsnem), CC 7.99 12.80 3.13 1.95 4.11 0 0 0 27.89 14. Weedsnem, MC 2.99 6.33 6.14 7.86 71.38 4.60 0 0 20.67 LSD(p≤0.05) 27.03


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second most dominant species in ats (MC) and white mustard (CC) (Table 25). As in the case of

common couch, a trend was observed where prostrate knotweed seemed to establish itself better

during late summer where MC was applied. As observed during the 2012 season, both erect

Boerhavia and pimpernel were not observed in any of the treatments (Tables 23 and 25).

The average total DMP of the weed stand measured post-harvest was 1.82 t/ha,

which is again approximately double the stand of 0.83 t/ha measured during 2011. The observed

increase is once again attributed to the summer rainfall being higher during the 2012/13 season

than during the 2010/11 season (Table 24). This confrms that weed control in the period from

berry set to post-harvest should be considered, especially if the summer rainfall is relatively high.

It seems that the relatively low summer rainfall during the 2010/11 season compared to

that of the 2009/10, 2011/12 and 2012/13 seasons (Table 24), allowed pimpernel to appear in

April 2011 and dominate some of the treatments (Table 22). This coincided with the

disappearance of common couch and prostrate knotweed, who did not cope well with the dryer

summer. The relatively high summer rainfall during the 2011/12 and 2012/13 seasons (Table 24),

seemed to allow these two perennials to recover and dominate in some of the treatments (Tables

23 and 25)

Soil pathogen status Cylindrocarpon spp., the causal organism of black foot disease, was the most frequently isolated

grapevine pathogen (Table 26). It occurred in each of the 14 treatments 6 to 12 times during the

14 sampling periods. Severity in most of the treatments fluctuated slightly throughout the four

seasons or remained more or less the same. It is interesting to note that Weedsnem (MC) caused

a notable increase in the severity of Cylindrocarpon spp. infections during the 2011 season after

no or low severity levels were recorded during the two previous seasons. However, during the

fourth year these levels returned to the same levels detected during the first two seasons. The

only other notable increases in severity during the four seasons were caused by Weeds (CC) that

caused an increase in the May 2012 sampling period, and white mustard (MC) that caused an

increase at the end of 2010. However, in both these treatments severity levels returned to the

same level as detected at the beginning of the trial. In conclusion, none of the 14 treatments

caused a significant increase or reduction in Cylindrocarpon spp. infections after being subjected

to these treatments for four years if compared to the severity levels detected in each treatment at

the beginning of the trial in 2009. Phaeomoniella chlamydospora (Petri Disease) was the second most frequently isolated

pathogen (Table 27). It occurred in each of the 14 treatments 4 to 11 times during the 14 sampling

periods. The same fluctuating effect was observed as described above. Oats (MC), canola (CC),

the two Caliente treatments, Weeds (MC) and Weedsnem (CC) caused significant increases in

Phaeomoniella chlamydospora severity levels at various stages during the four years, but in all

cases severity levels returned to levels detected at the beginning of the trial in 2009. This indicated

that none of the treatments caused a significant increase or decrease in Phaeomoniella chlamydospora after being subjected to these treatments for four years compared to the severity

levels detected in each treatment at the beginning of the trial in 2009.

Phaeoacremonium spp. (Petri Disease) occurred at least once in each of the 14

treatments during the 14 sampling periods, except in Nemat (MC), where it was not detected at

all (Table 28). The two canola treatments and Weeds (MC) caused a significant increase in

Phaeoacremonium spp. severity in May 2011, December 2009 and August 2009, respectively,

but these levels decreased again to the same (low or zero) levels as detected at the beginning of

the trial in 2009. None of the treatments, therefore, caused a significant increase or decrease in

Phaeoacremonium spp. after being subjected to these treatments for four years compared to the

severity levels detected in each treatment at the beginning of the trial in 2009.


This document is confidential and any unauthorised disclosure is prohibited

Version 2015

Pythium spp., the cause of root rot was only detected in canola (MC), Nemat (CC) and

Weedsnem (CC), although at very low severity levels (Table 29). These levels also decreased

again to zero at the end of the fourth year of the trial. None of the treatments therefore caused a




Table 26. Severity (%) of Cylindrocarpon spp. isolated from the roots of grapevines subjected to cover crops, selected for their potential to bio-fumigate the soil, managed according to two cover crop management practices.

Treatment number1

Isolation Date

6 May

2009

20 Aug

2009

1 Dec

2009

21 Apr

2010

3 Aug

2010

7 Dec

2010

16 May

2011

23 Aug

2011

30 Nov

2011

8 May

2012

3 Sep

2012

26 Nov

2012

1. Avena sativa cv. Pallinup (oats), CC1 4.2 6.3 0 14.6 0 2.1 14.6 0 2.1 4.2 0 12.5 2. Oats, MC2 6.3 0 2.1 10.4 0 0 0 0 0 0 2.1 4.2 3. Sinapis alba cv. Braco (white mustard), CC 6.3 0 4.2 18.8 0 4.2 8.3 2.1 0 12.5 2.1 8.3 4. White mustard, MC 4.2 10.4 6.3 0 2.1 22.9 4.2 6.3 4.2 0 14.6 14.6 5. Brassica napus cv. AVJade (canola), CC 12.5 0 0 0 6.3 10.4 6.3 0 12.5 0 4.2 0 6. Canola, MC 8.3 18.8 4.2 0 6.3 4.2 8.3 4.2 18.8 4.2 0 20.8 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 2.1 0 0 0 0 6.3 0 8.3 6.3 4.2 4.2 8. Caliente, MC 8.3 12.5 4.2 0 0 0 18.8 6.3 14.6 2.1 0 2.1 9. Eruca sativa cv. Nemat (Nemat), CC 6.3 4.2 18.8 4.2 2.1 0 12.5 6.3 8.3 10.4 6.3 6.3 10. Nemat, MC 0 6.3 8.3 8.3 12.5 4.2 4.2 4.2 10.4 0 4.2 4.2 11. No cover crop (Weeds), CC 0 0 0 0 2.1 4.2 2.1 0 8.3 16.7 4.2 8.3 12. Weeds, MC 4.2 2.1 2.1 0 16.7 0 0 0 12.5 4.2 6.3 2.1 13. Weeds + nematicide (Weedsnem), CC 16.7 2.1 2.1 2.1 2.1 4.2 4.2 4.2 2.1 4.2 2.1 4.2 14. Weedsnem, MC 0 0 0 2.1 0 0 12.5 10.4 18.8 0 2.1 0 LSD(p≤0.05) 16.0

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row from grapevine bud break, full surface chemical control from berry set..




Table 27. Severity (%) of Phaeomoniella chlamydospora isolated from the roots of grapevines subjected to cover crops, selected for their potential to bio-fumigate the soil, managed according to two cover crop management practices.

Treatment Isolation Date

6 May 2009

20 Aug. 2009

1 Dec. 2009

21 Apr. 2010

3 Aug. 2010

7 Dec. 2010

16 May 2011

23 Aug. 2011

30 Nov. 2011

8 May 2012

3 Sep. 2012

26 Nov. 2012

1. Avena sativa cv. Pallinup (oats), CC1 0 2.1 0 0 0 0 0 8.3 2.1 0 12.5 2.1 2. Oats, MC2 0 4.2 0 10.4 2.1 0 0 0 18.8 12.5 20.8 0 3. Sinapis alba cv. Braco (white mustard), CC 0 2.1 2.1 0 0 8.3 4.2 4.2 0 0 0 10.4 4. White mustard, MC 8.3 0 2.1 10.4 4.2 2.1 6.3 2.1 8.3 12.5 2.1 6.3 5. Brassica napus cv. AVJade (canola), CC 0 2.1 0 37.5 0 2.1 0 4.2 0 4.2 8.3 2.1 6. Canola, MC 0 4.2 4.2 0 0 0 2.1 0 10.4 12.5 6.3 6.3 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 0 0 0 0 2.1 20.8 0 18.8 12.5 14.6 8.3 8. Caliente, MC 0 2.1 0 0 0 0 14.6 0 14.6 0 4.2 0 9. Eruca sativa cv. Nemat (Nemat), CC 16.7 0 0 14.6 6.3 0 2.1 0 4.2 0 25.0 33.3 10. Nemat, MC 0 12.5 0 0 0 2.1 8.3 0 0 8.3 6.3 16.7 11. No cover crop (Weeds), CC 0 2.1 0 0 0 4.2 18.8 0 2.1 6.3 2.1 4.2 12. Weeds, MC 0 0 0 0 0 25.0 16.7 0 0 2.1 12.5 0 13. Weeds + nematicide (Weedsnem), CC 0 0 0 2.1 0 2.1 29.2 0 25.0 8.3 8.3 0 14. Weedsnem, MC 4.2 6.3 0 0 0 0 2.1 0 16.7 4.2 4.2 12.5 LSD(p≤0.05) 19. 86

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row from grapevine bud break, full surface chemical control from berry set.




Table 28. Severity (%) of Phaeoacremonium spp. isolated from the roots of grapevines subjected to cover crops, selected for their potential to bio-fumigate the soil, managed according to two cover crop management practices.


6 May 2009

20 Aug. 2009

1 Dec. 2009

21 Apr. 2010

3 Aug. 2010

7 Dec. 2010

16 May 2011

23 Aug. 2011

30 Nov. 2011

8 May 2012

3 Sep. 2012

26 Nov. 2012

1. Avena sativa cv. Pallinup (oats), CC1 0 4.2 0 2.1 0 0 0 0 0 0 0 2.1 2. Oats, MC2 0 8.3 0 0 0 0 0 0 0 2.1 0 0 3. Sinapis alba cv. Braco (white mustard), CC 0 0 0 0 4.2 0 0 4.2 0 0 0 0 4. White mustard, MC 0 0 0 0 0 4.2 0 2.1 0 0 0 0 5. Brassica napus cv. AVJade (canola), CC 0 0 0 0 0 0 31.3 4.2 0 0 6.3 2.1 6. Canola, MC 0 6.3 16.7 0 0 0 0 0 0 0 0 2.1 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 0 0 2.1 2.1 6.3 0 0 0 4.2 0 0 8. Caliente, MC 0 0 0 0 0 0 0 0 0 2.1 6.3 0 9. Eruca sativa cv. Nemat (Nemat), CC 0 0 0 0 0 0 0 0 2.1 0 0 0 10. Nemat, MC 0 0 0 0 0 0 0 0 0 0 0 0 11. No cover crop (Weeds), CC 0 0 0 0 0 0 0 0 0 0 0 2.1 12. Weeds, MC 0 12.5 0 0 0 0 8.3 0 2.1 0 0 0 13. Weeds + nematicide (Weedsnem), CC 0 0 0 0 4.2 0 0 0 0 2.1

2.1 0

14. Weedsnem, MC 0 0 0 0 0 0 0 0 0 0 2.1 2.1 LSD(p≤0.05) 8.77




Table 29. Severity (%) of Pythium spp. isolated from the roots of grapevines subjected to cover crops, selected for their potential to bio-fumigate the soil, managed according to two cover crop management practices.


