Response of Bt. cotton to different nitrogen doses and plant spacing.

Cotton, a major cash crop of Pakistan, is considered backbone of the national economy and efforts are required to raise the per hectare yield. A field experiment was conducted at Central Cotton Research Institute Sakrand to assess the response of new cotton cultivar Bt. CRIS-508 during Kharif season, 2012 and 2013. A randomized complete block design (RCBD) in split plot arrangement was used with four nitrogen doses [N1 = 75kg N ha -1 , N2 = 100kg N ha -1 , N3 = 150 kg N ha -1 and N4 = 200 kg N ha-1] in main plots and three plant spacing [S1 = 15 cm, S2 = 23 cm and S3 = 30 cm] in subplots during 2012 and 2013. Nitrogen doses and plant spacing had significant effect on yield and yield components. Results revealed that during both the study years, N200 kg ha-1 significantly increased plant height, number of bolls per plant, boll weight, seed cotton yield (2.9 and 2.8 Mg ha-1) and nitrogen uptake compared than N50, N100 and N150 kgha -1 respectively. However, nitrogen uptake efficiency and nitrogen use efficiency was significantly lower in N200 kg ha-1 as compared with other nitrogen doses during both growing seasons. Cotton yield and yield components was increased by 30 cm plant to plant spacing while nitrogen uptake, nitrogen uptake efficiency and nitrogen use efficiency remained non- significant during 2012 and 2013. Plant height, number of bolls per plant, boll weight, nitrogen uptake, nitrogen uptake and use efficiency of nitrogen doses and plant pacing interaction remained non- significant while seed cotton yield showed significant response during both years.