Dual-purpose use ofwinter wheat inwestern China: cuttingtime and nitrogen application effects on phenology, forageproduction, and grain yield

L. H. TianA,B, L. W. BellC, Y. Y. ShenA,B,D, and J. P. M. WhishC

AThe State Key Laboratory of Grassland Agro-ecosystems, Lanzhou 730020, China.BCollege of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China.CCSIRO Ecosystems Sciences/APSRU, PO Box 102, Toowoomba, Qld 4350, Australia.DCorresponding author. Email: yy.shen@lzu.edu.cn

Abstract. Conventional rainfed mixed crop–livestock systems of western China lack high-quality forage and restrictlivestock production. This study explored the forage potential from wheat and its effects on subsequent grain yield.Different cutting times were imposed on winter wheat (Triticum aestivum) at Qingyang, Gansu Province, in two growingseasons, and the effect of nitrogen (N) topdressing rates (0, 60, and 120 kgN/ha) on grain yield recovery was explored.Results showed the potential to produce 0.8–1.6 t DM/ha of wheat forage with high nutritive value when cut before stemelongation (GS 30). In the wetter year, cutting before stem elongation did not delay crop development significantly(<3 days at anthesis and 5 days at maturity), but grain yields were reduced by 17–28% compared with the uncut crop(5.8 t DM/ha), mainly due to reductions in number of spikes per m2 and, consequently, number of grains per m2. In bothseasons, more forage biomass was available if crops were cut later than GS 32, but this camewith large reductions (>62%)in grain yield and delays in crop development (>9 days or 131 degree-days). Crops cut later thanGS 30 had greatly reducedharvest index, tillers per m2, and total N uptake but higher grain protein content. There was no significant effect of Ntopdressing rate on grain yield, although provided the crop was cut before GS 30, higher rates of N increased maturitybiomass and crop N uptake by replacing N removed in cut biomass. This study showed that physiological delay of wheatdue to cuttingwas not significant. The forage harvested fromwinter wheat before stem elongation could be a valuable feedresource to fill the feed gap in western China.

Additional keywords: defoliation, kernels, phenology, nitrogen.

Received 20 March 2012, accepted 20 July 2012, published online 18 September 2012

Introduction

The dual-purpose use of wheat crops for grazing during theirvegetative phase and allowing the crop to regrow to harvest grainis practiced in many countries including Argentina, Morocco,Pakistan, Syria,Uruguay,Australia, andMediterranean countries(Rodríguez et al. 1990; Francia et al. 2006). In particular, wheatforage has historically played an important role in agriculturalproduction areas of the SouthernGreat Plains in theUnitedStates,with at least 2.4Mha, 50% of the wheat-planting area, used fordual-purpose (Pinchak et al. 1996). Grazing of cereals has alsobeen effective for filling feed gaps in mixed farming systems inAustralia (Moore 2009). Dual-purpose crops are an attractivemanagement option for farmers because the forage is of highnutrition, which is conducive to livestockweight gain, it providesan alternative source of feed during a feed gap period, thereduced stubble load can benefit the sowing operation of thefollowing crop, and the dual incomes from grain and livestockimprove farmprofit comparedwith a grain-only system (Harrisonet al. 2011a).

Various studies around the world have shown that wheatcan be grazed without reducing grain yield (Holliday 1956;Christiansen et al. 1989; Redmon et al. 1995). To this end,Harrison et al. (2011a) report from their review of 276 dual-purpose crop experiments that defoliation has a positive effecton grain yield (7� 25%); however, the timing of the defoliationis critical and more important than the rate or type of defoliation(including clipping, crash, or long-term rotational grazing)in achieving this increase. Removing livestock before thedevelopment of the first hollow stem (GS 31) (Zadoks et al.1974) reduces the likelihood of grain yield losses comparedwith ungrazed crops (Harrison et al. 2011a). If grazing isextended past this critical time, then larger grain yieldreductions occur (Redmon et al. 1996; Virgona et al. 2006).The main reason for this yield reduction is removal of the cropgrowing points (Sprague 1954; Pumphrey 1970). Alternatively,under certain conditions, grazing can increase grain yield byreducing lodging in tall varieties (Christiansen et al. 1989;Winterand Musick 1991) or by reducing crop leaf area and water

Journal compilation � CSIRO 2012 www.publish.csiro.au/journals/cp

CSIRO PUBLISHING

Crop & Pasture Science, 2012, 63, 520–528http://dx.doi.org/10.1071/CP12101

use during vegetative growth, thereby conserving soil wateruntil after flowering when crops convert water used to grainyield with higher efficiency (Virgona et al. 2006; Harrison et al.2010).

The impact of different defoliation methods on grain yield isconsidered minimal, with comparisons between grazing andclipping showing the methods are comparable (Dann 1968;Dann et al. 1977; Francia et al. 2006). More studies find thatgrain yield increases occurred when grazing was used as thedefoliation method; however, this may be a result of theheterogeneous nature of animal defoliation compared withthe uniform nature of mechanical clipping or mowing(Virgona et al. 2006; Harrison et al. 2011a).

Nitrogen (N) availability may also play an important role inassisting crop regrowth after defoliation. Removal of vegetativeplant growth during cutting or grazing removes accumulatedcrop N and, hence, could induce N stress during grain yieldrecovery. It is common practice to provide supplementary Nfertiliser after grazing; however, Virgona et al. (2006) showedthat N fertiliser uptake was not increased after grazing, whichsuggests that in some situations there is poor recovery of fertiliserapplied after defoliation. The impact of N application on croprecovery and uptake after defoliation in north-west China hasnot been explored.

