Effect of time and rate of nitrogen application on cotton

Field studies were conducted in nine cotton production areas of Greece, for 15 successive years, to detective the optimum time and rate of N fertilizer application for maximum yields and better fibre characteristics of cotton (Gossypium hirsutum). Two to five rates of N fertilizer (60–180 kg N/ha) were applied: before sowing, when the plants had 3–4 leaves and 20 days later. The yield of cotton increased in most of the cases by N fertilization, but not significantly to both N rates and time of application. Under Greek conditions - limited growing season and low precipitation in spring - the split application of N fertilizers, compared to a single presowing application did not differ, as regards its effect on yield and fibre quality of cotton. Split application of fertilizers, supplementary to that applied at sowing could be of significance, when N plant demands are high and in addition there is a risk for excessive plant growth or for leaching losses. In the case of high N fertilizers rates, the split application must be preferred.