Exploring the effects of seed size and target plant densities on the yield of hybrid canola across AustraliaJustin Kudnig, Pacific Seeds

Key words: canola, varieties, hybrid, triazine tolerant (TT), Roundup Ready (RR), Clearfield + triazine tolerant (CT), cultivar type, seed size, plant populations, seed-lots, plant height, grain yield.

Key messages

Genetics x Environment x Management interactions are very complex and dynamic. Genetics (G) is the most controllable factor, more specifically for pre-planting, i.e. varietal choice, while Environment (E) is by far the most significant factor. Management (M) will influence yield to a small degree in some environments, but for every environment where M has a significant effect, there are many environments where it will not. From a crop management perspective, the main consideration is time spent, logistics and associated costs versus return.

There was a trend for the RR hybrid with smaller seed size to generate population densities lower than targeted. There was a similar but less consistent trend for the TT and CT technologies with smaller seed size to generate lower population densities. However, we did not observe a statistically significant effect of seed size on plant count and the percentage of plants established relative to populations targeted varied substantially across different seed lots and environments.

All four hybrid-seed lots with larger seed sizes generated more observed biomass at the 4-6 leaf stage. All hybrids with higher target treatments for plant population finished flowering and pod maturity two to four days earlier and plant height was observed as slightly lower, however this was not significant. This may provide benefits in terms of enhancing crop competitiveness against weeds in addition to reducing risk of high temperatures and/or frosting during flowering and early seed-fill stages.

Despite a large range in seed size the grain yield (t/ha) of hybrids was not significantly different across environments or plant population treatments. However, there was a few individual environments where significant differences in grain yield (t/ha) were observed between hybrids with seed ranging from 4.54 to 8.92 grams per 1,000 seeds (equivalent to seed counts of 112,000 to 220,000 seeds per kilogram) within different plant population treatments.

Aims

To determine differences in plant establishment (plants/m2), visual (subjective) plant vigour or biomass, windrowing maturity, plant height (cm) and grain yield (t/ha) production of four different hybrids across 11 different canola growing environments in Australia.

The 11 trial environments differed widely in seasonal rainfall, cropping history, soil type, soil pH, water holding capacity. Best management practices and district standard practice treatments were applied per each location.

Introduction

Previous research is conflicted regarding the impact of canola seed size, especially in hybrids, on percentage establishment, especially from depth.

Brill et al (2015) demonstrated that deep-sown hybrid cultivars with larger seed maintained higher emergence rates and grain yield than open-pollinated cultivars. They also showed that larger seed size of both hybrid and open-pollinated canola increased early biomass accumulation and final grain yield.

However, Harries & Seymour (2018) found that seed size did not significantly affect canola emergence, yield or seed quality. While an increasing seed size had a positive linear association with early canola biomass and 1000-seed weight, both days-to-flowering and days to the end of flowering had a negative linear association with seed size.

French et al (2016) carried out 24 experiments across a range of agricultural environments in Western Australia between 2010 and 2014 canola (Brassica napus L.). They found the response of grain yield to crop density could be adequately described by an asymptotic model (where yield approaches but never quite reaches a ceiling at very high density).

Zhang et al (2016) demonstrated that the relative yield and profit of Australian canola hybrids compared to open-pollinated canola was largely determined by growing-season rainfall.

This paper outlines the results of canola seed-lot trials carried out in 2019 across a more diverse range of Australian environments than previous studies. The aim was to determine the relative importance of canola seed size on plant population density and seed yield using various hybrids containing different genetic backgrounds and herbicide technologies.

Method

Eleven field research extension trials using randomised complete block design with three replicates were sown across Australia with the individual locations at Kellerberrin WA, York WA, Gnowangerup WA, Wagin WA, Kojonup WA, Nyabing WA, Beulah Vic, Lake Bolac Vic, Greenethorpe NSW, Ardlethan NSW and Lockhart NSW.

Four canola varieties of differing maturity within three different herbicide technology groups and with three different target populations were compared. Herbicide technologies included: CT - Clearfield® + Triazine Tolerant, Triazine Tolerant and Roundup Ready®. Varieties included: a 3-series early TT Hybrid, a 4-series early-mid RR Hybrid, a 5- series mid-early TT Hybrid and a 5-series mid CT hybrid.

