Influence of soil type and irrigation on yield of spring‐sown barley and peas and autumn‐sown greenfeed in Canterbury

Abstract Close linear correlations were obtained between yield of spring‐sown crops and evapotranspiration calculated for each of four soil types and irrigation treatments in Canterbury. Available soil water storage, derived from soil depth (which was the only soil factor used to represent soil types), was shown to be the major soil factor determining crop yield. Under dryland conditions, barley and pea yields were greatly affected by each soil's available water storage capacity. In the two driest seasons, crops grown on the deep soils yielded 2–3 times higher than those on the shallow soils. Under irrigation, soil type differences were less important and, where adequate water was supplied, crops grown on shallow soils produced yields equivalent to those from deep soils. Relative crop responses to irrigation of the different soils were dependent upon the nature of the season and the timing of irrigation. In drier seasons, whenever irrigation treatments failed to eliminate severe water deficit stress in crops on the shallow soils, crops grown on the deeper soils had larger responses to the same irrigation treatment. In moister seasons, or where irrigation treatments maintained adequate water for crops growing on shallow soils, the shallow soils showed greatest crop responses to the water applied. In certain seasons irrigation suppressed yields on some deeper soils. Greenfeed grown on shallow soils commonly had lower yields than on deeper soils and this was partially attributed to nitrogen deficiency. Differences in yields were reflected in differences in grain and pea weights and in other yield components in peas. Nitrogen contents of barley grain showed only small variations between soils but large variations between seasons. Soil types had significant effects on barley screenings percentages, particularly under dryland conditions. Quality differences between soil types were lessened or eliminated through irrigation.