Management Practices to Control Premature Senescence in Bt Cotton

Field trial was conducted to investigate the effect of squares and fruiting branches removal under different levels of potassium fertilizer to measure premature senescence of Bt cotton at students’ Farm, University of Agriculture, Faisalabad, during 2011 and 2012. Experiment was laid out in a randomized complete block design (RCBD) with factorial arrangement using three replications. Experiment comprised of Factor A: (squares and fruiting branches removal) F₁: no fruiting branch removal, F₂: removal of first fruiting branch, F₃: removal of first and second fruiting branch, F₄: removal of all squares from first fruiting branch, F₅: removal of all squares from first and second fruiting branch; and Factor B: (potassium rates) K₁: 50 kg ha^-1, K₂: 100 kg ha^-1 and K₃: 150 kg ha^-1. Standard procedures were adopted for recording data for number of nodes above white flower, node above crack boll, plant height (at squaring, physiological cut-out and at maturity stage) and N percentage in leaves (at physiological cutout stage). More nodes above white flower were recorded in F₅, followed by F₃, while minimum were recorded in F₁. Among potassium levels maximum nodes above white flower were recorded in K₃ followed by K₂ and K₁ during both years of study. Plant height recorded at physiologically cut-out stage showed that plants gained more height with removal of all squares from 1^st and 2^nd fruiting branch with maximum level of potassium application and less plant height was recorded with no fruiting and/or square removal with minimum potassium application, similar trend was recorded when plant height was measured at full maturity stage during both years of study. Lower leaf N percentage was recorded K₁ as compared to K₂ and K₃. In conclusion early removal of squares/fruiting branches along with higher potassium dose will help in delaying canopy senescence in Bt cotton.