Target population treatments included: 15 plants per m2, 25 plants per m2 and 40 plants per m2 based on an estimated 65% establishment survival factorial by adjusting all seed packet weights.

Table 1. Details of the 2019 plant population by seed size hybrid trialsTrial Trial Trial Design Sowing GSR (mm) Trial Mean

Location State Purpose # Reps Date Rainfall Yield (t/ha)

York WA RR – Pop*Size RCB 3 21.05.2019  304  2.02 

Kojonup WA RR – Pop*Size RCB 3 14.05.2019  280 1.17 

Lake Bolac VIC RR – Pop*Size RCB 3 15.05.2019   385 2.38 

Greenethorpe NSW RR – Pop*Size RCB 3 06.05.2019   135 0.58 

Gnowangerup WA CT/TT – Pop*Size RCB 3 18.05.2019   254 1.04 

Nyabing WA CT/TT – Pop*Size RCB 3 14.05.2019   240 1.54 

Kellerberrin WA CT/TT – Pop*Size RCB 3 02.05.2019  183 1.01

Wagin WA CT/TT – Pop*Size RCB 3 14.05.2019  280 1.68 

Lockhart NSW CT/TT – Pop*Size RCB 3 06.05.2019   233 0.67 

Ardlethan NSW CT/TT – Pop*Size RCB 3 24.04.2019   185 0.49 

Beulah VIC CT/TT – Pop*Size RCB 3 29.04.2019   260 1.75 

Table 2. 2019 Hyola 404RR treatment and quality details

Treatment Numbers

Treatment Name

Seed Count (seeds/kg)

PopulationTargets

Germination %

Seed Vigor %

TSW(g)* & seed size

(mm)

1,2,3 Hyola 404RR-154 154,000 15,25,40 p/m2 99% 98% 6.49 2.0-2.2mm

4,5,6 Hyola 404RR-181 181,000 15,25,40 p/m2 98% 94% 5.52 2mm

7,8,9 Hyola 404RR-196 196,000 15,25,40 p/m2 96% 92% 5.10 2mm

10,11,12 Hyola 404RR-213 213,000 15,25,40 p/m2 94% 90% 4.69 1.8<2mm

*TSW = target seed weight

Table 3. 2019 Hyola 350TT, Hyola 559TT, Hyola 580CT treatments and quality details

Treatment Numbers

Treatment Name

Seed Count (seeds/kg)

Population Targets

Germination %

Seed Vigor %

TSW(g)* & Seed Size

(mm)

1,2,3 Hyola 350TT-112 112,000 15,25, 40 p/m2 98% 98% 8.92 >2.2mm

4,5,6 Hyola 350TT-130 130,000 15,25, 40 p/m2 96% 95% 7.69 >2.2mm

7,8,9 Hyola 350TT-155 155,000 15,25, 40 p/m2 98% 95% 6.45 2.0-2.2mm

10,11,12 Hyola 559TT-150 150,000 15,25, 40 p/m2 97% 95% 6.66 2.0-2.2mm

13,14,15 Hyola 559TT-180 180,000 15,25, 40 p/m2 99% 97% 5.55 2mm

16,17,18 Hyola 559TT-213 213,000 15,25, 40 p/m2 92% 90% 4.69 1.8<2mm

19,20,21 Hyola 580CT-206 206,000 15,25, 40 p/m2 94% 93% 4.85 1.8<2mm

22,23,24 Hyola 580CT-220 220,000 15,25, 40 p/m2 91% 90% 4.54 1.8<2mm

*TSW = target seed weight

Measurements done were plants per m2 using 4x1m row counts per plot 14 days after sowing and 28 days after sowing, visual subjective vigour ratings at the 4-6 leaf stage, visual maturity ratings at flowering and maturity, plant height in (cm) at 5cm intervals, grain yield (t/ha) using plot harvesters and oil % content using nuclear magnetic resonance spectroscopy.