Increasing livestock production on small-holder farms innorth-west China has the potential to improve the livelihoodsof the rural poor in this region (Komarek et al. 2012).Livestock are primarily pen-fed with crop residues (wheat,maize, and millet) and lucerne, which is cut and carried (Houet al. 2008). However, the expansion of livestock productionin mixed farms has been limited by a large feed gap in latewinter and early spring (January–May) because foragesources such as crop stubbles and pasture residues are inshort supply and of low quality (Hou et al. 2008). This greatlyrestricts farmers’ incomes and subsequent increase indevelopment of a regional livestock industry. Meanwhile,winter wheat is the main rainfed grain crop in the region,with a planting area of 13Mha, accounting for half of the totalwinter wheat grain yield of the Gansu Province. This potentialfeed resource is rarely used as forage for livestock. In order tohelp address the feed gap, we explored the potential of usingwinter wheat as a forage source. Two experiments over twogrowing seasons examined the quantity and quality ofavailable green wheat forage at various times and theconsequent effect on grain yield and quality. The effect ofN topdressing for improving crop recovery after cutting andreducing potential grain reductions was explored in thesecond experiment. This is the first study we are aware ofinvestigating the feasibility of cutting wheat for livestockfeeding in the rain-fed region of western China.

Materials and methodsExperimental site description and conditions

Experiments were established at Qingyang Loess PlateauResearch Station of Lanzhou University (358400N, 1078520E;altitude 1298m a.s.l.), at Shishe, Qingyang City, in GansuProvince of China. Agriculture in this area of the westernLoess Plateau is rainfed with summer-dominant rainfall (91%of rain falls between April and October) and a cold semi-aridclimate (BSk in the Köppen climate classification, Peel et al.2007). Average annual precipitation at Shishe is 561mm,with anaverage of 255 frost-free days. On average, 339mm falls in thewheat growing season (September–July), and the summerfallow during the wetter months (August–September) is usedto refill the soil profile before next sowing. The soil is classifiedas Heilu (Zhu et al. 1983), a very deep loess silt-loam with aplant-available water-holding capacity of 419mm to a depth of3m, a uniform profile with a surface (0–200mm) pH of 8.2,organic carbon content 6.8 g kg–1, total N 0.84 g kg–1, and bulkdensity 1.24 g cm–3. Daily rainfall, solar radiation, and airtemperature were recorded using the automatic weather stationon site.

The two experimental seasons were conducted undercontrasting growing conditions (Table 1). Total precipitationduring the 2008–09 wheat growing season was 226mm(September to July of the following year), 111mm below thelong-term average over this period, with monthly precipitationless than average in 8 of the 10 months. Plant available soil waterat sowing measured to a depth of 2.5m was 74mm and the totalcrop water use was estimated to be 277mm (evapotranspiration,drainage, and runoff were assumed negligible here). In contrast,the growing season rainfall of the 2009–10 season was 406mm,69mm above the long-term average. Only 4 of 10 monthshad lower monthly rainfall than the long-term average. Plantavailable soil water at sowing was 299mm and total crop wateruse was estimated to be 696mm.

Cutting treatments

Experiment 1. 2008–09

Three cutting times imposed in the spring of the 2008–09season [15 April (GS 32), 3 May (GS 52), 17 May (GS 61)]were compared with an uncut control. These cutting treatmentswere designed to investigate trade-offs between biomassproduction and subsequent grain yield; however, phenologicalstages at these cutting times were later than anticipated due to therapid crop development in this year. Crops in cutting treatmentswere cut once at ground level using hand shears and all plantmaterial was removed, following traditional harvesting methodsused in other forage crops. Treatments were arranged in a

Table 1. Precipitation (mm) for each month of two consecutive cropping seasons (September–June), and the long-term average precipitation(1961–2008) at Qingyang, China (mm)

Season Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June Growing season

2008–09 93 13 3 0 2 14 11 10 49 34 2292009–10 34 14 32 0 17 10 97 116 39 47 406Long-term av. 90 42 17 4 4 7 19 38 53 65 339

Dual-purpose use of winter wheat in China Crop & Pasture Science 521

randomised complete block design with five replicates, and thearea of each plot was 3m by 3m.

Experiment 2. 2009–10

Six cutting times were imposed in the 2009–10 season, twobefore the winter dormant period (21 October and 9 December2009) and four during spring regrowth (21 March, 5 April, 20April, 5 May 2010); all were compared with an uncut control.Each treatment was cut by hand following the same procedureas in Expt 1. Cutting times during spring were earlier than in the2008–09 season as results from the previous year showed thatlater cutting had a large impact on subsequent crop growth andyield. The effect of different levels of N fertilisation was includedas a factor in the 2009–10 season to test whether recovery growthand grain yield after cutting were improved with added Nnutrition. Three N topdressing treatments (N0, 0 kgN ha–1; N60,60 kgN ha–1; N120, 120 kgN ha–1) were applied as urea at stemelongation of the uncut crop (21 April 2010). The experimentwas arranged in a split-plot design with three replicates; themain plot was N application treatment and the subplot wascutting time.