6 May 2009

20 Aug. 2009

1 Dec. 2009

21 Apr. 2010

3 Aug. 2010

7 Dec. 2010

16 May 2011

23 Aug. 2011

30 Nov. 2011

8 May 2012

3 Sep. 2012

26 Nov. 2012

1. Avena sativa cv. Pallinup (oats), CC1 0 0 0 0 0 0 0 0 0 0 0 0 2. Oats, MC2 0 0 0 0 0 0 0 0 0 0 0 0 3. Sinapis alba cv. Braco (white mustard), CC 0 0 0 0 0 0 0 0 0 0 0 0 4. White mustard, MC 0 0 0 0 0 0 0 0 0 0 0 0 5. Brassica napus cv. AVJade (canola), CC 0 0 0 0 0 0 0 0 0 0 0 0 6. Canola, MC 0 0 0 0 4.2 0 0 0 0 0 0 0 7. Brassica juncea cv. Caliente 199 (Caliente), CC 0 0 0 0 0 0 0 0 0 0 0 0 8. Caliente, MC 0 0 0 0 0 0 0 0 0 0 0 0 9. Eruca sativa cv. Nemat (Nemat), CC 0 0 0 0 2.1 0 0 4.2 0 0 0 0 10. Nemat, MC 0 0 0 0 0 0 0 0 0 0 0 0 11. No cover crop (Weeds), CC 0 0 0 0 0 0 0 0 0 0 0 0 12. Weeds, MC 0 0 0 0 0 0 0 0 0 0 0 0 13. Weeds + nematicide (Weedsnem), CC 0 0 0 0 0 0 0 2.1 0 0 0 0 14. Weedsnem, MC 0 0 0 0 0 0 0 0 0 0 0 0 LSD(p≤0.05) 1.15





Table 30. Effect of different soil management practices on the soil biological activity, expressed as the soil biological activity indeks, of a sandy to sandy loam soil in the Stellenbosch district

Treatment Soil biological activity index

9 Oct. 2009

19 Oct. 2009

27 Sep. 2010

7 Oct. 2010

10 Oct. 2011

20 Oct. 2011

19 Oct. 2012

1 Nov. 2012

23 Oct. 2013

1 Nov. 2013

1. Avena sativa cv. Pallinup (oats), CC1 218 237 182 136 149 237 226 221 226 82 2. Oats, MC2 177 244 215 119 232 244 252 247 232 82 3. Sinapis alba cv. Braco (white mustard), CC 210 237 197 91 153 230 227 234 244 49 4. White mustard, MC 173 235 201 99 199 239 232 241 235 47 5. Brassica napus cv. AVJade (canola), CC 201 234 165 80 137 226 237 247 247 52 6. Canola, MC 180 251 210 126 187 227 242 220 232 102 7. Brassica juncea cv. Caliente 199 (Caliente), CC 207 243 145 132 151 229 236 250 225 75 8. Caliente, MC 227 249 199 108 203 188 255 217 200 123 9. Eruca sativa cv. Nemat (Nemat), CC 204 217 190 99 121 231 246 236 219 129 10. Nemat, MC 171 243 199 148 212 202 250 238 238 141 11. No cover crop (Weeds), CC 172 185 187 106 118 237 238 241 239 86 12. Weeds, MC 174 233 229 113 217 195 253 202 226 175 13. Weeds + nematicide (Weedsnem), CC 184 199 176 126 201 225 253 241 252 205 14. Weedsnem, MC 168 247 187 112 227 236 234 227 212 142 LSD(p≤0.05) NS3 30 NS NS 48 NS NS NS NS 77

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row from grapevine bud break, full surface chemical control from berry set. 3Does not differ significantly at the 10% level.



significant increase or decrease in Pythium spp. Rhizoctonia spp., the cause of root rot, was only detected once (April 2010). Phytophthora was not detected.

Various pathogens were detected in the roots of grapevines used in this trial. The vineyard was seven years old at the beginning of the trial and one has to accept that grapevines will have some degree of infection at such an age. Many of these pathogens are already in propagation material or infect grapevines at various stages during the propagation process or once planted in a vineyard. However, it is a well-known fact that several factors can cause stress on vines where these “latent” infections are triggered to become more active to colonize infected vines and to cause decline and even death of severely infected vines. None of the treatments evaluated in this study significantly increased or decreased pathogen infections if one compares the severity levels at the end of four years to the severity levels detected at the beginning of the trial. Soil biological activity Although significant differences in the soil biological activity between treatments were observed on 19 October 2009, 10 October 2011 and 1 November 2013, no definite trends could be identified (Table 30). These results indicated that the glycosinolates released by the bio-fumigation cover crops did not have a negative effect on soil biological activity. Control potential of cover cops as green manure and their host Status for Meloidogyne javanica (root-knot nematodes) and Criconemoides xenoplax (ring nematodes) Meloidogyne javanica bioassays No significant differences (F(5,108) = 1.800; p = 0.118) were found between the interaction effects of the two bioassays (test date, and treatment), when they were analysed using a two-way ANOVA. Results from the two trial dates were then pooled and analysed, using a one-way ANOVA, with significant differences (F(5,108) = 3.862; p < 0.005) being found among the treatments. No significant differences were found between the root gall index of oats, canola, and the control (Fig. 3). All three crops obtained an average gall index of approximately 3, with did not differ significantly from one another, and neither were there any significant differences between the three treatments concerned and the Pallinup oats treatment. Criconemoides xenoplax bioassays On performing a two-way ANOVA on the results of the two different trial dates, the interaction was found to be not significant (F(5, 78) = 0.746; p = 0.591), and the main effects obtained could be interpreted. However, no significant differences were found between the various treatments involved (F(5.78) = 0.463; p = 0.802) (Fig. 4). Host status of cover crops for Meloidogyne javanica No significant difference (F(5, 104) = 2.155; p = 0.065) was found between the interaction effects (test date and galling) when they were analysed, using a two-way ANOVA. On pooling and analysing the data from the two trial dates, using a one-way ANOVA, however, significant differences were found among the treatments (F(5,110) = 64.454; p < 0.005) (Fig. 5).

All the cover crops differed significantly (p < 0.05) from the tomato control regarding their host status for M. javanica, with the control resulting in a severe expression of galls on the roots with a gall index of 5 (Fig. 5). The gall index for oats was significantly lower than that of canola (p < 0.01) and Caliente (p = 0.01), but it did not differ significantly from white mustard (p = 0.4) or Nemat (p = 0.8). Nemat was significantly lower in its M. javanica gall expression than the other crops, except oats.



Oats White mustard Canola Caliente 199 Nemat Control

Treatment

0

1

2

3

4

5G

all i

ndex

ab

b

a

a

b b

Figure 3. Meloidogyne javanica gall index (95% confidence interval) on tomato, treated with green manure of five different cover crops: oats (Avena sativa cv. Pallinup), white mustard (Sinapis alba cv. Braco), canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199), and Nemat (Eruca sativa cv. Nemat), incorporated into M. javanica-inoculated soil (one-way ANOVA; F (5,108) = 3.862; p < 0.005). Bars with the same letter did not differ significantly.between 50 to 100 galls each. White mustard (p = 0.0188), Caliente (p = 0.0248) and Nemat (p = 0.0188) had significantly lower gall indexes than canola. White mustard, Caliente, and Nemat. Visual inspection of the different root systems The root gall symptoms on the canola roots were very prominent, being comparable to the symptoms on the control roots (Fig. 6). The egg masses were prominent, with the distribution of the symptoms being uniform throughout the root system. The females, which were well embedded in the root system, were enclosed by the root cells. Prominent root galls and egg masses were also present in the root system of Caliente (Fig. 7). The females, which were deeply embedded in the root system, were well protected by the root cells. Fewer galls were present on the total root system of Pallinup oats, with the galls that were present being less prominent and more like a slight enlargement of the root tissue (Fig. 8). The female body was not totally embedded in the Pallinup oats root system, with a part of the body still being visible outside the root. The egg masses were more visual than were the galls on the roots. The distribution of the egg masses was not uniform throughout the root system, seeming to be situated closer to the soil surface. Very few galls or egg masses were present on the root system of the Nemat (Fig. 9). The galls that were present were only a slight enlargement of the root tissue, with few egg masses showing on the roots. Fewer galls and egg masses were present on the roots of the white mustard (Fig. 10), in comparison with those that were present on the Caliente (Fig. 7) and on the canola (Fig. 6), with the distribution throughout the root system not being uniform. The females were not fully embedded in the root system (Fig. 10),



Oats White mustard Canola Caliente 199 Nemat Control

Treatment

140

160

180

200

220

240

260

280

300

320C

. xen

opla

x pe

r 250

ml s

oil

a

a

a

a

a

a

Figure 4. Criconemoides xenoplax numbers (95% confidence interval) after treatment with green manure of five different cover crops: oats (Avena sativa cv Pallinup), white mustard (Sinapis alba cv. Braco), canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199), and Nemat (Eruca sativa cv. Nemat), incorporated into a C. xenoplax-inoculated soil. Bars with the same letter did not differ significantly. although they were more protected in comparison with the females that were present in the oats treatment (Fig. 8). The roots of the control plants were totally covered with galls, and the egg masses were very prominent (Fig. 11). The females, which were totally embedded in the root tissue, were well protected by the root cells. Host status of cover crops for Criconemoides xenoplax No significant difference (F(5,107) = 1.075; p = 0.105) was found between the interaction effects (test date, and treatment) when the analysis was undertaken by means of a two-way ANOVA. When the results from the two trial dates were pooled and analysed, using a one-way ANOVA, significant differences (F(6,122) = 8.233; p < 0.005) were found among the treatments (Fig. 12).

The tomato treatment had significantly higher (p < 0.01) C. xenoplax numbers than the other treatments, except for Nemat (Fig. 12). The C. xenoplax numbers in the cover crops did not differ significantly from the control (soil only). Canola had the least C. xenoplax at the time of evaluation, with the number concerned being significantly lower than that of Nemat (p = 0.003). General discussion White mustard, Caliente 199 and Nemat suppressed M. javanica gall formation. This supports the observations of Mojtahedi et al. (1993). The nematode-suppressing effect of different crops, after their incorporation into the soil, can differ drastically (McLeod & Steel, 1999; Piedra Buena et al., 2006).