Results and Discussion

French et al (2016) showed that field establishment varied from 0.3 to 1 (where 0.3 = 30% and 1 = 100%) and was higher at low target densities with a median of 0.585 at a target density of 40 plants/m². Our research showed whilst specifically referencing two hybrids, that final field establishment varied from 30% to 118% for Hyola 404RR and 23% to 133% for Hyola 559TT (Figures 1 and 2). Where the final establishment values were higher than 100% are most likely to have been a function of the pre-plant field establishment factorial used of 65%. Example calculation for the treatment Hyola 404RR-213 with Target = 15 plants/m2, Germination = 94%, Est Factorial = 65% and seeds sown = 25 per m2, [(25*0.94)*0.65)] = 15 plants per m2 where the maximum possible establishment from this seedlot is actually [(25*0.95)*1.0)] = 24 plants per m2 (156% of target).

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Hyola® 404RR - Mean % of target population achieved by treatment across four environments

Figure 1. Hyola 404RR: mean proportion (%) of target population achieved by seed size treatment across four environments.

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Hyola® 559TT - Mean % of Target Population Achieved by Treatment across 7 Environments

Figure 2. Hyola 559TT: mean proportion (%) of target population achieved by seed size treatment across four environments.

French et al (2016) demonstrated that there was little difference between optimum densities for hybrid and open-pollinated cultivars, with the optimal density in the high rainfall zone about 10 plants/m² higher than in low and medium rainfall zones.

Our research demonstrates that site environmental conditions, variety and seed-lot source had larger effects on final established % of plant numbers than seed size and target plant populations. Specifically related to seed-lot source, we anticipate that not every seedlot of any 'particular variety' with the same seed size/count may potentially have the same seed vigour or establishment growth behaviour.

Table 4. Hyola 404RR: treatment mean plant maturity (series) and plant height (cm)

Treatment Description Mean Plant Maturity Series Mean Plant Height (cm)

Hyola 404RR-154-15 4.68 140Hyola 404RR-154-25 4.25 138Hyola 404RR-154-40 4.13 138Hyola 404RR-181-15 4.58 140Hyola 404RR-181-25 4.18 140Hyola 404RR-181-40 4.00 138Hyola 404RR-196-15 4.45 139Hyola 404RR-196-25 4.43 138Hyola 404RR-196-40 4.05 134Hyola 404RR-213-15 4.50 137Hyola 404RR-213-25 4.23 140Hyola 404RR-213-40 3.83 134

Table 4 shows that with Hyola 404RR, across all environments, there was a decrease in plant maturity within each seed size and when moving from lower to higher populations, however this was not always significant within individual environments. In most environments there was a decrease in mean plant height (2-4cm) with higher populations with only small differences in plant height when comparing between seed sizes (which were not significant).

Table 5. Hyola 350TT, Hyola 559TT and Hyola 580CT: treatment mean plant maturity (series) and plant height (cm).

Treatment Description Mean Plant Maturity Series Mean Plant Height (cm)

Hyola 350TT-112-15 3.94 128Hyola 350TT-112-25 3.78 126Hyola 350TT-112-40 3.59 125Hyola 350TT-130-15 3.71 124Hyola 350TT-130-25 3.66 124Hyola 350TT-130-40 3.46 120Hyola 350TT-155-15 3.61 124Hyola 350TT-155-25 3.55 123Hyola 350TT-155-40 3.34 120Hyola 559TT-150-15 4.66 133Hyola 559TT-150-25 4.71 131Hyola 559TT-150-40 4.43 129Hyola 559TT-180-15 4.97 129Hyola 559TT-180-25 4.84 127Hyola 559TT-180-40 4.79 123Hyola 559TT-213-15 4.95 128Hyola 559TT-213-25 5.00 129Hyola 559TT-213-40 4.91 125Hyola 580CT-206-15 5.11 132Hyola 580CT-206-25 4.86 131Hyola 580CT-206-40 4.75 127Hyola 580CT-220-15 5.04 131Hyola 580CT-220-25 5.14 133Hyola 580CT-220-40 4.91 128

Table 5 shows with Hyola 350TT, Hyola 559TT and Hyola 580CT there was no consistent relationship between plant maturity and seed size or population density across environments.

In most environments there was a small decrease in mean plant height (3-6cm) with higher population treatments and only small differences in plant height when between seed size treatments (which were found not to be significant).

