CROP PLACEMENT AND ROW SPACING fact sheet - Grains ...

higher yields than 40cm spacing,which was too wide to reach the yieldpotential (Figure 1). This yield lossequates to 0.5t/ha for every 10cmincrease in row spacing.In central Queensland, trials comparedthe effect of 25, 37.5 and 50cm rowson wheat yields. For yields up to 2t/hathere was no effect on increasing rowspacing up to 50cm. When averageyields were between 2t/ha and 4t/ha,there was a 0.2t/ha yield reductionwhen rows were widened from 25 to37.5cm. The yield reduction was0.3t/ha when the row spacing wentfrom 25 to 50cm. The greatest penaltiesoccurred in crops where the averageyield exceeded 4t/ha, with a reductionin yield of 0.6t/ha when rows wereextended from 25 to 37.5cm, while theaverage yield loss was 0.5t/ha whenrow spacing went from 25 to 50cm.Broadleaf cropsPulse yields are more tolerant of widerow spacing than cereals.ChickpeasPlanted on a row crop configuration(up and back on 50 to 100cm rows)chickpeas can benefit from a reducedincidence of ascochyta blight byimproving airflow between the rows.The wider row spacing can reducespray costs by allowing for bandedspraying. Harvesting height isimproved if the chickpeas are sownon the inter-row, between the rows ofthe previous cereal crop. This enablesthe standing stubble to act as a trellis.Newer chickpea varieties with geneticresistance to ascochyta blight mayresult in a re-evaluation of row spacingfor this crop in the future.Field peasRow width for field peas should be25cm or less if sown into bare fallowsbut can be increased to 15 to 35cmplanted into standing stubble.MungbeansAs a break crop, mungbeans are oftensown at 50cm to 1m row spacingas this suits the configuration ofmachinery used for the primary crops.However, mungbeans can be sown atnarrower row spacing. Narrow rows(less than 50cm) have a higher yieldpotential, where yields are likely tobe greater than 1t/ha. Data suggeststhe yield increases from narrow rowspacing can be as much as 10 to 15per cent, for potential yield of 2t/ha.CanolaIn NSW, trials have evaluated canolasown on 18, 24 and 36cm rows butresults have been inconclusive. Poorseasons have resulted in variableinformation on how plant densityhas translated into yield and moreresearch is currently underway.A series of canola trials in WesternAustralia has shown an average yieldloss of 13.7 per cent by widening rowspacing from 18 to 36cm. Recent trialswith Brassica juncea at Coonambleand Edgeroi, NSW, showed significantyield losses of approximately 20 percent on a 1.8t crop when row spacingmoved from 30 to 45cm for latesowing. The yield loss was less withearlier sowing.SunflowerSeveral row spacing configurationshave been tried in sunflower, includingskip row (every third row missed),wide rows (1.5m spacing) and thestandard 75cm spacing. Preliminarytrials conducted by Pioneer Hi-Bred Australia and AgriScienceQueensland, DEEDI in centralQueensland indicated that 1.5m rowspacing can offer better utilisation ofmoisture when available moisture isscarce, helping to maintain yield.Other benefits include more evenflowering and maturity, faster maturityby up to 10 days, cleaner harvest andlower planting seed costs. However,weed control can become moredifficult under wider row spacing.SorghumThe traditional spacing for sorghum is60cm to 1m depending on machineryconfigurations and expected yield(Table 1). Narrow rows typically outyieldwide rows under good growingconditions and are more appropriatein high rainfall environments or withirrigated crops.The lack of soil moisture in dry yearshas resulted in wider and skip rowconfigurations being used to improveyield reliability. In some areas therehas been a move to grow sorghumon ultra wide 1.5m rows. Single skip(two rows 1m apart with a 2m spacingfollowed by two rows 1m apart) anddouble skip (two rows with a 3mspacing before another two rows)have become popular as a way