ABSTRACT

Responses of three cotton cultivars (Gossypium hirsutum L.) to soil-applied nitrogen (N) fertilization rates were evaluated for three years on an Hebert silt loam soil (fine-silty, mixed, thermic Aeric Ochraqualfs). Few significant (á=0.05) cultivar by N-rate interaction differences were found, although main effects of the N-treatments and the cultivars were evident. The most pronounced responses of the cotton were found as an effect of the N-fertilization treatments. N-rates in excess of 100 lb N/acre were not found to significantly increase lint yields in any year of the study. The mean yield of the cultivars among N-rates was significantly different only one year. Earliness of the cotton was reduced by increasing N-rate as indicated by significant differences in nodes above white flower (NAWF) measurements. Significant differences were also found in the NAWF measurements for the cultivars, thereby inferring maturity differences among the cultivars tested. 'Arkot 518' was found to be the earliest, 'Stoneville 4531 was moderate, and 'Deltapine 901 was the latest maturing cultivar. Significant interactions of cultivar and N-rate were found only in the final plant heights of one year (1991), in three dates of NAWF (1991), and one date of petiole nitrate-nitrogen (NO₃ -N) content (1990).