Yield responses across the 11 trial environments varied between varieties, seed sizes and plant population targets. Previous research studies have also shown mixed outcomes relating to the effect of seed size and plant densities on grain yield.

Catalier (2019) found in some studies, canola yield increased with seeding rate (Harker et al 2012a), while in other studies seeding rate did not influence yield (Kutcher et al 2013).

Gan et al (2016) observed that yield response to seeding rate appeared to depend not only on environment, but also on what seeding rates or plant densities were being compared.

Yang et al (2014) found that seed yield increased with seeding rate, however leveled off at higher plant densities. In regards to seed size, yield benefit from larger canola seed was observed by Elliot et al (2008) and Brill et al (2016), while Harker et al (2015), Clayton et al (2009), and Lamb and Johnson (2004) did not measure a benefit of larger seed on canola yield.

Table 6. Hyola 404RR: grain yield (t/ha) responses to four seed sizes and three target plant populations across four environments in Australia

Location Greenethorpe NSW Kojonup

WA Lake Bolac VIC York

WA

Treatment Yield t/ha sig Yield t/ha sig Yield t/ha sig Yield t/ha sig

Hyola 404RR-154-15 0.57 ab 1.10 ab 2.25 b 2.08 a

Hyola 404RR-154-25 0.62 a 1.15 ab 2.75 a 2.05 a

Hyola 404RR-154-40 0.63 a 1.35 a 2.46 ab 2.10 a

Hyola 404RR-181-15 0.58 ab 1.19 ab 2.14 b 1.88 a

Hyola 404RR-181-25 0.60 ab 1.25 ab 2.37 b 2.20 a

Hyola 404RR-181-40 0.63 a 1.24 ab 2.28 b 2.20 a

Hyola 404RR-196-15 0.50 b 0.97 b 2.35 b 1.91 a

Hyola 404RR-196-25 0.54 ab 1.21 ab 2.29 b 1.99 a

Hyola 404RR-196-40 0.59 ab 1.18 ab 2.49 ab 1.97 a

Hyola 404RR-213-15 0.57 ab 1.13 ab 2.43 ab 1.90 a

Hyola 404RR-213-25 0.61 a 1.24 ab 2.45 ab 2.06 a

Hyola 404RR-213-40 0.59 ab 0.99 b 2.30 b 1.87 a

Raw Mean 0.59 1.17 2.38 2.02 CV 11.05 15.98 9.16 10.67

LSD (P=0.05) 0.11 0.31 0.35 0.36

Gnowangerup WA Kellerberrin WA Nyabing WA Wagin WA0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.252019 Hyola 350TT - Analysed Grain Yield (t/ha) by WA Location by Seed Size by Target Population

Hyola 350TT-112-15 Hyola 350TT-112-25 Hyola 350TT-112-40 Hyola 350TT-130-15Hyola 350TT-130-25 Hyola 350TT-130-40 Hyola 350TT-155-15 Hyola 350TT-155-25Hyola 350TT-155-40

Figure 3. Hyola 350TT: grain yield (t/ha) responses to four seed sizes and three target plant populations across four Western Australian environments

Gnowangerup WA Kellerberrin WA Nyabing WA Wagin WA0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.252019 Hyola 559TT - Analysed Grain Yield (t/ha) by WA Location by Seed Size by Target Population

Hyola 559TT-150-15 Hyola 559TT-150-25 Hyola 559TT-150-40 Hyola 559TT-180-15Hyola 559TT-180-25 Hyola 559TT-180-40 Hyola 559TT-213-15 Hyola 559TT-213-25Hyola 559TT-213-40

Figure 4. Hyola 559TT: grain yield (t/ha) responses to four seed sizes and three target plant populations across four Western Australian environments.

Gnowangerup WA Kellerberrin WA Nyabing WA Wagin WA0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.252019 Hyola 580CT - Analysed Grain Yield (t/ha) by WA Location by Seed Size by Target Population

Hyola 580CT-206-15 Hyola 580CT-206-25 Hyola 580CT-206-40 Hyola 580CT-220-15Hyola 580CT-220-25 Hyola 580CT-220-40

Figure 5. Hyola 580CT: grain yield (t/ha) responses to four seed sizes and three target plant populations across four Western Australian environments.