Rahman et al. (2009) performed a trial with one-year-old Semillon grapevines planted in pots, which were inoculated with 500 M. javanica larvae after three months, and then left for 6



Oats White mustard Canola Caliente 199 Nemat Tomato

Treatment

0

1

2

3

4

5

6

Gal

l ind

ex

ad

ab

bbc

d

e

Figure 5. Gall index of Meloidogyne javanica (95% confidence interval) 60 days after inoculation of five different cover crops: oats (Avena sativa cv. Pallinup), white mustard (Sinapis alba cv. Braco), canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente), Nemat (Eruca sativa cv. Nemat), and tomato as control (one-way ANOVA; F

(5,104) = 68.919; p < 0.05). Bars with the same letter did not differ significantly.

Figure 6. Meloidogyne javanica galls and egg masses present on Canola (Brassica napus cv. AV Jade) roots.



Figure 7. Meloidogyne javanica galls and egg masses present on Caliente (Brassica juncea cv. Caliente 199) roots.

Figure 8. Meloidogyne javanica galls and egg masses present on Pallinup oats (Avena sativa cv. Pallinup) roots.



Figure 9. Meloidogyne javanica galls and egg masses present on Nemat (Eruca sativa cv. Nemat) roots.

Figure 10. Meloidogyne javanica galls and egg masses present on white mustard (Sinapis alba cv. Braco) roots.



Figure 11. Meloidogyne javanica galls and egg masses present on Tomato (Moneymaker) roots. months. Annually, the brassica seeds that were sown under the vines were slashed after 3 months, and then incorporated into the soil, for three consecutive years. The results indicated a gradual decline in the M. javanica population in the pots, with the best results being obtained in the third year. The vines in the pots that received the green manure also experienced a growth response, indicating the secondary effect of the green manure applications involved. Stirling and Stirling (2003) sowed brassicas in field soil and incorporated the green material into the soil at a depth of 180 mm after 10 weeks. A root gall index indicated a significant reduction in the M. javanica root galls, where brassicas were incorporated at an earlier stage than before. In the current study, canola did not show the same response to M. javanica, with regard to the root gallindex as the other brassica species. This was attributed to the fact that canola is not considered to have a very active composition of glycosinolates.

The fact that there was no significant difference in the C. xenoplax population, where the crop residues were applied to the inoculated medium, indicates that, in these specific bioassays, biofumigation cannot be considered to be as effective in suppressing C. xenoplax. In the M. javanica host trials, the control gall index was significantly higher than it was in case of the rest of the cover crops tested. This could have been expected, as the tomato cultivar that was chosen for this study is not known to be resistant to M. javanica, thus making it suitable as a control treatment. The gall symptom expression on the tomato plants, which was also very severe, gave a good impression of what a crop looks like when it is heavily infected with M. javanica. The use of these plants also exemplifies what can occur in terms of the impact of the wrong crop, if it is planted as part of a crop rotation, in intercropping, or in a crop rotation system, on a M. javanica population, as such a crop can host the full development of the latter’s life cycle, and also cause a population build-up in the soil.



OatsWhite mustard

CanolaCaliente 199

NematControl (soil only)

Tomato

Treatment

0

50

100

150

200

250

300

350

400

C. x

enop

lax

per 2

50 m

l soi

l

abab

a ab

bc

ab

c

Figure 12. Criconemoides xenoplax numbers (95% confidence interval) on five different cover crops, oats (Avena sativa cv. Pallinup), white mustard (Sinapis alba cv. Braco), canola (Brassica napus cv. AV Jade), Caliente 199 (B. juncea cv. Caliente 199), and Nemat (Eruca sativa cv. Nemat), 60 days after inoculation with nematodes. Inoculated soil was used as control, and tomato crops were used as an additional treatment (one-way ANOVA; F(6,122) = 8.2325; p < 0.005). Bars with the same letter did not differ significantly.

The results that were obtained in this study indicate that all cover crops tested were hosts for M. javanica, as galling, egg mass production, and egg hatching were observed for all the cultivars. However, the severity of the infection, as well as the expression of the symptoms, differed among the cultivars, with differences occurring in the M. javanica population build-up, where these cover crops were planted. The gall index of Nemat was less than 1 and significantly lower than that of the other brassica crops. Nemat can, therefore, be classified as a poor host for M. javanica. Nemat is also known as a trap root host (Melakeberhan et al., 2006). In the current study, however, M. javanica did complete its life cycle, and Nemat did not act as a catch crop in respect of preventing the development of a new generation.

Melakeberhan et al. (2006) showed that Nemat reduced the development and the reproduction of M. hapla in pot trials, where the evaluation was based, not only on the presence of root galls on the roots, but also in the suppression of all the developmental stages of M. hapla. The studies concerned also showed that there was a limiting effect on the development of the females, and, thus, in their reproduction on Nemat roots, resulting in no production of eggs. The current study indicated Nemat to be a poor host for M. javanica, which could have a significant suppressing impact on the population development in the field. In addition, Curto et al. (2005) indicated that Nemat reduced M. incognita reproduction, due to the interruption of the life cycle, or to the slowing down of the reproduction rate. The potential, therefore, exists for Nemat to be used in an integrated root-knot nematode management approach as a trap crop and also make a positive contribution through biofumigation (Curto et al., 2005).

The other three brassica species, being white mustard, canola and Caliente 199, did not differ significantly from one another, with all three having a low root gall index. The three



crops involved can, therefore, be classified as maintenance crops for M. javanica. These results correlate with the work that was done by Curto et al. (2005). Reproduction of M. javanica, on certain brassica crops, was compared to that on other crops that were not known to have biofumigation properties (Stirling & Stirling, 2003). The crops, that were included in these trials, were B. juncea cv. Nemfix (Indian mustard) , B. napus cv. Dunkeld (canola) , B. napus cv. Rangi (rape) , Sorghum bicolor × Sorghum Sudanese cv. Jumbo (forage sorghum) and L. esculentum cv. Tiny Tim (tomato) . They found that the brassica crops were hosts (maintenance crops) for M. javanica, but that they were significantly less so than were the tomato plants. Together with the forage sorghum, the number of eggs present in the case of the brassica crops was the lowest of all the crops considered. These results are all comparable with the results that were obtained in the current study.

Canola, although not being significantly different to Caliente and white mustard, was found to have the highest gall index rating of the brassica crops. It could, therefore, over the medium to longer term, sustain a population build-up of M. javanica better than the other brassica crops. Canola is considered to be a poor biofumigation crop, because of the impact that its GSL spectrum might have on its root susceptibility. Also, canola has a lower biofumigation potential, when it is applied as a biofumigation crop. The fact that canola is, therefore, not seen as the best option for the suppression of M. javanica must be taken into consideration when the exact aims of the cover crop programme employed are determined.

Although oats is not a brassica crop, it is widely accepted that the species has a poor host status for a wide range of soilborne problems, including M. javanica. This was confirmed in the current study, oats showed the second lowest root gall index of the crops studied and did not differ significantly from the Nemat treatment. Oats can, however, not be classified as a non-host, or as a trap crop, as root gall formation and egg mass production occur on the roots. In the current study, the egg masses seemed to be situated closer to the soil surface and closer to the point of inoculation than with the other crops under investigation. The finding might have indicated the presence of a large population of M. javanica, prior to the development of root gall symptoms and egg masses on the root system. It is, nevertheless, clear, from a cover crop or rotation crop perspective, with a focus on M. javanica population suppression, that oats are a viable option, and that they can be used as part of a cover crop rotation programme, without the risk of stimulating the M. javanica population in the soil where it is planted.

The results obtained in this study indicate that Nemat and oats can successfully be used as part of an IPM programme to help suppress the population build-up of M. javanica in the soil.

Of all the cover crop treatments in the current study, the C. xenoplax numbers were found to be the highest in Nemat, and significantly higher than that which occurred in the canola treatment. However, no significant difference was found between Nemat and the soil-alone treatment, indicating that, even though the Nemat tended to increase the C. xenoplax population, such an increase does not necessarily indicate that Nemat is a good host for C. xenoplax, but, rather, that it can be classified as a maintenance crop for C. xenoplax. A positive trend to emerge from the data is the fact that the canola treatment resulted in the lowest number of C. xenoplax, thus enabling it to be classified as a poor host for the nematode concerned. It can be expected that, if canola is planted as part of a cover crop system, it will neither stimulate a C. xenoplax population build-up, nor will it maintain the population, but it will, rather, have a suppressing effect on the population. In this regard, Caliente, oats and white mustard show a similar, but weaker, trend. The effect of the cover crops and management practices on the plant-parasitic nematodes in the vineyard The nematode species identified in the soil samples were; Meloidogyne incognita (root-knot nematode), C. xenoplax (ring nematode), Xiphinema spp. (dagger nematode), Helicotylenchus spp. (spiral nematode). Of these, C. xenoplax and M. incognita were the most prevalent. The extraction of Pratylenchus spp. was only done for the first year, but it was discontinued, because of insignificant population numbers. During the fourth and fifth season, only C.



xenoplax was counted and reported upon, due to the insignificant numbers of the other nematodes.

M. incognita No significant differences were found between the different cover crops with regard to the suppression of M. incognita, as indicated by the 60 day sampling period for 2009, 2010 and 2011 (Table 31).

As indicated, the M. incognita numbers were very low (even in the vine row), but a declining trend was observed from 2009 to 2011 for canola (CC), Caliente (CC) and Nemat (MC) treatments. Table 31. Root-knot nematode population in the vine row: Y (year) × T (time) × Pos (position) x CP (crop/practice) interaction sixty days after the cover crops were controlled.

Treatment Number of nematodes in 250cc soil

2009 2010 2011 1. Avena sativa cv. Pallinup (oats), CC1 8 42 20

2. Oats, MC2 26 18 84

3. Sinapis alba cv. Braco (white mustard), CC 36 38 36

4. White mustard, MC 10 28 46

5. Brassica napus cv. AVJade (canola), CC 80 16 44

6. Canola, MC 14 26 32

7. Brassica juncea cv. Caliente 199 (Caliente), CC 90 32 38

8. Caliente, MC 24 38 16

9. Eruca sativa cv. Nemat (Nemat), CC 14 26 32

10. Nemat, MC 82 16 42

11. No cover crop (Weeds), CC 30 24 26

12. Weeds, MC 24 32 70

13. Weeds + nematicide (Weedsnem), CC 38 24 18

14. Weedsnem, MC 44 14 42

LSD (p≤0.05) 31 1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set. C. xenoplax. (ring nematodes) The ring nematode populations in the work row were in all cases very low (significantly lower than those in the vine row), which did not allow for specific conclusions or trends regarding the impact of the cover crops on these nematodes to be made (data not shown). The ring nematode populations in the vine row are shown in Figures 13 to 19.

