The effect of planting date on the yield and some fibre properties of cotton in the Namoi Valley

Abstract

The effect of planting dates between September 30 and November 30 on the yield and some fibre properties of two cotton cultivars has been studied over three seasons. The yield of the commercial cultivar (Deltapine Smoothleaf) fell by an average of 20 kg ha-1 day-1 delay in planting after October 20, earlier planting dates having equal yields, producing a plateau effect. The yield of an early maturing cultivar (Short Sympodial) fell linearly by 11 kg ha-1 day-1 delay in planting. Planting dates after mid-October had an adverse effect on micronaire in the commercial cultivar, but lint length and strength were not affected. Thus maximum yield and micronaire for plantings after mid-October came from the early cultivar. Tolerance to low temperature is an important factor in cultivar earliness, and accounts for the performance of Short Sympodial in these experiments. The number of days from first flower to first frost was as reliable as growing degree days in explaining yield variation within a cultivar