Urea application and time of harvest effects on seed production of Setaria anceps cv. Narok

Abstract

Three levels of urea (50, 100 and 200 kg N ha-1 crop-1) and three methods of application were tested on four irrigated crops of Setaria anceps cv Narok grown for seed on a grey-brown podzolic soil. Pure seed yield was increased by urea application at post-harvest cleaning cut. The second year summer crop was more responsive to nitrogen than the seedling or the autumn crops. Inflorescence density exerted the primary control over seed yield. Urea application increased the tiller fertility and tillering of some crops. Negative compensatory effects were evident in seed density per unit inflorescence length. Late application of nitrogen at early heading increased the survival of late formed tillers which did not contribute to harvested seed yield. Optimum harvest time coincided with maximum seed density, usually occurred before maximum inflorescence density, and was associated with the inflorescences exserting 20 to 35 days previously.