Three periods were considered, namely 1) April to Day 0 in a specific year, which indicates the impact that the actively growing cover crops and winter weeds had on the ring nematode numbers, 2) Day 0 to Day 60 for a specific year, indicating the impact of the cover crops after the management practices were applied and 3) Day 60 to April the following year, indicating the ability of the ring nematodes to recover during the ‘inter-treatment period’.



April to day 0 During 2010, the ring nematode population declined in canola (CC) and Caliente (MC) (Fig. 13 & 14). This trend was observed for all treatments during 2011 and 2012, with the exception of Nemat (CC), white mustard (MC) and Weedsnem (CC) during 2011 (Fig. 13 to 18). During the relatively wet winter of 2013 (Table 7) this trend was observed in the two Nemat treatments, white mustard (CC), Pallinup oats (CC), Weedsnem (MC) and Weeds (CC) (Fig. 15 to 19). The ring nematode population increases during the growing season of the cover crops were on average 61% for canola, 35% for white mustard, 26% for the weeds, 20% for Pallinup oats, 17% for Caliente and 7% for Nemat. Day 0 to Day 60 A continuous decline in ring nematode numbers from day 0 to day 60 was detected throughout the study for canola (MC) (Figure 13). This was also observed for white mustard (MC) and Weedsnem (CC), with the exception of 2013 and 2009, respectively (Figures 16 & 18). Oats (CC) resulted in the ring nematode numbers declining continuously from day 0 to day 60 during 2009, 2010 and 2011 (Figure 17). As far as the other treatments are concerned, the ring nematode numbers were suppressed irregularly. Day 60 to April With the exception of canola (CC) in 2009/10, as well as the two white mustard treatments, Nemat (CC) and Weedsnem (CC) in 2011/12, the ring nematode populations repeatedly increased from day 60 to March the following year (Figures 13 to 19). The rainfall during this period varied between 97 mm and 163 mm (Table 30), which seemed sufficient to allow the ring nematode population to recover at least partially. The average percentage increase during this period was much higher than during the winter (April to Day 0), namely 247%. This is an indication that a follow-up treatment with a nematicide is necessary in an attempt

Figure 13. The effect of two management practices, namely CC and MC (See Table 2), applied to canola (Brassica napus cv. AV Jade) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.



Figure 14. The effect of two management practices, namely CC and MC (See Table 2), applied to Caliente (Brassica juncea cv. Caliente 199) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.

Figure 15. The effect of two management practices, namely CC and MC (See Table 2), applied to Nemat (Eruca sativa cv. Nemat) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.



Figure 16. The effect of two management practices, namely CC and MC (See Table 2), applied to White mustard (Sinapis alba cv. Braco) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.

Figure 17. The effect of two management practices, namely CC and MC (See Table 2), applied to oats (Avena sativa L. cv. Pallinup) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.



Figure 18. The effect of two management practices, namely CC and MC (See Table 2), applied to Weeds (winter growing weeds) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.

Figure 19. The effect of two management practices, namely CC and MC (See Table 2), applied to Weedsnem (winter growing weeds combined with the application of a nematicide in the vine row during grapevine bud break) on the ring nematode (Criconemoides xenoplax) population in a sandy to sandy loam soil near Stellenbosch from Day 0 in 2009 to Day 60 in 2013. LSD (p ≤ 0.05) = 252.



to maintain the downward trend achieved during the sixty day period after grapevine bud break. Biofumigation should, therefore, not be applied in isolation, but as part of an integrated nematode control program. Day 0 2009 to Day 60 2013 A significant decline in the ring nematode population was observed from Day 0 in 2009 to Day 60 in 2013, irrespective of the treatments applied (Figures 13 to 19), with the exception of white mustard (MC), although the rainfall was higher during the 2012/13 and 2013/14 seasons than during the 2010/11 and 2011/12 seasons (Table 31). It is possible that the roots of the permanent sward, which was maintained in the grapevine inter row before the treatments were applied by regular slashing, supplied an additional food source to the ring nematodes throughout the year. In contrast, the soil management practices applied during the trial removed this food source during spring and early summer (also in the Weeds treatment in which no biofumigation crop or nematicide were applied), which reduced the availability of roots during the grapevine growing season. Soil microbial activity The bacterial diversity and community structure were the two variables used to express and compare the soil microbial status between the treatments and seasons during the 2009-2012 seasons. From the combined ARISA and amplicon sequence data, it was shown that a number of bacterial species in the sample influence the diversity patterns. Diversity is expressed using the Shannon diversity index and indicate the relative abundance of Operational Taxonomic Units (OTU’s) in a sample. An OTU may in some cases represent a single species, but in most cases can represent multiple species, depending on the protocol use. In this case, an OTU represents the unique peaks differentiated by ARISA protocol. Bacterial structure in this case is defined as the presence or absence of specific bacterial OTU’s and their relative abundance in a sample. Simply stated, which bacteria are present in the sample and in what ratio. Bacterial diversity across all years and all treatments were not significantly different (Fig 20). In other words, the number of taxa remained constant, regardless of the treatment or the time the samples were taken after treatment.

On the other hand, bacterial community structure appears to change over years (Fig 21). This implies that the bacterial community composition changed with time over the entire experimental site. No differences could, however, be seen in the community structure between different treatments of the same year. No significant differences could also be seen within treatments for the specific period of sampling (0 - 60days). The addition of organic material in the form of cover crops after 2009 (April sample) probably accounts for this shift, however, there is no statistical evidence for this and there may be another factor driving the shift in bacterial community structure across the vineyard.

During 2012, a more intensive sampling protocol was followed, and more repetitions per treatment were sampled. In addition, vine rows and working rows were independently analysed and a similar shift in the community composition was detected in the 2012 samples, than from previous years. Separate analysis of the vine rows and working rows, showed that these areas were occupied by distinct bacterial communities (Fig 22). This was investigated in more detail during the 2013/2014 growing season. The ARISA data comparing the working rows and the vine rows was used to select samples for high throughput sequencing (Fig. 23). The sample selection for sequencing fell within the 75% confidence limit of the clusters observed after analysis of the ARISA data. The most significant result seen after analysis was the association of the genera Acinetobacter, Bacillus, Massilia, Naxibacter, Paenibacillus and Streptomyces with the bench rows (p<0.05) and made up a large number of the total reads from vine row samples. The working row showed a significant association with the genera Actinomycetospora and Nitrospira (p<0.05). These differences within the vine row and working row samples correspond to the main difference in bacterial community structure according to the community ordination plot



Figure 20: Microbial diversity from 2009 – 2012 base on ARISA data. No differences were observed in overall microbial diversity across the treatments, seasons and years. Figure 21: MDS plot showing the shift (arrow) in community structure of all treatments from 2009 – 2012. This shift in community structure does not correlate with the soil chemistry or treatment and may be the result of the continuous overall treatment of the vineyard.



Figure 22: MDS plot illustrating the differences in microbial composition within the vine row (marked blue) and the work row (marked red). These results represent four different treatments, which were intensively sampled and analyzed separately. (Figure 24). The priori ANOSIM test also confirmed that the vine row and working row sample groups were significantly different (R = 0.9, p<0.05). Acinetobacter, Bacillus, Massilia, Naxibacter, Paenibacillus and Streptomyces are all well documented bacterial groups in soil. Acinetobacter, Bacillus, Massilia spp. are known for their ability to degrade a wide variety of compounds and is commonly isolated from soils. Acinetobacter has been documented to be able to solubilise nitrogen and phosphate, contributing to the overall health of plants (Abdel-El-Haleem, 2004; Mardad et al, 2014). Bacillus spp perform a variety of functions including absorbing heavy metals, and excreting auxins and siderophores to manipulate surrounding plants and bacteria. Massilia, Naxibacter and Paenibacillus have recently been isolated and appear to be involved in various aspects of plant growth promoters. These bacteria secretes a variety of compounds that can induce growth promotion in plants, but also play important role in decomposition in soil, through the excretion of a variety of enzymes. Streptomyces represents a large group of bacteria and can repress fungal growth, both pathogen and mycorrhizal, in soil (Bontemps et al., 2013).

In contrast, the working row were dominated by Actinomycetospora and Nitrospira. Actinomycetospora is able to fix nitrogen and solubilize phosphate, and presence of the rotation crops, most likely select for these organisms. Nitrospira is well documented for its role as nitrite oxidizer in soils, and are usually present at low concentrations. Addition of nitrogen, coupled with an increase in soil moisture and CO2 have been linked to this group becoming dominant. Both these groups are commonly isolated from grasslands, agricultural soils and forests (Koch et al. 2015; Levy-Booth et al., 2014, Le Roux et al, 2016). Grapevine performance Shoot mass and grape yield The average shoot growth increased annually from August 2009 to August 2012, which indicated that the fertilisers applied during the study had a significant effect on the vegetative growth of the grapevines (Figure 25). The average shoot mass of the grapevines where CC was applied was higher than that of the grapevines where MC was applied (Figure 26). Although not significant, the effect of the species on the vegetative growth of the grapevines was as follows: canola > Nemat > Caliente > Pallinup oats > Weeds > Weeds,nematicide > white mustard (Figure 27).

The average grape yield increased by 270% from the 2010 to the 2011 harvest (Figure 28). This was attributed to the fertiliser program initiated to address the nutrient



Figure 23: The number of normalized reads of the most abundant genera (> 1% of the total sequence reads) in the vine row and the working row samples.

0

200

400

600

800

1000

1200

1400

1600No

rmali

sed

read

s

Genus (> 1% total reads)

Working row

Vine row



Figure 24: Community ordination plot of working row and vine row (vine row) samples using factor analysis. There is a clear separation of communities based on the area (vine row or working row) irrespective of the treatment. needs of the grapevines. The size of the 2012 harvest was similar to that of 2011. From 2012 to 2013, however, an overall decline was observed. Despite the observed decline, the 2013 harvest was still higher than that of 2010. As observed for the shoot mass, the grape yield of the grapevines in which CC was applied was higher than that of the grapevines where MC was applied (Figure 29). Although not significant, the effect of the species on the grape yield was as follows: Nemat > Caliente > canola > Pallinup oats > Weeds,nematicide > Weeds > white mustard (Figure 30). Leaf nutrient status Throughout the study, the level of N in the leaf blades (Table 32) of all the treatments was within the norm for South African vineyards (Saayman, 1981). The level of N in the petioles exceeded the norm for South African vineyards in 2009, but only in the white mustard, canola and Caliente treatments, as well as Nemat (CC) in 2010 (Table 32). During 2011 and 2012 the level of N in the petioles of all the treatments were below the norm, with the exception of white mustard (CC) in 2011 and white mustard (MC) in 2012. The lower values observed during 2010, but especially during 2011 and 2012, was attributed to the increase in shoot mass observed throughout the study (Figure 25).

