Sweet corn responses to basal and top-dressed rates and sources of nitrogenous fertilizers

Abstract

Sweet corn (Zea mays L. var. rugosa cv. Jubilee) was grown on a fine loamy clay krasnozem soil with banded nitrogen fertilizer at rates up to 200 kg N ha-1 from (NH4)2SO4 and 50 kg N ha-1 from each of NH4NO3 and urea. Some treatments were top-dressed with one or two applications of 50 kg N ha-1. The highest yield of both cobs (23.1 t ha-1) and fresh shoots (93.8 t ha-1) and the highest concentration of N in cobs and shoot dry matter was attained with 100 kg basal N ha-1 and two subsequent topdressings of 50 kg N ha-1 each, applied as (NH4)2SO4. From banded dressing alone, 150 kg N ha-1 produced the highest cob yield and the highest accumulation of N in cobs and shoot dry matter. Top-dressed N increased the yield of cobs and the yield and N concentration in shoots, but did not influence the N concentration in cobs. As N rates were increased, there was an increase in the weight of primary cobs, the weight and number of secondary cobs and more significantly, in the number of tertiary cobs. The source of N did not have any effect on the yield or most yield related components except yield and number of tertiary cobs, which were higher in the ammonium sulfate treatments. The contribution of nitrogen uptake efficiency NUPE and nitrogen ultilization efficiency NUTE to variations in nitrogen use efficiency NUSE was calculated and discussed.