Effect of time of sowing on grain yield, and nutrient uptake of wheats with contrasting phenology

Four wheat genotypes with varying vernalisation and daylength requirements were sown in the field on 5 occasions between early April and late June at Wagga Wagga and Temora, New South Wales, in 1974 and 1975. The period between sowing and heading decreased from 1068-1 324 degree-days (base temperature = 4¦C) for crops sown in April to 660-841 degree-days for crops sown in late May. The genotype with the largest vernalisation response in this study (WW33G) produced the highest yields when crops were sown in early April. The cultivar Oxley, which has a small vernalisation response, produced the highest yields at almost all other sowing times. Shoot nitrogen (N) and phosphorus (P) uptake did not vary consistently in relation to the time of sowing. Grain protein concentration was higher at 3 of 4 sites with early sowing and grain P concentration was always significantly higher with early sowing dates. Higher concentrations of P were associated with higher concentrations of phytate. The concentrations of N and P were negatively correlated with yield and harvest index.