Crop management

Wheat (Triticum aestivum) was sown under conventional tillageon 7 September 2008 (cv. Xifeng 19) and 15 September 2009 (cv.Longyu 216) at a seeding rate of 187 kg ha–1 (consistent withfarmer practice in this region) with 0.15-m row spacing; theestablished crop density was ~200 plantsm�2. The two varietiesused in the two growing seasons varied in phenological maturityby 7 days; Xifeng 19, used in 2008–09, is 294 days to maturity(2234 degree-days) and Longyu 216, used in 2009–10, is287 days (1963 degree-days). In the 2008–09 season,660 kg ha–1 of organic manure fertiliser was applied at sowing,and urea was topdressed at a rate of 187.5 kg ha–1 in April 2009.In the 2009–10 season, organic manure fertiliser was applied at600 kg ha–1 at sowing (different topdressing rates of N wereincluded as experimental treatments).

Forage quality and crop N uptake

Nitrogen content of the forage biomass at each cutting time, andof grain and stover at maturity, were measured separately usingthe Kjeldahl determination. Neutral-detergent fibre (NDF) andacid-detergent fibre (ADF) of the forage biomass were analysedby agitating samples in boiling neutral/acid detergent solutionfor 1 h anddetermining the drymatter loss (VanSoest et al. 1991).Ash content was measured after igniting samples in furnace at5508C for 3 h. All samples were ground and homogenised beforeanalysis. Crude protein was estimated from N content multipliedby 6.25. Total crop N uptake was calculated as the sum of the Nconcentration of plant components multiplied by its contributionto total plant biomassof each component (i.e.N in forage removedat cutting and N in grain and biomass at final harvest).

Crop phenology, growth and yield

Crop phenological development was observed every 2 weeks onfive randomly selected plants in each plot after the first cuttingwas imposed, following the method described by Zadoks et al.(1974). Accumulated thermal time was calculated over periodsbetween key crop phenological stages using three cardinal

temperatures, base (08C), optimum (288C), and maximum(358C), to calculate daily thermal time (in degree-days) for3-hourly air temperatures interpolated from daily maximumand minimum temperatures. The effect of altered phenologydue to cutting on the growing conditions pre-heading wasinvestigated by calculating the average photo-thermal quotientover the 30 days before anthesis, i.e. the ratio of daily radiation(MJm–2) to daily thermal time accumulated (degree-days)(Ortiz-Monasterio et al. 1994).

Crop biomass at each cutting time, final grain yield, andmaturity biomass were measured by cutting six rows of 1mlength (i.e. 0.9m2) from the plot centre at ground level.Biomass was dried at 808C for 48 h, while grain was dried at368C for 48 h. In the 2009–10 season, crop height and number ofspikes perm2 atfinal harvestwere recorded andyield componentsincluding grain weight per spike and number of grains per spikewere measured from five grab samples. Kernel weight for 1000grains was measured and harvest index calculated as the ratio ofgrain yield to total maturity biomass.

Statistical analyses

Statistical analyses were conducted for each experimental yearusing an ANOVA in GENSTAT Release 13 (Lawes AgriculturalTrust, Rothamsted Experimental Station, Oxford, UK).Differences were compared using l.s.d. at P = 0.05.

Results

Forage biomass and quality at cutting

In both experimental seasons, the later cut treatments generatedprogressively more forage biomass for dual-purpose use. Inthe drier first experimental year, 1.2 t DMha–1 of forage washarvested at the first cutting time (GS 32); delaying cutting for afurther 28 days produced an additional 0.8 t DMha–1 (Table 2). Inthe second experimental year, more biomass was available atthe same crop phenological stage (i.e. 2.3 t DMha–1 at GS 32 on20 April 2010) (Table 3). Up to 1.3 t DMha–1 was produced inautumn before the winter dormant period, and 1.6 t DMha–1 ofbiomass was available before stem elongation (i.e. GS 30) thefollowing spring (Table 3).

Forage quality was highest and similar for all cutting timesbefore stem elongation (GS 30), with a high crude protein content(20.2–24.9%), average NDF of 519 g kg–1 and average ADF of306 g kg–1 (Table 3). Once cutting was delayed beyond stemelongation, forage quality declined; with crude protein decliningby 3.4–4.8% by booting and further still by flowering(Tables 2 and 3). Fibre content generally increased once thecrophad reachedbooting, but the trendwas less clear.Ash contentalso seemed todecline inbiomassharvested after stemelongation.There was no significant difference in forage quality or yieldbetween N topdressing treatments, since all of these treatmentswere imposed at stem elongation stage.

Crop phenology

In the first experimental year (2008–09), later cutting timesincreased the delays in crop phenology, with the main delayoccurring in the period up to early booting (GS 41), after whichthermal time accumulation was the same as the uncut control.Cutting at GS 32 delayed crop early flowering and maturity by

522 Crop & Pasture Science L. H. Tian et al.

10 days and accumulated thermal time units to key phenologicalstages increased by 129–217 degree-days (Table 4). With thelater cutting times, the additional phenological delay was smallerthan the interval between cutting times. For example, start offloweringwas only delayed by an additional 25 and 33 dayswhencut 28 and 42 days later. When cut later than GS 32, the periodand accumulated thermal time to start of flowering was delayedmore than the period to crop maturity, and so the grain-fillingperiod in these treatments was reduced by 9–13 days. Thephoto-thermal quotient (PTQ) pre-heading of the uncut crop(1.41MJm–2 day–1 8C–1) was 0.13MJm–2 day–1 8C–1 higherthan in the crop cut at GS 32. Despite the greater delay inflowering in later cut crops (GS 45 and GS 61), the reductionin PTQ was less, due to cooler growing conditions during thepre-heading period (Table 4). Hence, there was no relationshipbetween PTQ and grain yield or grain number in the firstexperimental year.

