Response of new cotton varieties to nitrogen fertilization in Sudan Gezira

The growth and yield responses of three newly released cotton varieties to nitrogen fertilization were evaluated in a two-year (2006-2007) field experiment at Gezira Research Station (GRS), Central Sudan. Three cotton varieties, (Hamid, Khairalla and Knight) and six equidistant N rates (0, 30, 60, 90, 120 and 150 kg N/ha) were arranged in a split plot design. The varieties were the main plot and N rates were the subplot with 4 replications. Results indicated similar trends of response of the three varieties, but with varying relative responses of each variety to nitrogen rates. Significant differences in yield potential among the three varieties were detected. Averaged across the nitrogen rates, variety Hamid gave 31 and 14% yield advantages over varieties Khairalla and Knight, respectively. Cotton growth, seed cotton and lint yields were significantly and progressively increased with the rise in the levels of added nitrogen. The yield response of each variety to N increments was best expressed by a quadratic response model.