This paper has only shown the yield results from Western Australian trials for the CT and TT hybrids, however the Eastern Australian States trials showed similar relationships. Often there is little or no significant yield responses in RR, TT or CT hybrids with different seed sizes and plant population targets across all the testing environments.

As highlighted with all the 2019 individual trial results, hybrid genetic background and associated adaptability along with strong environmental influences (rainfall frequency and amounts, soil type, frost events, time of sowing) played a more substantial role or influence on the final yield responses than did seed size or actual plant population.

Conclusion

This study highlights that a canola ‘seed size range’ that optimises canola emergence and grain yield potentially exists (TSW 6.5g to 5.0g ≈ 150,000 to 190,000 seeds/kg) and that larger seed has been found to provide higher observed biomass accumulation and % establishment in some environments. However, G X E interactions often override (M) management decisions based around seed size, population targets and their resultant grain yields.

Seed size does impact the percentage of plants both emerged and established to varying levels in different environments, and larger seed at lower plant populations leads to final plant maturity being delayed. Higher plant populations irrespective of seed size and variety genetics often showed decreased observed maturity and sometimes plant height.

In 2020, Pacific Seeds will continue this important industry research by focusing the evaluation on the relationships between TT and CT hybrids vs 3 OP TT varieties (actual farmer prepared retained samples) at different plant populations and seed sizes. This research will help growers and advisors have more information around determining any potential grain yield and gross return $/ha value of grading OP TT varieties to larger seed sizes and planting at higher rates versus high yielding TT and CT hybrids.

Acknowledgments2019 Trial Development, design and analysis by Dr David Tabah, Crop Research Lead (Canola), Advanta Seeds

2019 Trial planting, maintenance, spraying and harvest across Australia by Kalyx Australia, Living Farms and TrialCo

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Brill RD, Jenkins L, Gardner M (2014) Canola establishment; does size matter? In ‘Grains Research and Development Corporation Advisor Update.

Catellier C, (2019) M.Sc. P.Ag., Research Associate Optimal Seeding rate based on seed size in canola. Project #Carp SCDC 20 18-084, The Saskatchewan Canola Development Commission.

French RJ, Seymour M, Malik RS (2016) Plant density response and optimum crop densities for canola (Brassica napus L.) in Western Australia. Crop & Pasture Science 67, 397–408.

Gan Yantai, a K. Neil Harker, b H. Randy Kutcher, c Robert H. Gulden, d Byron Irvine, e William E. May, f John T. O'Donovanb, (2016) Canola seed yield and phenological responses to plant density, Canadian Journal of Plant Science 96(1): 151-159

Hanson BK, Johnson BL, Henson RA, Riverland NR (2008) Seeding rate, seeding depth, and cultivar influence on spring canola performance in the Northern Great Plains. Agronomy Journal 100, 1339–1346.

Harker KN, O’Donovan JT, Smith EG, Johnson EN, Peng G, Willenborg CJ, Gulden RH, Mohr R, Gill KS, Grenkow LA (2015) Seed size and seeding rate effects on canola emergence, development, yield and seed weight. Canadian Journal of Plant Science 95, 1–8.

Kutcher HR,1 T. K. Turkington,2 G. W. Clayton,3 K. N. Harker2 (2013) Response of herbicide-tolerant canola (Brassica napus L.) cultivars to four row spacings and three seeding rates in a no-till production system. Canadian Journal of Plant Science, 2013, 93(6): 1229-1236

Zhang H, Berger JD, Milroy SP (2013) Genotype × environment interaction studies highlight the role of phenology in specific adaptation of canola (Brassica napus) to contrasting Mediterranean climates. Field Crops Research 144, 77–88.

Zhang H, Berger JD, Seymour M, Brill R, Herrmann C, Quinlan R, Knell G (2016) Relative yield and profit of Australian hybrid compared with open-pollinated canola is largely determined by growing-season rainfall. Crop & Pasture Science 67, 323–331.

Paper reviewed by

Dr David Tabah, Crop Research Lead (Canola) – Advanta Seeds Australia