In the second experimental year (2009–10), cutting before orat early stem elongation (i.e. GS 23–32) resulted in a very smalldelay in anthesis of <5 days and �100 degree days(Table 4). Meanwhile, a delay of 9–13 days occurred in cropmaturity when the crop was cut after GS 30. Again, thisphenological delay was less than the period between cuttingtimes, and the main delay was in the period to early booting(GS 41). This delay was maintained until the start of flowering,and again there was a reduced period from start of flowering tomaturity, and a shortened grain-filling period when the crop wascut after early booting (GS 41). Pre-heading PTQ decreased withlater cutting andgreater delays in cropphenology.Comparedwiththe uncut crop (1.45MJm–2 day–1 8C–1), the 2-day delay inflowering after cutting at GS 26 and GS 29 reduced pre-

heading PTQ by 0.09MJm–2 day–1 8C–1, and later cutting atGS 32 and GS 45 further reduced pre-heading PTQ (0.11 and0.13MJm–2 day–1 8C–1, respectively) (Table 4). Nitrogen

Table 3. Effect of cutting date and phenological growth stage (GS) on forage yield (t DMha–1) and quality ofwinter wheat cv. Longyu 216 at Qingyang, China, in the 2009–10 growing season

DAS, Days after sowing. Quality indicators: CP, crude protein (%); NDF, ADF: neutral/acid detergent fibre (g kg–1);ash (g kg–1). Topdressing rates were averaged for each cutting date because no significant nitrogen effect was observed.

Values in parentheses are standard errors

Date of cutting DAS GS Forage Forage quality indicatorsCP NDF ADF Ash

21 Oct. 2009 37 23 0.82 (0.09) 24.9 (1.7) 445 (12) 260 (14) 108 (3)9 Dec. 2009 86 25 1.31 (0.12) 20.2 (1.3) 519 (19) 306 (15) 89 (4)21 Mar. 2010 188 26 1.38 (0.15) 24.2 (0.8) 601 (10) 360 (37) 110 (3)5 Apr. 2010 200 29 1.58 (0.14) 23.4 (1.1) 554 (12) 381 (18) 117 (5)20 Apr. 2010 215 32 2.28 (0.16) 21.4 (1.1) 470 (5) 263 (5) 86 (5)5 May 2010 230 45 2.59 (0.27) 16.6 (1.3) 534 (8) 341 (25) 77 (2)

l.s.d. (P= 0.05) 0.26 1.5 39 57 6

Table 4. Delay in phenology (flowering and maturity, days), change inphoto-thermal quotient (PTQ, MJm–2 day–1 8C–1) calculated for theperiod 30 days before anthesis (GS 65), and increase in accumulatedthermal time (degree-days) at booting (GS 40), flowering (GS 60), andcrop maturity (GS 92) of wheat cut at different times compared with theuncut control for experiments in the 2008–09 and 2009–10 growing

seasonsNitrogen effectwas not significant anddata aremeans for all topdressing rates.

Values in parentheses are standard errors

GS at cut Delay inphenology

Changein PTQ

Increased accumulatedthermal time

Flowering Maturity GS 41 GS 61 GS 92

Experiment 1: 2008–09 season32 10 10 –0.13 161 (18) 129 (9) 217 (19)52 25 16 0.02 345 (28) 385 (11) 358 (13)61 33 20 –0.05 525 (21) 575 (18) 445 (30)

l.s.d. (P= 0.05) 36 24 34

Experiment 2: 2009–10 season23 0 3 0.01 48 (4) 0 (2) 39 (4)25 0 2 –0.03 58 (0) 13 (6) 26 (4)26 2 3 –0.09 50 (3) 38 (4) 37 (4)29 2 4 –0.09 55 (2) 38 (4) 61 (5)32 3 9 –0.11 58 (0) 50 (4) 131 (5)45 17 13 –0.13 372 (3) 359 (2) 212 (4)

l.s.d. (P= 0.05) 7 10 12

Table 2. Effect of cutting date and phenological growth stage (GS) on forage yield (t DMha–1) and quality ofwinter wheat cv. Xifeng 19 at Qingyang, China, in the 2008–09 growing season

DAS, Days after sowing. Quality indicators: CP, crude protein (%); NDF, ADF: neutral/acid detergent fibre (g kg–1);ash (g kg–1). Values in parentheses are standard errors

Date of cutting DAS GS Forage Forage quality indicatorsCP NDF ADF Ash

15 Apr. 2009 198 32 1.20 (0.08) 17.0 (0.4) 581 (8) 310 (18) 57.8 (3.3)3 May 2009 226 52 1.96 (0.20) 13.6 (0.2) 482 (3) 258 (20) 41.9 (1.6)17 May 2009 240 61 2.21 (0.21) 10.0 (0.4) 617 (6) 326 (9) 40.0 (0.5)

l.s.d. (P= 0.05) 0.32 4.3 15 32 3.4

Dual-purpose use of winter wheat in China Crop & Pasture Science 523

topdressing treatment did not significantly affect phenologicaldevelopment.

Crop yield and yield components

In both growing seasons, there was a large negative impact ongrain yield when crops were cut after the initiation of stemelongation, resulting in >62% reduction in grain yield and>54% reduction in maturity biomass (Tables 5 and 6). Evengreater reductions in grain yield and maturity biomass (>86%)occurred when the crop was cut after booting (GS 45 and GS 52)(Tables 5 and 6). The effect of cutting after stem elongation wasfar greater on grain yield than on maturity biomass, as evidencedby the lower harvest index with later cutting treatments. Thesecond year results show that cutting at GS 32 andGS 45 reducednumber of grains per m2 by 51% and 85%, respectively, whichwas mainly due to reduced spikes per m2 (50% and 68%reduction) (Table 6). Cutting at GS 32 did not change thenumber of grains per spike but kernel weight was reduced by22%. Later cutting at GS 45 further reduced kernel weight by52%, and reduced grains per spike by 55% compared with theuncut control.