Although the P concentration of the 0-150 mm soil layer (Table 4) could provide more than adequately in the need of the grapevines, the P concentration in the leaf blades was lower than the generally accepted norm in all the treatments in 2011 and 2012, with the exception of the Caliente treatments in 2011 and Weeds (CC) in 2012 (Table 33). The level of P in the petioles (Table 33) remained approximately a third of the generally accepted norm (Saayman, 1981), despite the application of P at the end of April 2011 and early May 2012 (Table 3), which resulted in a luxurious supply of P 0-150 mm soil layer from 2011 onwards



Fig. 25. The effect of season on the average shoot mass of a drip irrigated Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch in the Western Cape, South Africa.

Fig. 26. The effect of the management practice applied on the average shoot mass of a drip irrigated Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch in the Western Cape, South Africa.



Fig. 27. The effect of species on the average shoot mass of a drip irrigated Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch in the Western Cape, South Africa.

Fig. 28. The effect of season on the average grape yield of a drip irrigated Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch in the Western Cape, South Africa.



Fig. 29. The effect of the management practice applied on the average grape yield of a drip irrigated Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch in the Western Cape, South Africa.

Fig. 30. The effect of species on the average grape yield of a drip irrigated Shiraz/101-14 vineyard established on a sandy to sandy clay loam soil near Stellenbosch in the Western Cape, South Africa.



Table 32. The effect of cover crops and the management thereof on the nitrogen (N) levels in the leaf blades and petioles of Shiraz/101-14 vines established on a sandy soil near Stellenbosch.

Treatment N (%)

Leaf blades Petioles

2009 2010 2011 2012 2009 2010 2011 2012

1. Avena sativa cv. Pallinup (oats), CC1 3.10 2.65 2.77 2.59 1.18 0.90 0.82 0.70

2. Oats, MC2 3.18 2.64 2.64 2.54 1.10 0.94 0.82 0.75

3. Sinapis alba cv. Braco (mustard), CC 3.08 2.77 2.67 2.60 0.99 1.04 0.97 0.80

4. Mustard, MC 2.88 2.69 2.66 2.50 1.01 0.97 0.87 0.99

5. Brassica napus cv. AVJade (canola), CC 2.99 2.78 2.78 2.59 1.15 1.01 0.87 0.88

6. Canola, MC 3.02 2.65 2.72 2.83 1.12 0.98 0.82 0.89

7. Brassica juncea cv Caliente 199 (Caliente), CC 3.00 2.76 2.65 2.73 1.09 1.02 0.86 0.82

8. Caliente, MC 3.07 2.73 2.70 2.64 1.21 1.00 0.82 0.87

9. Eruca sativa cv. Nemat (Nemat), CC 3.15 2.70 2.69 2.63 1.10 0.97 0.82 0.74

10. Nemat, MC 3.03 2.77 2.60 2.64 1.21 0.94 0.78 0.66

11. No cover crop (Weeds), CC 3.10 3.28 2.73 2.64 0.99 0.86 0.84 0.61

12. Weeds, MC 3.02 2.61 2.59 2.62 1.05 0.80 0.81 0.56

13. Weeds + nematicide (Weedsnem), CC 2.87 2.91 2.50 2.67 2.35 0.84 0.79 0.59

14. Weedsnem, MC 2.10 2.71 2.53 2.58 2.64 0.82 0.80 0.57

LSD (p≤0.05) 0.29 NS3 0.154 NS 0.26 0.12 0.09 0.16 1Full surface chemical control from just before budbreak. 2Chemical control vine row, mechanical incorporation in work row just before bud break, full surface chemical control from berry set. 3Data does not differ significantly at the 10% level. 4Data differ significantly at the 10% level.



Table 33. The effect of cover crops and the management thereof on the phosphate (P) levels in the leaf blades and petioles of Shiraz/101-14 vines established on a sandy soil near Stellenbosch.

Treatment P (%)


2009 2010 2011 2012 2009 2010 2011 2012


2. Oats, MC2 0.26 0.25 0.19 0.20 0.22 0.20 0.12 0.16


4. Mustard, MC 0.24 0.25 0.20 0.20 0.17 0.18 0.13 0.15


6. Canola, MC 0.23 0.25 0.21 0.19 0.20 0.22 0.17 0.19


8. Caliente, MC 0.24 0.28 0.22 0.20 0.23 0.26 0.20 0.20


10. Nemat, MC 0.23 0.25 0.20 0.20 0.22 0.18 0.13 0.20

11. No cover cropp (Weeds), CC 0.24 0.25 0.21 0.22 0.21 0.21 0.17 0.25

12. Weeds, MC 0.23 0.25 0.19 0.20 0.22 0.21 0.19 0.21


14. Weedsnem, MC 0.23 0.28 0.19 0.20 0.19 0.22 0.13 0.17

LSD (p≤0.05) 0.03 0.02 NS3 NS 0.054 NS 0.04 NS 1Full surface chemical control from just before budbreak. 2Chemical control vine row, mechanical incorporation in work row just before bud break, full surface chemical control from berry set. 3Data does not differ significantly at the 10% level. 4Data differ significantly at the 10% level.



Table 34. The effect of cover crops and the management thereof on the potassium (K) levels in the leaf blades and petioles of Shiraz/101-14 vines established on a sandy soil near Stellenbosch.

Treatment K (%)


2009 2010 2011 2012 2009 2010 2011 2012


2. Oats, MC2 0.86 0.96 0.93 0.81 1.34 0.83 0.91 0.97


4. Mustard, MC 0.76 0.92 0.89 0.80 1.35 0.75 0.74 0.91


6. Canola, MC 0.89 0.98 0.90 0.82 1.44 0.80 0.88 1.29


8. Caliente, MC 0.83 0.93 0.83 0.88 1.33 0.73 0.72 1.29


10. Nemat, MC 0.89 1.05 0.83 0.82 1.52 0.89 0.78 0.98

11. No cover crop (Weeds), CC 0.82 1.07 0.92 0.94 1.39 0.88 1.05 1.22

12. Weeds, MC 0.84 0.97 0.89 0.88 1.33 0.74 0.98 1.14


14. Weedsnem, MC 0.86 1.18 1.02 0.95 1.36 0.75 0.97 1.09

LSD (p≤0.05) 0.10 0.15 NS3 0.10 NS NS 0.17 0.22 1Full surface chemical control from just before budbreak. 2Chemical control vine row, mechanical incorporation in work row just before bud break, full surface chemical control from berry set. 3Data does not differ significantly at the 10% level.




(Table 4). Despite significant differences that occurred between treatments in some of the years, no trends were observed.

The level of K in the leaf blades of all the treatments remained slightly below the generally accepted norm throughout the study, with the exception of the two Weeds, nematicide treatments in 2010 (Table 34). Although the level of K in the petioles was at an acceptable level in 2009, a slight deficiency was observed during the rest of the trial, with the exception of Weeds (CC) in 2012. This trend was attributed to the continuous increase in shoot growth measured from year 2009 to 2012 (Figure 25). As far as the level of K in the leaf blades and petioles are concerned, no significant trends were observed between treatments.

The above-mentioned results confirm the importance of monitoring the plant nutrient status annually and that the application of K and N at the flowering stage of grapevines growing on sandy soils should be considered favourably where the levels are below the generally accepted norms. Nutrient status of the juice The level of N in the juice was very low for the duration of the study (Table 35), despite the application of 28 kg N during grapevine flowering (2010) and grapevine full bloom (2011) (Table 3). Nitrogen was not applied during grapevine full bloom in 2012 (Table 3) due to the continuous increase in the vegetative growth of the grapevines (Figure 25), which could lead to infertility and a decrease in the harvest over the long-term (Figure 28). The level of N in the juice indicated that the application of N during the growing season of the grapevines should definitely Table 35. The nitrogen (N) levels in the juice during the harvests of 2010, 2011, 2012 and 2013.

Treatment N content of the juice (mg/L)

2010 2011 2012 2013

1. Avena sativa cv. Pallinup (oats), CC1 92 279 249 985

2. Oats, MC2 152 309 240 847

3. Sinapis alba cv. Braco (white mustard), CC 138 364 246 743

4. White mustard, MC 180 408 242 636

5. Brassica napus cv. AVJade (canola), CC 155 403 274 602

6. Canola, MC 115 423 207 458

7. Brassica juncea cv. Caliente 199 (Caliente), CC 94 515 306 547

8. Caliente, MC 133 589 246 499

9. Eruca sativa cv. Nemat (Nemat), CC 122 682 220 454

10. Nemat, MC 95 802 273 609

11. No cover crop (Weeds), CC 143 776 265 720

12. Weeds, MC 116 497 191 487

13. Weeds + nematicide (Weedsnem), CC 77 635 236 482

14. Weedsnem, MC 51 369 192 538

LSD (p≤0.05) 33 304 37 186 1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set.

Progress report 81


be considered, as long as the vegetative growth of the grapevines is in balance with the harvest. The P levels in 2011 and 2012 being above the generally accepted norm (Table 36) is an

indication that the grapevines benefitted from the luxurious supply in the 0-150 mm soil level (Table 4). The K applied from the grapevine flowering stage in 2010 to grapevine full bloom 2012 (Table 3), did improve the K levels in the must during the 2011 and 2012 harvests (Table 37). The results indicate that K could probably have been applied every year during post-harvest and grapevine full bloom, without jeopardizing the quality of the must. Wine quality

The treatments had no effect on the quality of the wine produced during the 2011 harvest (Table 38). As the grape yield did not differ between cover crop x management practice treatments during the 2011, 2012 and 2013 harvests, no wine was made during 2012 and 2013.

Table 36. The phosphate (P) levels in the juice during the harvests of 2010, 2011, 2012 and 2013.