ofconserving soil moisture.Wide and skip row configurationspromote yield stability, particularly inlow yielding years by limiting crop wateruse during the crop vegetative phaseand, therefore, maximising the wateravailable during flowering and grainfill. There is a cost in reduced potentialcrop yield in a good year. The increasedpost-flowering water availability in askip row configuration reduces the riskof crop failure in a dry year.The choice of row spacing can bemade at the time of sowing afterassessing the water content of thesoil profile and seasonal outlook.The extra wide row and skip rowconfigurations enable a shieldedsprayer to be used for weed control.FIGURE 1 Significant reductionsin cereal yield when row spacingincreased from 30 to 40cmGrain yield (t/ha)5.04.84.64.44.24.03.83.63.43.23.060 120 200Target plant population (plants/m 2 )30cm 40cmSOURCE: Guy McMullen, I&I NSWSoil moistureTable 1 Suggested row configurations for potential sorghum yields inQueensland and New South WalesPotential yieldOptimum row spacingAbove 4t/ha1m or less3 to 4 t/ha 1mBelow 3t/ha1m or more and skip row configurations become an optionSource: Guy McMullen, I&I NSW

Seeding depthFIGURE 2 The effect of sowing depth and the timeof sowingGrain yield (t/ha)2.52.0(57)1.51.0(126)0.50EarlyDeepSowing time and depthMainShallowThe difference in emergence and development between wheatsown at 30 to 35mm and sown too deep or shallow.Crop establishment is a critical component in maximising cropyield. Seeding depth is an important factor in achieving even plantpopulations and more recently has influenced growers’ ability tosow on time.Factors which influence a seedling’s ability to emerge from depthinclude seed size, seed treatments and herbicides, coleoptile length(varies with variety), soil conditions and temperature.Unnecessarily sowing too deep can delay emergence, reduceestablishment of early seedling vigour, increase diseasesusceptibility and reduce yields. In some seasons moistureseeking or deep sowing is a tool that can ensure crops areestablished in their optimal sowing window.Deeper sowing may reduce plant populations, but the yield from theearlier sowing may offset any potential yield losses and increaseyields compared with delaying sowing to later in the season. In2007, trials at Yallaroi in northern NSW compared the deep sowingof a range of barley varieties against delayed sowing at a shallowerdepth. This trial clearly showed the impact of deeper showing onplant establishment with half the plants established compared to theshallow planting (Figure 2).The main effect was that earlier sowing and crop establishment,using deep seed placement, provided a 1t/ha yield advantage. Grain(Early = May 23, Main = June 19) on barley yield and establishmentin 2007 (plants/m 2 in brackets)quality was also greatly improved with lower screenings comparedto the later sowing.Although the ideal seeding depth for wheat and barley is 30 to 70mmthis will vary based on variety. Research in barley has shown thatmost commercial varieties respond similarly to deep sowing. Twoexceptions to this in recent research have been Hindmarsh A andFitzroy A that have not emerged as well from depth. Caution should betaken with these varieties when deep sowing.Some fungicidal seed treatments can also reduce coleoptile lengthand seedling vigour in cereals and treated seeds should be shown atas shallow a depth as possible.The ideal seeding depth for sorghum is between 20 to 50mm.Canola has small seeds and should be sown shallow with the idealdepth 12 to 25mm.Pulses such as chickpeas and field beans, which have hypogealemergence where the cotyledons remain where the seed is sownand only the shoot emerges from the soil, tolerate sowing at depthsof 50 to 80mm.A more uniform seeding depth is achieved with press wheels whichminimise the variation in soil cover, provided they leave a regular,stable furrow.