In the second growing season, reduction in grain yield andplant biomass from cutting treatments before stem elongation(GS 23–26) was less (14–21%).Most of this reductionwas due todecreased spikes per m2 (7–18% reduction), which consequentlyreduced grains per m2 by 13–19%. All other yield components(kernel mass and grains per spike) were comparable with theuncut control (Table 6).

The effect ofNongrain yieldwas not significant, but therewasa clear and significant increase in maturity biomass under highertopdressing levels for the same cutting date (Fig. 1a). Underhigher N application rate, the reduction in crop biomass at

maturity for cutting times before GS 30 was less than underlower N application rate. The uncut control produced 13.4 t ha–1

of total crop biomass, while total biomass production, includingforage removed by cutting, when the crop was cut beforetillering (i.e. GS 23, 25, 26) was just 5% lower. This suggeststhat ensuring sufficient N is available during crop regrowthmay help alleviate yield reduction after cutting. No significantdifference in crop harvest index or yield components was foundbetween N topdressing rates (data not shown).

Grain quality and crop total N uptake

In both growing seasons, grain crude protein was dramaticallyincreased by cutting after booting (i.e. GS 52 and 61), indicatingthat the crop experienced water stress and/or reduced grainfilling duration, which resulted in smaller kernels and hencehigher protein concentrations (Table 5 and Fig. 1). Nitrogentopdressing increased grain crude protein in the uncut andearlier cut treatments but did not affect it when the crop wascut at GS 45, which was higher under all N treatments (Fig. 1b).

Crops cut after GS 30 recovered poorly, resulting insignificantly reduced final biomass and grain yield; thedemand for N in these crops was low and there was no valuein applying N post-cutting. In contrast, crops cut before stemelongation (GS 30) recovered well; these crops had high Ndemand and responded to additions of N after harvest(Fig. 1c). This additional crop N uptake was more-or-lessequivalent to the N removed in the forage biomass. The Ndemand and consequent recovery of N by the cut crops washigher than that of uncut controls supplied with additional N atthe same time. For example, when an additional 120 kgN ha–1

was applied, only 33% was recovered in the uncut treatment,while 50–70% of added N was recovered in crops cut before GS

Table 5. Effect of time of cutting on grain yield and maturity biomass (t ha–1), harvest index (HI), grain protein content(CP, %), and total crop N uptake (forage plus maturity biomass, t ha–1) in the 2008–09 growing season

Values in parentheses are standard errors

GS at cut Grain yield Biomass HI Grain CP Total N uptake

Uncut 1.95 (0.13) 5.23 (0.27) 0.37 (0.01) 15.0 (0.2) 77.1 (5.0)32 0.67 (0.03) 2.16 (0.06) 0.31 (0.01) 10.8 (0.2) 80.1 (2.8)52 0.26 (0.02) 1.12 (0.06) 0.23 (0.04) 21.0 (0.1) 70.5 (3.2)61 0.07 (0.01) 0.47 (0.04) 0.15 (0.01) 21.7 (0.1) 73.3 (2.4)

l.s.d. (P= 0.05) 0.28 0.48 0.05 0.6 10

Table 6. Time of cutting effects on grain yield and biomass (t ha–1), plant height (cm), and yield components of winter wheat in the 2009–10 growingseason

HI, Harvest index; kernel weight in mg. Data presented are means of three nitrogen topdressing rates treatments. Values in parentheses are standard errors

GS at cut Grainyield

Biomass Plantheight

HI No. of spikesper m2

No. ofgrains per spike

10�3� no. ofgrains per m2

Kernelweight

Uncut 5.8 (0.4) 13.6 (0.5) 107 (2) 0.43 (0.01) 579 (35) 25.6 (0.9) 146.7 (7.6) 39.7 (0.2)23 4.8 (0.5) 11.4 (0.7) 102 (2) 0.42 (0.01) 474 (26) 25.4 (0.8) 120.2 (8.2) 39.6 (0.6)25 5.0 (0.4) 12.1 (0.5) 96 (3) 0.41 (0.01) 540 (21) 23.5 (0.6) 126.6 (6.6) 39.2 (0.6)26 4.6 (0.4) 12.4 (0.5) 102 (1) 0.38 (0.01) 507 (29) 24.3 (1.8) 119.7 (6.1) 38.8 (0.4)29 4.2 (0.4) 10.8 (0.5) 98 (2) 0.39 (0.01) 511 (18) 21.9 (0.6) 111.9 (6.8) 37.6 (0.3)32 2.2 (0.2) 6.2 (0.3) 76 (1) 0.36 (0.01) 292 (16) 25.0 (1.7) 71.6 (4.8) 31.0 (0.7)45 0.4 (0.1) 1.9 (0.2) 66 (1) 0.22 (0.01) 186 (16) 11.6 (0.7) 21.9 (3.2) 18.9 (0.9)

l.s.d. (P= 0.05) 0.52 1.2 5 0.02 64 3.5 13.6 1.6

524 Crop & Pasture Science L. H. Tian et al.

30 (calculated from data in Fig. 1). When no additional N wasadded, N uptake in cut crops was similar to the uncut control.