Treatment P content of the juice (mg/L)

2010 2011 2012 2013

1. Avena sativa cv. Pallinup (oats), CC1 229 98 148 48

2. Oats, MC2 239 85 140 57

3. Sinapis alba cv. Braco (white mustard), CC 241 101 135 59

4. White mustard, MC 273 94 144 60

5. Brassica napus cv. AVJade (canola), CC 202 108 140 64

6. Canola, MC 133 99 129 59

7. Brassica juncea cv. Caliente 199 (Caliente), CC 132 117 141 62

8. Caliente, MC 93 91 144 74

9. Eruca sativa cv. Nemat (Nemat), CC 53 86 140 66

10. Nemat, MC 43 76 131 62

11. No cover crop (Weeds), CC 52 96 140 83

12. Weeds, MC 62 84 132 86

13. Weeds + nematicide (Weedsnem), CC 40 88 130 75

14. Weedsnem, MC 44 100 132 74

LSD (p≤0.05) 33 18 NS3 15 1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set. 3Data does not differ significantly at the 10% level. d) CONCLUSIONS During this study, it became clear that the annual application of P should be avoided, as it may lead to exceptionally high levels of this element in the 0-75 mm soil layer an elevated levels in the 75-150 mm soil layer. Caliente and Nemat should not be incorporated into the soil, but rather be controlled chemically during budbreak (CC) to promote an increase in the organic C of these sandy top soils (0-75 mm). It seemed that the roots of oats, white mustard and canola made a significant contribution to the organic matter content in the deeper soil layers (150-300 mm).

Progress report 82


Treatment K content of the juice (mg/L)

2010 2011 2012 2013 1. Avena sativa cv. Pallinup (Pallinup oats), CC1 450 973 903 523 2. Pallinup oats, MC2 371 1019 936 664 3. Sinapis alba cv. Braco (white mustard), CC 303 1180 1031 510 4. White mustard, MC 339 1024 967 431 5. Brassica napus cv. AVJade (canola), CC 476 1046 1001 428 6. Canola, MC 728 1018 912 465 7. Brassica juncea cv. Caliente 199 (Caliente), CC 587 1052 1082 486 8. Caliente, MC 675 987 971 463 9. Eruca sativa cv. Nemat (Nemat), CC 471 804 986 434 10. Nemat, MC 179 822 962 492 11. Weeds, CC 282 921 1078 520 12. Weeds, MC 246 1265 963 485 13. Weeds, nematicide, CC 167 1236 981 500 14. Weeds, nematicide, MC 296 1279 1080 587 LSD (p≤0.05) 198 232 107 92

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set.

The quality of the seedbed, as well as relatively low winter temperatures, had a greater effect on the performance of the small seeded white mustard, canola, Caliente and Nemat, than on the larger seeded oats. On sandy to sandy clay loam soils, the cover crops should receive N, K and P from just before planting up until the six leaf stage to maximise their performance. However, the application of P should be done judiciously, as it may accumulate and reach high concentrations in the 0 to 75 mm and 75 to 150 mm soil layers within a very short period of time.

All the cover crop species suppressed the winter growing weeds effectively after five seasons, with immediate and sustainable effective control being achieved with oats and Caliente. At the end of the first winter (2009), ryegrass was effectively suppressed in the CC Table 37. The potassium (K) levels in the juice during the harvests of 2010, 2011, 2012 and 2013.treatments of oats and white mustard, while this species was either the most dominant or second most dominant species in all the treatments, except Caliente (MC). During the following two seasons, it was observed that chemical control just before budbreak played a major role in lowering the stand of ryegrass in the following season. Total suppression of ryegrass was achieved in the CC treatments of oats and Nemat in the third year of application. The dominance of ryegrass was terminated in 2012 (fourth season) by the application of a grass specific herbicide approximately a fortnight after sowing the broadleaf cover crops (end of May). The chemical control of ryegrass most probably facilitated the dominance of musk heron’s bill. The cover crops being established as late as 23 May during 2013, prevented the ryegrass from regaining its dominance in any treatment. After five winters, ryegrass was totally eradicated from the oats treatments, white mustard (CC) and Nemat (CC).

Chemical control of the cover crops or weeds seems to improve the control of summer growing weeds. Caliente, canola, white mustard and Nemat, which were selected primarily for their biofumigation properties, can be included in a cover crop rotation system for grapevines, without compromising weed control efficacy. During the first season of implementing the treatments, either musk heron’s bill or ryegrass dominated the weed spectrum during grapevine

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Table 38. The effect of cover crops and the management thereof on wine quality of Shiraz/101-14 vines established on a sandy soil near Stellenbosch, as determined during August 2011.

Treatment Wine quality (value out of 10)3

Colour Overall intensity

Overall quality

1. Avena sativa cv. Pallinup (Pallinup oats), CC1 5.38 5.67 4.31 2. Pallinup oats, MC2 5.98 5.46 4.26 3. Sinapis alba cv. Braco (white mustard), CC 6.29 5.46 4.57 4. White mustard, MC 5.60 4.94 4.09 5. Brassica napus cv. AVJade (canola), CC 5.48 5.20 4.18 6. Canola, MC 5.69 5.28 4.27 7. Brassica juncea cv. Caliente 199 (Caliente), CC 6.14 5.50 4.76 8. Caliente, MC 6.35 5.83 4.73 9. Eruca sativa cv. Nemat (Nemat), CC 6.27 5.87 4.72 10. Nemat, MC 5.79 5.50 4.20 11. Weeds, CC 6.37 5.59 4.58 12. Weeds, MC 6.05 5.31 4.47 13. Weeds, nematicide, CC 5.13 4.93 3.96 14. Weeds, nematicide, MC 6.42 5.52 4.90

1Full surface chemical control from grapevine budbreak. 2Chemical control vine row, mechanical incorporation in work row during grapevine budbreak, full surface chemical control from berry set. Data did not differ significantly at the 10% level berry set (early summer). Musk heron’s bill was totally suppressed in all the treatments during berry set within two seasons. Ryegrass was suppressed totally during berry set in all the CC treatments by 2011. This trend persisted in the CC treatments of oats, Caliente and Nemat during 2012. It can, therefore, be accepted that CC plays an important role in the control of this problem weed from budbreak to berry set. It seems that the application of CC facilitated the eventual dominance of crab fingergrass during grapevine berry set. During the pre-treatment measurement at the end of summer 2009 (post-harvest), Natal red-top, a perennial grass, was the most dominant species in all the treatments except Nemat (MC), in which it was absent. This species lost its post-harvest dominance from the 2009/10 season onwards. The mulch of the cover crops used in the trial did help to suppress erect Boerhavia effectively in April 2011. It seems that the relatively low summer rainfall during the 2010/11 season compared to that of the 2009/10, 2011/12 and 2012/13 seasons, allowed pimpernel to appear in April 2011 and dominate some of the treatments. This coincided with the disappearance of common couch and prostrate knotweed, who did not cope well with the dryer summer. The relatively high summer rainfall during the 2011/12 and 2012/13 seasons, seemed to allow these two perennials to recover and dominate in some of the treatments. A trend was observed where crab fingergrass, common couch and prostrate knotweed seemed to establish itself better during late summer where mechanical cultivation was applied during budbreak (MC), thereby leaving the soil mulch-free during the summer. The average weed stand being reduced to less than 10% of the stand before the treatments were applied, illustrated the benefit of weed control applied during grapevine berry set. The doubling of the weed stand at post–harvest from the 2009/10 season to the 2001/12 and 2012/13 seasons, which had a higher summer rainfall is an indication that weed control in the period from berry set to post-harvest should be considered if the summer rainfall is relatively high.

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The bio-assay indicated that canola, and to a lesser extent Caliente, oats, white mustard and Nemat can play an essential role in an IPM programme for plant-parasitic nematodes. A characteristic that is very important to keep in mind, in this regard, is the host status of the specific crop. Whether it is applied as a cover crop in vineyards or orchards, during the dormant stage of the crop; as a rotation crop in a cash-cropping system; or used prior to the replanting of trees, where the replant disease complex plays a role, the host status of the crop used is a critical factor for breaking the life cycle of certain soilborne biotic problems. The use of Nemat as a cover, or rotation, crop can be beneficial in suppressing M. javanica. In the case of C. xenoplax, one can be expected to see a decline in the population over time when canola is implemented in terms of a cover crop system.

As cover crops can play a very important role in IPM, in future research it would be beneficial to consider the crop host status for most cover crops that form part of cover crop, or rotation, systems, as well as to look at the possibility of combining such considerations this with other chemical and biological options in establishing a long-term solution for nematode management.

During winter, Nemat, Caliente 199 and oats did not facilitate a ring nematode population increase in the vineyard to the same extent as the weeds growing in this region. In some years, the ring nematode population even showed a decline during the harvests of the 2010, 2011, 2012 and 2013 winter, whether a cover crop was established or not. During the early grapevine growing season, the most effective ring nematode suppression was achieved when canola and white mustard were mechanically incorporated into the soil, as well as where a nematicide was applied or oats was sown and combined with full surface chemical control. However, the drastic increase in the ring nematode population during summer and early autumn indicates that a follow-up treatment with a nematicide is necessary in an attempt to maintain the downward trend achieved during the sixty day period after grapevine bud break. Biofumigation should, therefore, not be applied in isolation, but as part of an integrated nematode control program. Controlling the weeds/cover crops during the grapevine growing season may help reduce the ring nematode population over the medium term.

The soil pathogen status and biological activity was not affected by the treatments applied.

The shoot mass and grape yield was higher for the grapevines in which CC was applied compared to MC. The element content of the leaves and juice, as well as wine quality was not affected. LITERATURE CITED Abdel-El-Haleem, D. (2004). Acinetobacter: environmental and biotechnological applications.

African J. Biotechnol. 2, 71-74. Anonymous, 2013. Canola production manual. http:\\

www.overbergagri.co.za/documents/agri/canola%20manual.pdf. Downloaded 4 July 2014.

Bontemps, C., Toussaint, M., Revol, P. V., Hotel, L., Jeanbille, M., Uroz, S. & Leblond, P. (2013). Taxonomic and functional diversity of Streptomyces in a forest soil. FEMS microbiology letters, 342, 157-167.

Booysen, J.H., Steenkamp, J. & Archer, E., 1992. Names of vertical trellising systems (with abbreviations). Wynboer September, 15.

Brown MV, Schwalbach MS, Hewson I, Fuhrman JA (2005) Coupling 16S-ITS rDNA clone libraries and ARISA to show marine microbial diversity; development and application to a time series. Environ. 7, 1466-1479.

Campbell, C.R. & Plank, C.O., 1998. Preparation of plant tissue for laboratory analysis, Y.P. Kalra (Ed.). Handbook of reference methods for plant analysis, pp 37-49. CRC Press, Boca Raton.

Cardinale M, Brusetti L, Quatrini P, Borin S, Puglia AM, Rizzi A, Zanardini E, Sorlini C, Corselli C, Daffonchio D (2004) Comparison of Different Primer Sets for Use in Automated Ribosomal Intergenic Spacer Analysis of Complex Bacterial Communities. Appl Environ. Microbiol. 70, 6147-6156.

