Crop Production in the East of Scotland - SASA

Crop Production in the East of ScotlandYields and Yield PotentialCerealsThe yield of a particular crop depends upongenotype, management, season and landcapability class, and their interactions. Forexample, in a survey of nearly 500 farmcrops of spring barley in the East ofScotland over five seasons, 1978-82 (Hay,Galashan & Russell, 1986), there was a verywide range of farm yield from 1.2 to 7.8 tha -1 (at 15% m.c.). However, national andinternational statistics have tended toindicate that cereal yields on farms inScotland tend, on average, to be higher notonly than those in other northern countries(e.g. Table 1.1) but also than in England andWales.This phenomenon was first investigatedexperimentally in 1976 and 1977 bycomparing the growth and physiology oftwo spring barley varieties under the samemanagement at Cambridge (52º11’N) andPathhead near Edinburgh (55º53’N) (Kirby& Ellis, 1980; Ellis & Kirby, 1980). Over thetwo contrasting seasons (severe drought in1976), the grain yields of the Pathheadcrops were 79% higher than at Cambridge;the differences could be explained in termsof up to 64% higher ear populationdensities, up to 17% more grains per ear,and up to 20% higher individual grainweights. It was concluded that the longerphotoperiods (more than 15 hours frommid-April to late August) and lowertemperatures at Pathhead (i.e. similarsupplies of solar radiation distributed overlonger days; Chapter 2) permitted longerdurations of each developmental phase, andlonger growing seasons overall. Inconsequence, more organs (tillers, ears,spikelets, florets) were initiated and/orfewer organs aborted; and there wasgreater interception of solar radiation tosupport these organs.This provided the first unequivocal supportfor the hypothesis that the yield potentialof adapted crops, such as spring barley, canbe higher under cool long days, although itshould be noted that not all comparisonsgive such clear results (e.g. Ellis & Brown,1986). Since then, there has been a seriesof experiments at different latitudes inScotland, England and France, designed toinvestigate the environmental control ofdevelopment and yield in wheat (e.g. Kirbyet al., 1987; Porter et al., 1987; Delécolle etal., 1989; Hay & Delécolle, 1989). Theconcept of slow and prolongeddevelopment, with extended grain filling,delayed senescence and enhancedinterception of radiation, explains whyMidlothan holds the world record for theyield of a field crop of wheat (as opposed tosmall plot yields) at 14 t ha -1 (Hay, 1993).A study was conducted in the early 1980s(Hay et al., 1986; Hay & Galashan, 1988) toTable 4.3The yields of cereal crops (t ha -1 at 15% m.c.) in the South Eastof Scotland, 1978-82.Spring BarleyWinter WheatAll farms 4.7 (474) n/aSpecialist arable farms 5.0± 0.06 (265) 5.9 (149)Variety trials 5.6 ± 0.21 (110) 6.4 (48)Calculated maximum potential 9.2 13.234Values are means over five seasons ± s.e. with number of farms in brackets (adapted from Hay etal., 1986).