Discussion

Forage production potential from dual-purpose wheat

Winter wheat cut for forage during its vegetative growth stageswould provide a useful, high-quality forage source for livestockin north-west China. Widespread winter wheat plantings acrossthis region are a potential resource to overcome the regular feedgap occurring in early spring and thus improve the productivityof livestock in regional, mixed farming systems. Forage yieldand quality measured during the vegetative stage in early springwas similar to reports in other environments where dual-purposewheat is currently used (0.8–2.7 t DMha–1 with 200–250 g crude

protein kg–1) (Pandey 2005; Merchan et al. 2007). In the small-holder,mixed farming systemsof theLoessPlateau, this untappedfeed resource would be sufficient to provide around 600 sheep.days of feed (at 2 kg per sheep per day) from each hectare ofwheat harvested. However, this amount of forage is likely to varysubstantially from year to year depending on seasonal rainfall,crop variety, early crop nutrition, and other factors. Furthermodelling to investigate the amount and reliability of thisavailable forage is required. One constraint in this region is therapid crop development in spring, which means there is a short‘safe’ window for biomass harvesting during the vegetativephase, and this may cause management problems for labour-constrained pen-feeding systems. Controlled grazing of fieldsmay be a more feasible, less labour-intensive option. Usingwheat forage before stem elongation reduces the risk of

0

2

4

6

8

10

12

14

16

021060

Bio

mas

s at

mat

urity

(t D

M h

a–1)

Uncut

GS23

GS25

GS26

GS29

GS32

GS45

10

12

14

16

18

20

22

021060

Gra

in C

P (

% D

M)

80

120

160

200

240

280

120600

Tot

al N

upt

ake

(kg

ha–1

)

(c)

(b)

(a)

021060

021060

N applied (kg ha–1)

Fig. 1. Effects of time of cutting and nitrogen topdressing on (a) total crop biomass produced by maturity, (b) graincrude protein (CP) content, and (c) total crop nitrogen uptake (i.e. includes forage removed, grain, and stover N) in the2009–10 season. Interactions between cutting time and nitrogen were not significant in other parameters.

Dual-purpose use of winter wheat in China Crop & Pasture Science 525

significant yield reductions, but unless this forage is stored untilspring, its value for livestock would be minimal because at thistime there is a plentiful supply of other forages.

Effects of cutting on grain yield and yield components

We found that cutting later than stem elongation (GS 30) reducedgrain yield significantly (>60%), due mainly to the removal ofgrowing points and subsequent death of these tillers. Reducedtiller survival as found in this research was also found to beresponsible for large yield reductions in other studies (Miller et al.1993). Smaller but important reductions in kernels per spike andkernel weight also occurred, indicating that the crop had reducedcapacity to allocate resources tograin production andgrainfilling.According to Virgona et al. (2006), grazing allows a greaterpenetration of light into the canopy, which initiates more tillersthat rarely result in fertile heads andmay increase competition forassimilate, particularly at key times before and after anthesis. Thecuttings post stem elongation in this study also resulted in ashortened grain-filling period (130–150 degree-days), whichreduced time for radiation interception and net assimilationand could also contribute to the reduction in kernel weight(Harrison et al. 2011b).

Our study found that even cutting before stem elongationreduced grain yield by 17–28%, which is a large reductioncompared with yield reductions observed by others. Forexample, Virgona et al. (2006) report average reductions ingrain yield of 4� 20% due to early grazing/cutting.Nonetheless, large yield decreases have been reported in otherstudies where defoliation has occurred before stem elongation(Pumphrey 1970; Dann et al. 1983). One explanation for thegreater reductions in our study may be the lower cutting height(0 cm) compared with other grazing or cutting studies. Greaterremoval of biomass is also generally more detrimental to yield,and increasingly so with later cutting (Harrison et al. 2011a).Arzadún et al. (2006) found that cutting at 3 cm reduced grainyield more than cutting at 7 cm, and grain yield reductions weredue to reduced number of spikes per m2. Our severe cutting atground level left very low residual biomass and is likely to haveremoved growing points, resulting in the reduced spike numberin the cut treatments, thus having a larger impact on crop recoveryand grain yield than the less severe cutting treatments in otherstudies.

In the second experimental year, wet spring conditions meantthat the uncut crop had little water stress; hence, any slowing ofwater use due to defoliation did not benefit the defoliated cropsduring grain filling, as was reported by Harrison et al. (2011b)andVirgona et al. (2006). On the other hand, we observed similargrain yield reductions for crops cut at the same stage (GS 32)in two growing seasons. Recent model simulation showed thepotential for inclusion of dual-purpose crops into traditionalgrain-only systems where the growing-season rainfall is>300mm (Harrison et al. 2011a).

Cutting effect on crop phenology

The results from this study support those of others where cuttingor grazing before stem elongation (GS 30) resulted in only smalldelays (0–5 days) in crop phenological development (Virgonaet al. 2006) and defoliation at later growth stages resulted in

greater delays in crop development (Royo et al. 1997).We foundthat this delay was in the period before booting and is probablya result of the removal of reproductive primordia and theadditional regrowth time required to reinitiate new floral stemsfrom the secondary tillers (Harrison et al. 2011a). The delay inphenology was less than the interval between times of cutting,suggesting these secondary or tertiary tillers that were notremoved by cutting had already been initiated. This is alsosupported by our results which show that cutting after stemelongation significantly reduces tiller numbers; hence, onceearly tillers were removed, the crop did not initiate sufficientnew tillers to compensate. When cuts were made after earlybooting (GS 41), there was a significant reduction in thermaltime between start of flowering andmaturity and reduced harvestindex via reductions in kernel size, indicating the shortenedduration of grain filling.

