Effect of planting date on soybeans in the Namoi Valley, New South Wales

Abstract

The effect of planting date on phasic development, LAI, yield, yield determinants and seed quality of soybeans was studied in eight seasons. For all development phases up to the end of flowering, each phase was longer for longer daylengths within a cultivar, with later maturing cultivars having increasing sensitivity to daylength. LAI at flowering for each treatment was a function of time from flowering. The yield of Bragg and indeterminate cultivars (Wayne, Delmar and Ruse) decreased if planted in early November. There was generally a decreased yield at a late January planting due to small plant size (low LAI and few mainstem nodes) and in some instances, decreased seed size. Planting dates in December appeared to be optimum, although season and cultivar differences occurred. Seed oil content decreased and protein content increased as planting was delayed.