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Clarke, K.R., 1993. Non-parametric multivariate analyses of changes in community structure. Aust. J. Ecol. 18, 117–143.

Conradie, W.J., 1994. Vineyard fertilization. Proceedings of a workshop on vineyard fertilization, Nietvoorbij, 30 September, ARC - Fruit, Vine and Wine Research Institute, Private Bag X5026, 7599 Stellenbosch, South Africa.

Curto, G., Dallavalle, E, Lazzeri, L. (2005). Life cycle duriation of Meloidogyne incognita and host status of Brassicaceae and Capparaceae selected for glucosinate content. Nematol. 7, 203-212.

De Caceres, Miquel, Florian Jansen, and Maintainer Miquel De Caceres. "Package ‘indicspecies’." (2015).

Fourie, J.C., Joubert, M. & Freitag, K., 2011. Effect of organic and integrated soil management practices on the weed population in a Pink Lady apple orchard in the Elgin region. SA Fruit Journal February/March, 41-47.

Fourie, JC, Kruger, DHM, Malan, AP., 2015. Effect of management practices applied to cover crops with bio-fumigation properties on cover crop performance and weed control in a vineyard. S. Afr. J. Enol. Vitic. 36, 146-153.

Fourie, J.C., Louw, P.J.E. & Agenbag, G.A., 2001. Effect of seeding date on the performance of grasses and broadleaf species evaluated for cover crop management in two wine grape regions of South Africa. S. Afr. J. Plant Soil 18, 118-127.

Fourie, J.C., Louw, P.J.E. & Agenbag, G.A., 2006. Cover crop management in a Chardonnay/99 Richter vineyard in the Coastal wine grape region, South Africa. 2. Effect of different cover crops and cover crop management practices on grapevine performance. S. Afr. J. Enol. Vitic. 27, 178-186.

Fourie, J.C. & Raath, P.J., 2008. Effect of organic and integrated soil cultivation practices on the weed population in a Sauvignon blanc vineyard situated in the Drakenstein area of the Paarl wine district. Wineland April, 59-63.

Hewson I, Winget DM, Williamson KE, Fuhrman JA, Wommack KE (2006) Viral and bacterial assemblage covariance in oligotrophic waters of the West Florida Shelf (Gulf of Mexico). Journal of the Marine Biological Association of the United Kingdom, 86, 591-603.

Jenkins, W.R., 1964. A rapid centrifugal-flotation technique for seperating nematodes from soil. Pl. Dis. Rep. 48, 692.

Jost, L. (2007). Partitioning diversity into independent alpha and beta components. Ecology, 88, 2427-2439.

Koch, H., Lücker, S., Albertsen, M., Kitzinger, K., Herbold, C., Spieck, E., Nielsen, P.H., Wagner, M. and Daims, H., 2015. Expanded metabolic versatility of ubiquitous nitrite-oxidizing bacteria from the genus Nitrospira. Proceedings of the National Academy of Sciences 112, 11371-11376.

Kleynhans, K.P.N., Van den Berg, E., Swart, A., Marais, M. &Buckley, N.H., 1996. Plant nematodes in South Africa. Handbook no. 8, Plant Protection Research Institute, Pretoria, South Africa.

Kruger, D.H.M, Fourie, J.C, Malan, A.P. (2015) Control Potential of Brassicaceae Cover Crops as Green Manure and their Host Status for Meloidogyne javanica and Criconemoides xenoplax. S. Afr. J. Enol. Vitic. 36, 165-174.

Le Roux, X., Bouskill, N.J., Niboyet, A., Barthes, L., Dijkstra, P., Field, C.B., Hungate, B.A., Lerondelle, C., Pommier, T., Tang, J. and Terada, A., 2016. Predicting the responses of soil nitrite-oxidizers to multi-factorial global change: a trait-based approach. Frontiers in Microbiology, 7.

Levy-Booth, D. J., Prescott, C. E., & Grayston, S. J., 2014. Microbial functional genes involved in nitrogen fixation, nitrification and denitrification in forest ecosystems. Soil Biol. & Biochem. 75, 11-25.

Mardad, I., Serrano, A., & Soukri, A., 2014. Effect of carbon, nitrogen sources and abiotic stress on phosphate solubilization by bacterial strains isolated from a moroccan rock phosphate deposit. J Adv Chem Eng, 1(102), 2.

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Matthiessen, J.N., Warton, B. & Schackleton, M.A., 2004. The importance of plant maceration and water addition in achieving high Brassica-derived isothiocyanate levels in the soil. Agroindustria 3, 277-280.

McLeod, R.W. & Steel, C.C., 1999. Effect of brassica-leaf green manures and crops on the activity and reproduction of Meloidogyne javanica. Nematol. 1, 613-624.

Melakeberhan, H., Xu, A., Kravchenko, A., Mennan, S. & Rika, E., 2006. Potential use of aragula (Eruca sativa L.) as a trap crop for Meloidogyne hapla. Nematol. 8, 793-799.

Miller, R.O., 1998. High temperature oxidation: Dry ashing, Y.P. Kalra (Ed) Handbook of reference methods for plant analysis, pp 53-56. CRC Press, Boca Raton.

Mojtahedi, H., Santo, G.S., Wilson, J.H. & Hang, A.N., 1993. Managing Meloidogyne chitwoodi on potato with rapeseed as green manure. Plant Dis. 77, 42-46.

Navon, A. & Ascher, K.R.S., 2000. Bioassays of entomopathogenic microbes and nematodes. CAB International, Wallingford, UK.

Piedra Buena, A., Garcia-Alvarez, A., Diez-Rojo, M.A. & Bello, A., 2006. Use of cover crop residues for the control of Meloidogyne incocnita under laboratory conditions. Pest Manag. Sci. 62, 919-926.

Rahman, L, Weckert, M. & Orchard, B., 2009. Effect of three consecutive annual applications of brassica green manures on root-knot nematode suppression in soil. Aust. N.Z. Grapegrow. Winemaker 37, 10-12.

Schloss PD, Westcott SL, Ryabin T et al., 2009. Introducing mothur: open-source, platform-independent, community-supported software for describing and comparing microbial communities. Appl Environ. Microbiol 2009;75:7537–7541.

Shapiro, S.S. & Wilk, M.B., 1965. An analysis of variance test for normality (complete samples). Biometrika 52, 591-611.

Slabbert, E., Van Heerden, C.J. & Jacobs, K. (2010). Optimization of Automated Ribosomal Intergenic Spacer (ARISA) for the estimation of microbial diversity in fynbos soil. South African Journal of Science 106: 52-55. DOI:10.4102/sajs/v106i7/8.329

Soil Classification Work Group, 1991. Soil Classification – A Taxonomic system for South Africa. Memoirs on natural agricultural resources of South Africa No. 15, Dept. of Agric. Develop., Private Bag X144, 0001 Pretoria, South Africa.

Statistical Analysis System (SAS), 1990. SAS/STAT users guide, version 8, vol, 2. SAS Institute Inc., Campus Drive, Cary NC.

StatSoft, Inc., 2011. STATISTICA (data analysis software system), version 10. www.statsoft.com. Stirling, G.R. & Stirling, A.M., 2003. The potential of brassica green manure crops for controlling

root-knot nematode (Meloidogyne javanica) on horticultural crops in a subtropical environment. Aust. J. Exp. Agric. 43, 623-630.

The Non-Affiliated Soil Analysis Work Committee, 1990. Handbook of standard soil testing methods for advisory purposes. Soil Sci. Soc. South Africa, P.O. Box 30030, 0132 Sunnyside, South Africa.

Tromp, A. & Conradie, W.J., 1979. An effective scoring system for sensory evaluation of experimental wines. Am. J. Enol. Vitic. 30, 278-283.

Van Coller, GJ. (2004) An investigation of soilborne fungi associated with roots and crowns of nursery grapevines. MSc Thesis, University of Stellenbosch.

Van der Watt, H.V.H., 1966. Improved tables and a simplified procedure for the soil particle size analyses by the hydrometer method. S. Afr. J. Agric. Sci. 9, 911-916.

Walkley, A. & Black, I.A., 1934. An examination of the Degtjareff method for determining organic carbon in soils: Effect of variation in digestion conditions and of inorganic soil constituents. Soil Sci. 63, 251-263.

Whittaker RH (1972) Evolution and measurement of species diversity. Taxon, 21, 213-251.

1. ACCUMULATED OUTPUTS a) TECHNOLOGY DEVELOPED, PRODUCTS AND PATENTS Guidelines for the use of the cover crops and management practices evaluated in the trial are now available and communicated through a variety of technology opportunities.

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b) SUGGESTIONS FOR TECHNOLOGY TRANSFER This has taken place as communicated under publications, papers delivered, as well as lectures and talks given. In the future technology transfer will take place on all levels of the industry on a continuous basis, as done up to date c) HUMAN RESOURCES DEVELOPMENT/TRAINING

Student Name and Surname

Student Nationality Degree (e.g. MSc Agric, MComm)

Level of studies in

final year of project

Graduation date

Total cost to industry throughout the project

Honours students

D. Mashamba South Africa Hons. in Bachelor of Agriculture (Plant production.) Complete September

2013

V. Nyamande South Africa Hons. in Bachelor of Agriculture (Plant production.) Complete September

2013

Masters Students

D. Kruger South Africa MSc. Agric. (Nematology) Complete March 2014

T. Kutama South Africa MSc (Plant Production) Busy writing up the results NA

PhD students

NA

Postdocs

NA

Support Personnel (not a requirement for HORTGRO Science) NA

PERSONS PARTICIPATING IN THE PROJECT (Excluding students)

Initials & Surname

Highest Qualification

Degree/ Diploma registere

d for

Race (1)

Gender (2) Institution & Department Position

(3)

J. Fourie PhD. Agric (Agronomy)

W M ARC Infruitec-Nietvoorbij, Soil Science

PL

A. Malan PhD. Agric (Entomology)

W F US, Dept. of Coservation Ecology & Entomology

Coll

K Jacobs PhD. (Microbiology)

W F US, Dept of Microbiology Coll

F. Halleen PhD. (Plant Pathology)

W M ARC Infruitec-Nietvoorbij, Plant Protection

Co

H Hugo MSc. Agric (Entomology)