Pre-heading photo-thermal quotient was calculated to explorethe degree to which delays in crop phenology might be related toreductions in crop yield. Changes in pre-heading photo-thermalquotient due to changes in crop phenology were not sufficientto explain grain yield reductions, particularly in crops cut afterGS30. In both years, the yield reduction in crops cut later thanGS30 was far greater than would be explained by reduced pre-heading PTQ found elsewhere in wheat (Ortiz-Monasterio et al.1994). Kernel weight was decreased in crops cut after GS 29,which is likely to be due to the shorter duration of graindevelopment observed. In crops cut before GS 30, there wasa small decline in pre-heading PTQ due to small delays inflowering, and grain yield reductions were similar inmagnitude to those predicted from other studies relating pre-heading PTQ to grain yield in spring wheat without defoliation(Ortiz-Monasterio et al. 1994).

Clearly, there would be a strong seasonal interaction witheffects of cutting on crop development; delays may favour cropsin some years and not in others depending on the timing ofweather conditions. For example, a similar physiological delayin maturity and a similar grain yield reduction occurred in cropscut at the same stage (GS 32) in both experimental seasons, eventhough 10 day delay of flowering in cut crops for the first yearwas 7 days later than cut crops in the second year. In additionto direct impacts on grain yield, a problem of delaying cropdevelopment in this part of China is access to contract harvestersafter the majority of crops have been harvested. This wouldsignificantly affect farm management by delaying the plantingof following crops.

Crop nitrogen management

Nitrogen responses observed in this study showed that additionalN after cutting/grazing improved crop regrowth and grainprotein content. Nitrogen removed by cutting at tillering was33–50 kgN ha–1, and similar to the 38 kgN ha–1 removed undergrazing in previous studies elsewhere (Virgona et al. 2006). Ina cut-and-carry system such as our experiment, biomass N wasremoved from the system and not returned in excreta fromgrazing animals; hence, additional N supply may be requiredto replace this removed N. We found a response to 60–120 kgN applied, which suggests that 1.5–2 times more N than wasremoved in cut forage is required to ensure that crop regrowth is

526 Crop & Pasture Science L. H. Tian et al.

not N-deficient. Despite the biomass response to applied N, therewas no yield increase, and hence N efficiency was highest inthe non-fertilised treatment. This finding confirmed the highercrude protein content but lower N fertiliser recovery undergrazing conditions (Virgona et al. 2006). When wheat was cutafter stem elongation, the large reduction in crop N uptake andthe lack of response to additional N suggests that the cropsdemand for N is reduced by the decreases in tiller and grainnumber.

Conclusions

Winter wheat may contribute to alleviating the spring feedgap experienced by livestock producers in north-west China.Consistent with other studies, cutting before stem elongation(GS 30) is required to avoid large reductions in grain yield. Inthis environment, there is only a short period (50 days) whena crop could safely be cut for forage in spring. Further workis required before dual-purpose use of wheat could berecommended to mixed farmers of north-west China, inparticular, determining the optimum height and intensity ofcutting to maximise crop recovery, the most suitable cultivarsunder the environmental conditions of north-west China, thepotential to modify traditional sowing dates to produce moreforage, and the economics of grain-only cropping compared withthe dual-purpose use of wheat.

Acknowledgments

The research reported in this paperwas fundedby theNationalBasicResearchProgram of China (2007CB106804) and the Australian Centre forInternational Agricultural Research (LWR/2007/191). The Crawford Fundis acknowledged for sponsoring a traineeship for Tian Lihua with CSIRO inAustralia. The technical support in crop and soil data collection by the staffat the Qingyang Research Station of the Lanzhou University is greatlyacknowledged.

References

Arzadún MJ, Arroquy JI, Laborde HE, Brevedan RE (2006) Effect ofplanting date, clipping height, and cultivar on forage and grain yield ofwinter wheat in Argentinean Pampas.Agronomy Journal 98, 1274–1279.doi:10.2134/agronj2005.0313

Christiansen S, Svejcar T, Phillips WA (1989) Spring and fall cattlegrazing effects on components and total grain-yield of winter wheat.Agronomy Journal 81, 145–150. doi:10.2134/agronj1989.00021962008100020002x

Dann PR (1968) Effect of clipping on yield of wheat. Australian Journalof Experimental Agriculture and Animal Husbandry 8, 731–735.doi:10.1071/EA9680731

Dann PR, Axelsen A, Edwards CBH (1977) Grain yield of winter-grazedcrops. Australian Journal of Experimental Agriculture 17, 452–461.doi:10.1071/EA9770452

Dann PR, AxelsenA, Dear BS,Williams ER, Edwards CBH (1983)Herbage,grain and animal production from winter-grazed cereal crops. AustralianJournal of Experimental Agriculture 23, 154–161. doi:10.1071/EA9830154

Francia E, PecchioniN, NicosiaOLD, PaolettaG, Taibi L, FrancoV,OdoardiM, Stanca AM, Delogu G (2006) Dual-purpose barley and oat in aMediterranean environment. Field Crops Research 99, 158–166.doi:10.1016/j.fcr.2006.04.006

Harrison MT, Kelman WM, Moore AD, Evans JR (2010) Grazing winterwheat relieves plant water stress and transiently enhances photosynthesis.Functional Plant Biology 37, 726–736. doi:10.1071/FP10040

Harrison MT, Evans JR, Dove H, Moore AD (2011a) Dual-purpose cereals:can the relative influences of management and environment on croprecovery and grain yield be dissected? Crop & Pasture Science 62,930–946. doi:10.1071/CP11066

Harrison MT, Evans JR, Dove H, Moore AD (2011b) Recovery dynamicsof rainfed winter wheat after livestock grazing 2. Light interception,radiation-use efficiency and dry-matter partitioning. Crop & PastureScience 62, 960–971. doi:10.1071/CP11235

Holliday R (1956) Fodder production from winter-sown cereals and itseffect upon grain yield. Field Crop Abstracts 9, 129–135.

