Abstract
Response of six different upland cotton genotypes to various nitrogen levels (0, 50, 100 and 150 kg N ha(-1)) was studied during crop season 2010 at Khyber Pakhtunkhwa Agricultural University, Peshawar, Pakistan. Highly significant differences in yield and yield parameters were observed among cultivars, nitrogen levels and the interaction of cultivars vs. nitrogen levels for the given parameters. Application of N significantly increased plant height, sympodia per plant, bolls per plant, boll weight and seed cotton yield but various cultivars responded differently in term of percent increase over control. Maximum value of the given parameter for the given cultivar was observed at higher N level of 150 kg N ha(-1). However, when percent increases in the given parameter was considered, it was observed that those cultivars having lower growth and yield traits at control responded more to N application than those having initially higher growth traits which could be due to genetic variation and efficient use of N. Overall, the cultivar CIM-506 maintained higher plant height, sympodia per plant, boll per plant, boll weight and seed cotton yield at all nitrogen levels suggesting that it could be the promising cultivar under environmental conditions of Peshawar and could be grown by supplying 150 kg ha(-1) N. Since a linear increase in all growth parameters was observed up to 150 kg N ha(-1) for all cultivars, studies with further higher doses (levels beyond 150 kg ha(-1)) are recommended for the confirmation of the findings of present study.