W M ARC Infruitec-Nietvoorbij, Plant Protection

Co

E. Kunjeku PhD B F University of Venda, Dept. of Plant Production

Co

C. Ochse MTech (Agric.) W M ARC Infruitec-Nietvoorbij, Soil Science

TA

A. Shubane BTech B F ARC Infruitec-Nietvoorbij, Plant Protection

TA

L. Sassman N6 B M ARC Infruitec-Nietvoorbij, Soil Science

TA

Progress report 88


K. Freitag Grade 12 W F ARC Infruitec-Nietvoorbij, Soil Science

TA

D. Hinds Grade 12 B F ARC Infruitec-Nietvoorbij, Plant Protection

TA

H. Thomas Grade 12 B M ARC Infruitec-Nietvoorbij, Soil Science

TA

C. Vermeulen Grade 12 W F ARC Infruitec-Nietvoorbij, Plant protection

TA

J. Marais Grade 10 W F ARC Infruitec-Nietvoorbij, Plant protection

TA

L. Nel Grade 10 W F ARC Infruitec-Nietvoorbij, Plant protection

TA

(1)Race B = African, Coloured or Indian W = White (2)Gender F = Female M = Male (3)Position Co = Co-worker ( other researcher at your institution) Coll = Collaborator ( participating researcher that does not receive funding for this project from industry) PF = Post-doctoral fellow PL = Project leader RA = Research assistant TA = Technical assistant/ technician

d) PUBLICATIONS (POPULAR, PRESS RELEASES, SEMI-SCIENTIFIC, SCIENTIFIC) Scientific: Kruger, DHM, Fourie, JC, Malan, AP, 2015. The effect of cover crops and the management

thereof on plant-parasitic nematodes in vineyards. S. Afr. J. Enol. Vitic. 36, 195-209. Fourie, JC, Kruger, DHM, Malan, AP, 2015. Effect of management practices applied to cover

crops with bio-fumigation properties on cover crop performance and weed control in a vineyard. S. Afr. J. Enol. Vitic. 36, 146-153.

Kruger, DHM, Fourie, JC, Malan, AP, 2015. Control Potential of Brassicaceae Cover Crops as Green Manure and their Host Status for Meloidogyne javanica and Criconemoides xenoplax. S. Afr. J. Enol. Vitic. 36, 165-174.

Kruger, DHM, Fourie, JC, Malan, AP, 2013. Cover crops with biofumigation properties for the suppression of plant-parasitic nematodes. S. Afr. J. Enol. Vitic. 34, 287-295.

Kruger, DHM, 2013. The role of cover crops with bio-fumigation potential for the suppression of plant-parasitic nematodes in vineyards. Masters dissertation, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa.

Mashamba, D, 2013. Comparison of winter and summer weed species diversity and dry matter production in annual cover crops managed by herbicides in vineyards. Mini-dissertation, University of Venda, Private Bag X5050, 0950 Thohoyando, South Africa.

Nyamande, VR, 2013. Seasonal variation in weed species diversity and dry matter production in cover crops managed by mechanical cultivation in vineyards. Mini-dissertation, University of Venda, Private Bag X5050, 0950 Thohoyando, South Africa.

Semi-scientific: Fourie, JC, Kruger, DHM, Malan, AP, 2016. The performance of cover crops with biofumigation

properties in a drip irrigated vineyard near Stellenbosch. Wineland February, 62-65. Fourie, JC, Malan, AP, Kruger, DHM, 2016. Effect of cover crops and their management on the

ring nematode population in a drip irrigated vineyard. Wineland January, 76-78. Kruger, DHM, Fourie, JC, Malan, AP, 2015. Biofumigation potential of Brassicaceae as a green

manure and their host status for root-knot and ring nematode under controlled conditions. Wineland June, 77-80.

Kruger, DHM, Fourie, JC, Malan, AP, 2014. An overview of the potential of cover crops to suppress plant-parasitic nematodes in grapevine. Wineland, August, 90-94.

Progress report 89


Kruger, DHM, Fourie, JC, Malan, AP, 2014. The role of cover crops with biofumigation potential for the suppression of plant-parasitic nematodes in vineyards. Aspects of Applied Biology 126, 17-18.

e) PRESENTATIONS/PAPERS DELIVERED Papers: Kunjeku, EC, Fourie, JC, 2014. Preliminary evaluation of effectiveness of brassica species as

cover crops in vineyards in Stellenbosch, South Africa. Fifth International Symposium of Biofumigation, Harper Adams University, 9-12 September, Newport, UK.

Kruger, DHM, Fourie, JC, Malan, AP, 2014. The role of cover crops with biofumigation potential for the suppression of plant-parasitic nematodes in vineyards. Fifth International Symposium of Biofumigation, Harper Adams University, 9-12 September, Newport, UK.

Fourie, JC, Sassman, LW, Freitag, K, 2014. Effect of management practices applied to cover crops selected for bio-fumigation on winter growing weeds. Combined Congress, Southern African Weed Science Society, 20-23 January, Grahamstown.

Fourie, JC, Kruger, DHM, Malan, AP, Jacobs, K, Halleen, F, 2013. Effect of cover crops with bio-fumigation potential, and the management thereof, on the nematode and weed population, as well as grapevine performance and soil quality. 35th SASEV Congress, South African Society for Enology and Viticulture, 13-15 November, Somerset West.

Kruger, DHM, Fourie, JC, Malan, AP, 2012. The role of cover crops in suppressing plant-parasitic nematodes in vineyards. 34th SASEV Congress, South African Society for Enology and Viticulture, 14-16 November, Paarl.

Fourie, JC, Sassman, LW, Freitag, K, 2012. The effects of two cover crop management practices applied to cover crops selected for their bio-fumigation potential on winter growing weed stand and spectrum. 34th SASEV Congress, South African Society for Enology and Viticulture, 14-16 November, Paarl.

Halleen, F, Fourie, JC, 2012. The effect of cover crops, selected for their potential to bio-fumigate the soil managed according to two cover crop management practices, on the occurrence of soil-borne pathogens in grapevine roots. 34th SASEV Congress, South African Society for Enology and Viticulture, 14-16 November, Paarl.

Du Toit, A, Slabbert, E, Jacobs, K, Fourie, JC, Du Plessis, K, 2012. Microbial diversity in vineyards under different soil management practices. 34th SASEV Congress, South African Society for Enology and Viticulture, 14-16 November, Paarl.

Kruger, DHM, Fourie, JC, Malan, AP, 2011. The role of cover crops in suppressing plant-parasitic nematodes in vineyards. 2011 Biofumigation & Biopesticide Symposium, 18 October, Sakatoon, Saskatchewan, Canada.

Kruger, DHM, Fourie, JC, Malan, AP, 2011. The role of different cover crops in the suppression of plant parasitic nematodes in South African vineyards: Focus on bio-fumigation potential. 20th Symposium of the Nematological Society of Southern Africa, 18 May, Stellenbosch.

Presentations Kruger, DHM, Fourie, JC, Malan, AP, 2013. The role of different cover crops in the suppression

of nematodes in South African vineyards. Vinpro/WINETECH information day, Lutzville, 23 May.

Kruger, DHM, Fourie, JC, Malan, AP, 2013. The role of different cover crops in the suppression of nematodes in South African vineyards. Vinpro/WINETECH information day, Vredendal, 23 May.

Kruger, DHM, Fourie, JC, Malan, AP, 2013. The role of different cover crops in the suppression of nematodes in South African vineyards. Vinpro/WINETECH information day, Klawer, 22 May.

Kruger, DHM, Fourie, JC, Malan, AP, 2013. The role of cover crops in the suppression of nematodes in vineyards. Specific focus on Brassica crops. Vinpro/WINETECH information day, Montagu, 14 May.

Progress report 90


Kruger, DHM, Fourie, JC, Malan, AP, 2013. The biofumigation concept and preliminary results of MSc study: The role of cover crops in suppressing plant parasitic nematodes in vineyards. Vinpro/WINETECH information day, Malmesbury, 8 May.

Kruger, DHM, Fourie, JC, Malan, AP, 2013. The role of cover crops in the suppression of plant-parasitic nematodes in vineyards. Vinpro/WINETECH information day, Paarl, 18 April.

Fourie, JC, 2013. Cover crop management for sustainable grape production. Bonnievale Agriculture Union meeting, Bonnievale, 17 April.

Fourie, JC, 2013. Cover crop management for sustainable production of wine grapes. Terason cover crop information day, Worcester, 10 April.

Fourie, JC, 2013. The effect of cover crops on the soil, weed control and the performance of perennial crops. Winetech/Vinpro Information Day, 13 February, Hermanus.

Fourie, JC, 2013. The role of cover crops in weed control. Winetech/Vinpro Information Day, 25 January, Paarl.

Fourie, JC, 2012. Effect of cover crops on the nematode and weed population in a Shiraz/101-14 vineyard established on a sandy soil near Stellenbosch. Vinpro/Winetech Information day, Bien Donne Expo, Paarl, 20 April.

Fourie, JC, 2011. Sustainable cover crop management. Regional Information Day, Vinpro, 13 September, Malmesbury.

Fourie, JC, 2011. Weed control and restriction of weed resistance. Landini Elsenburg Farmers Day, Landini and P.W. Agricultural Services, Stellenbosch, 21 July.

2. BUDGET (PHI projects to complete separate Excel annexure)

TOTAL COST SUMMARY OF THE PROJECT

YEAR CFPA DFTS Deciduous SATI Winetech THRIP OTHER TOTAL

2009/10 46 000 351 145 0 365 478 762 623

2010/11 82 320 403 377 201 295 419 841 1 106 833

2011/12 90 550 434 190 217 095 504 528 1 246 363

2012/13 95 075 434 190 217 095 529 755 1 276 115

2013/14 99 829 445 005 0 567 074 1 111 908

TOTAL 413 774 2 067 907 635 485 2 386 676 5 503 842

EVALUATION BY INDUSTRY This section is for office use only

Project number

Project name

Name of Sub-Committee*

Progress report 91


Comments on project

Committee’s recommendation (Review panel in the case of PHI)

• Accepted.

• Accepted provisionally if the sub-committee’s comments are also addressed. Resubmit this final report by___________________________________

• Unacceptable. Must resubmit final report. Chairperson__________________________________________ Date___________________ *SUB-COMMITTEES Winetech Viticulture: Cultivation; Soil Science; Plant Biotechnology; Plant Protection; Plant Improvement; Oenology: Vinification Technology; Bottling, Packaging and Distribution; Environmental Impact; Brandy and Distilling; Microbiology Deciduous Fruit Technical Advisory Committees: Post-Harvest; Crop Production; Crop Protection; Technology Transfer Peer Work Groups: Post-Harvest; Horticulture; Soil Science; Breeding and Evaluation; Pathology; Entomology

Documents

FINAL REPORT - SAWIS libraryResearcher surname 4 This document is confidential and any unauthorised disclosure is prohibited Version 2015 4. Determine the effect of the different treatments