Hou FJ, Nan ZB, Xie YZ, Li XL, Lin HL, Ren JH (2008) Integrated crop-livestock production systems in China. The Rangeland Journal 30,221–231. doi:10.1071/RJ08018

Komarek AM, McDonald CK, Bell LW, Whish JPM, Robertson MJ,MacLeod ND, Bellotti WD (2012) Whole-farm effects of livestockintensification in smallholder systems in Gansu, China. AgriculturalSystems 109, 16–24. doi:10.1016/j.agsy.2012.02.001

Merchan HD, Lutz EE, Morant AE (2007) Production of a doublepurpose wheat defoliated at different developmental stages of thegrowth apex. Phyton-International Journal of Experimental Botany 76,133–142.

Miller GL, Joost RE, Harrison SA (1993) Forage and grain yields of wheatand triticale as affected by forage management practices. Crop Science33, 1070–1075. doi:10.2135/cropsci1993.0011183X003300050039x

MooreAD (2009)Opportunities and trade-offs in dual-purpose cereals acrossthe southern Australian mixed-farming zone: a modelling study. AnimalProduction Science 49, 759–768. doi:10.1071/AN09006

Ortiz-Monasterio JI, Dhillon SS, FischerRA (1994)Date of sowing effects ongrain yield and yield components of irrigated spring wheat cultivars andrelationships with radiation and temperature in Ludhiana, India. FieldCrops Research 37, 169–184. doi:10.1016/0378-4290(94)90096-5

Pandey AK (2005) Effect of agronomic practices on green fodder, grain yieldand economics of dual-purpose wheat (Triticum aestivum). IndianJournal of Agricultural Sciences 75, 27–29.

Peel MC, Finlayson BL, McMahon TA (2007) Updated world map of theKöppen-Geiger climate classification. Hydrology and Earth SystemSciences 11, 1633–1644. doi:10.5194/hess-11-1633-2007

Pinchak WE, Worrall WD, Caldwell SP, Hunt LJ, Worrall NJ, Conoly M(1996) Interrelationships of forage and steer growth dynamics on wheatpasture. Journal of Range Management 49, 126–130. doi:10.2307/4002681

Pumphrey FV (1970) Semidwarf winter wheat response to early springclipping and grazing. Agronomy Journal 62, 641–643. doi:10.2134/agronj1970.00021962006200050028x

Redmon LA, Horn GW, Krenzer EG, Bernardo DJ (1995) A review oflivestock grazing and wheat-grain yield-boom or bust. AgronomyJournal 87, 137–147. doi:10.2134/agronj1995.00021962008700020001x

Redmon LA, Krenzer EG, Bernardo DJ, Horn GW (1996) Effect of wheatmorphological stage at grazing termination on economic return. AgronomyJournal 88, 94–97. doi:10.2134/agronj1996.00021962008800010020x

Rodríguez A, Trapp JN, Walker OL, Bernardo DJ (1990) A wheat grazingsystems-model for theUnited-StatesSouthernPlains.1.Modeldescriptionand performance. Agricultural Systems 33, 41–59. doi:10.1016/0308-521X(90)90069-3

Royo C, Lopez A, Serra J, Tribo F (1997) Effect of sowing date and cuttingstage on yield and quality of irrigated barley and triticale used for forageand grain. Journal of Agronomy and Crop Science 179, 227–234.doi:10.1111/j.1439-037X.1997.tb00521.x

Sprague MA (1954) The effect of grzing management on forage and grainproduction from rye wheat and oats. Agronomy Journal 46, 29–33.doi:10.2134/agronj1954.00021962004600010009x

Dual-purpose use of winter wheat in China Crop & Pasture Science 527

Van Soest PJ, Robertson JB, Lewis BA (1991) Methods for dietary fiber,neutral detergentfiber, andnonstarchpolysaccharides in relation to animalnutrition. Journal of Dairy Science 74, 3583–3597. doi:10.3168/jds.S0022-0302(91)78551-2

Virgona JM, Gummer FAJ, Angus JF (2006) Effects of grazing onwheat growth, yield, development, water use, and nitrogen use.Australian Journal of Agricultural Research 57, 1307–1319.doi:10.1071/AR06085

Winter SR, Musick JT (1991) Grazed wheat-grain yield relationships.Agronomy Journal 83, 130–135. doi:10.2134/agronj1991.00021962008300010030x

Zadoks JC, Chang TT, Konzak CF (1974) Decimal code for growth stagesof cereals.Weed Research 14, 415–421. doi:10.1111/j.1365-3180.1974.tb01084.x

Zhu XA, Li YS, Peng XA, Zhang SG (1983) Soils of the Loess region inChina. Geoderma 29, 237–255. doi:10.1016/0016-7061(83)90090-3

528 Crop & Pasture Science L. H. Tian et al.

www.publish.csiro.au/journals/cp