Grain yield and quality - HGCA

24 The wheat growth guideGrain yield and qualityMarketable yield depends on number of ears, grains in each ear and weight of each grain.Key facts– Grain dry weight usually constitutes about half offinal crop dry weight.– Grain yield can be estimated by multiplyingtogether ears/m 2 , grains per ear and weight ofeach grain (derived from thousand grain weight)which are determined at successively later stagesin the life cycle.– Grain yield is measured as the weight of grainrecovered from an area of crop, corrected to amoisture content of 15%.– Specific weight partly depends upon grain size,also on grain density and grain packingcharacteristics.– Hagberg falling number reflects the gellingproperties of flour made from whole grain.Grain yield11.0t/ha at 15% moistureGrain is the principal product of crop growth, especially inJune and July. Yields therefore depend on the state of thecrop leading into this period and then on growingconditions during this period.In experiments, yields may be determined by combineharvester or by hand-harvesting crop from a quadrat ofspecified land area. The benchmark crop yielded 11.0t/haby both methods, when corrected to 15% moisture.Yields vary with variety (see HGCA Recommended List)and growing conditions, as affected by soil, weather andhusbandry.Farm average wheat yields from UK Cereal Production SurveyUK cereal area (%)2010Currently, almost all average farmyields are below the benchmark.Yield components460 ears/m 248 grains/ear50mg/grainat 15% moistureEar number/m 2 , grains per ear, and grain weight are keyyield-determining attributes at harvest. Their values arerelated to the success of different growth phases:– ear number reflects growth from the start of tillering toflag leaf appearance (GS39)– grain number per ear reflects growth from GS39 toflowering (GS61), and– individual weight per grain reflects growth afterflowering.Each phase partiallycompensates for the outcome100 of earlier phases. A crop with asparse shoot density tends toproduce more grains per earand heavier grains than a thickcrop.50Cumulative % of area000 1 2 3 4 5 6 7 8 9 10 11 12Average farm yield (t/ha)source: Defra

25 The wheat growth guide Grain yield and qualityFinal distribution of dry matter18.4t/ha dry matter with51% Harvest IndexHarvest Index is the ratio between grain yield on a drybasis and the total crop dry weight at harvest. This ratio isvariable.Final dry matter distributionChaff2.1t/haLeaves and deadshoots 2.1t/haStructural stem5.7t/haGrain9.4t/haSoluble stemreserves 0.2t/haThe benchmark dry matter of the harvest-ripe crop is18.4t/ha, of which 9.4t/ha is grain (equivalent to 11.0t/haat 15% moisture).The remaining 9.0t/ha of dry matter includes straw, chaffand stubble, but only about half of this can be baled asstraw, even when the height of the combine cut is low.Much variability in crop dry weight comes through variableproduction of non-harvestable material. Plant breedershave been most successful in increasing harvest index;growers have been most successful in increasing totalcrop dry matter.Specific weight78kg/hlCrops with a large grain weight tend to have high specificweight. This is also influenced by:– the density of individual grains– the range of grain sizes– characteristics of grain surfaces that affect packing.Specific weight indicates the weight of grain that can beloaded onto lorries or ships. A typical requirement formilling or export is 76kg/hl; samples below this standardare likely to incur price penalties or even exclusion fromthe intended market. Late harvesting can reduce specificweight through weathering.Hagberg falling number270Hagberg falling number is a measure of the hot pasteviscosity of a wholemeal water suspension. The minimumvalue possible is 60.Values required:– above 250 for breadmaking– above 225 for export.Lower viscosity results from starch breakdown by theenzyme alpha-amylase. This may form during or afterripening.Enzyme activity is mainly associated with initiation ofgermination, and hence with sprouting. Alpha-amylasemay also form in cool, wet weather during ripening, evenin the absence of visible sprouting. Green grains on latetillers, or grains damaged by orange blossom midge alsohave high alpha-amylase.Effects of husbandry on Hagberg falling number tend to besmall and inconsistent compared to the effects of varietyand weather.Varietal differences in specific weight, dormancy andHagberg falling number are indicated in the HGCARecommended List. Group 1 wheats generally are classedas ‘very high’.What does it mean?By GS91 management can only protect against losses ofyield or quality. Depending on intended market and likelyrisks, consider:– combining as soon as the crop is ripe– assessing Hagberg falling number pre-harvest onhand-threshed, air-dried grain– harvesting at high moisture to optimise chances ofhigh Hagbergs.