photo: GUY MCMULLENWide and skip row configurations (ultra wide at 1.5m shown) promote yield stability, particularly in low yielding years, by limiting crop water useduring the crop vegetative phase. There is a cost in reduced potential crop yield in a good year.Closer row spacing can reduceevaporation by increasing the rate ofcanopy closure. Wider row spacingcan increase evaporation from thesoil between the rows but this can beoffset by inter-row stubble retention.Skip row configurations in sorghumresult in crop residues being left inbands after harvest, leaving interrowspaces bare of cover. Reducedstubble cover can cause increasedrun-off and soil loss and reducedinfiltration and fallow water storage.This can make inter-row areas difficultto ‘wet-up’ and can restrict futureplanting options.The effect of reduced soil wateraccumulation in the following cropneeds to be weighed up against theenhanced yield of the current crop in adry season.Any extra water accumulated duringa fallow period can dictate whetheror not a crop can be sown in thefollowing year.Weed competitionIncreasing row spacing can createweed problems. Wider spacingreduces the crop’s ability to closethe canopy and compete with weedsbetween rows. This delays inter-rowweed suppression – the wider therows the longer the delay.As row spacing increases to morethan 40cm in cereals, canopy closuremay never occur making weed controlextremely important.Wider row spacing allows for weedsto be controlled using higher ratesof incorporated by sowing (IBS)herbicides, such as trifluralin andpendimethalin, with tined seederswhere a ‘hot blanket’ of herbicide isincorporated in-between the croprows.Wide row spacing in some cropsenables weeds to be controlledthrough inter-row cultivation andcreates the potential to use a shieldedsprayer to control weeds betweencrop rows.EquipmentWide row spacing can cut machinerycosts by reducing the numberof sowing units on a machine.Consequently, less fuel and possiblya smaller tractor could be used forsowing.Increased sowing speeds are alsopossible. Wider row spacing reducessoil throw and the impact of preemergentherbicide being thrown fromone row into an adjacent row, where itcan reduce crop emergence. Soil throwdistance increases with the square ofspeed. That is, doubling the speed willincrease soil throw distance by four.So, speed can increase approximately1.4 times if row spacing is doubled.Wider row spacing can improve thestubble handling ability of seedingequipment. There can be problemswhen stubble loads are heavy.Discs are ideal for stubble retentionbut are not as versatile as tinedmachines, which can be easilyreconfigured for different crop and soil

Inter-row sowing can improve stubble flow and help establishment. The best results are achieved with row spacings of 30cm or more and using +/-2cm accuracyguidance and autosteer. Row spacing for cereals and pulses is often determined by sorghum.photo: emma leonardconditions. Triple disc seeders are lessefficient at herbicide incorporation andpre-planting weed control than tinedor culti-trash machines.Culti-trash machines are good athandling heavy stubbles but make itdifficult to control seed depth and canresult in inconsistent establishment.Tined machines are less able tocope with stubble than disc seedersand often require preparation of thestubble at harvest.Inter-row croppingIn combination with GPS guidancethat provides at least +/-10cmaccuracy and autosteer, wide rowspacing allows subsequent crops tobe located on the inter-row. Inter-rowsystems can improve stubble flow butit is important that tines do not catchthe stubble row as this can causeestablishment problems.When RTK guidance provides+/-2cm accuracy, the best results areachieved when the minimum wide rowspacing is approximately 30cm.Wider row systems can potentiallyhelp with the move to disc seedersand full zero-till systems.Inter-row sowing spacing with cerealand pulse crops is often determinedby the spacing used for sorghum.FertiliserFertiliser rates may need to be refinedfor wide row spacing. Wider rowspacing can result in an increasedconcentration of fertiliser in rows or areduced fertiliser rate per hectare atseeding. Consequently, changes in theamount of fertiliser applied at seedingand additional fertilisation during thegrowing season may be required withwider row spacing.Increased fertiliser requirementscan occur when there is incompleteexploration of the surface soil by plantroots, such as in dry years.Banding fertiliser below the seed willhelp minimise the effects of fertilisertoxicity. This can occur if seedingfertiliser rates are maintained but rowspacing increased.Soil fertility can also vary betweenthe row and inter-row space in widerow cropping systems. There may beresidual applied phosphorus in thecrop following a dry year. Nitrogenfixation following pulses or nutrient