Two field experiments with cotton were conducted over two growing seasons on calcareous, heavy to medium textured, alluvial soils, to study the influence of N and P fertilizer rates, the method of fertilizer placement and the time of N fertilizer application on cotton yield, product quality and fertilizer utilization.
Nitrogen application up to 50 kg/ha in the first experiment and up to 120 kg/ha in the second experiment increased seed cotton yield; higher nitrogen rates in the first experiment had an adverse effect on seed production due to abnormal rainfall which caused an intense vegetative growth and delayed the time of maturity.
Split application of N at sowing and at early flowering was slightly superior to a single application at sowing or to split applications at sowing, early flowering and initiation of fruiting. Addition of nitrogen during the flowering stage failed to influence cotton production significantly.
Banding P and N fertilizers increased plant height significantly, compared with the broadcasting method; placement methods, however, did not significantly affect seed yield.
Increasing amounts of N and P fertilizers had essentially no effect on lint quality.
The phosphate concentrations in the tops derived from fertilizer phosphate, were low ranging from 1–2 to 2–4 % of the P concentration in the tops and it was not affected by the different treatments.
The utilization coefficients of the nitrogen fertilizer sources by cotton were high, nitrate N being utilized much more efficiently than ammonium N.