EFFECT OF FRUITING BRANCH REMOVAL AND NITROGEN RATE ON COTTON SENESCENCE

Removal of early fruiting branches with optimum nitrogen dose caused more source and less sink at early stages leading to delay in onset and progression of senescence in cotton. Field trials were conducted to investigate the effects of squares and fruiting branches removal under different nitrogen levels on the growth of Bt cotton at Students' Farm, University of Agriculture Faisalabad, during 2011 and 2012. Experiment was laid out in randomized complete block design (RCBD) with factorial arrangement using three replications. Treatments comprised of manual alteration of plant architecture (F-1: no fruiting branch removal, F-2: removal of first fruiting branch, F-3: removal of first and second fruiting branch, F-4: removal of all squares from first fruiting branch, F-5: removal of all squares from first and second fruiting branch) and nitrogen rates (N-1: 175, N-2: 225 and N-3: 275 kg ha(-1)). Results exhibited more number of nodes above white flower (NAWF) recorded in F-5, followed by F-3, F-4 and F-2 while minimum NAWF recorded in F-1. Among nitrogen levels maximum nodes above white flower were recorded in N-3 followed by N-2 and N-1 during both years of study. Before manual alteration of the plants architecture, no variation in plant height was observed at squaring stage, but at physiologically cut-out stage plants gained more height with removal of squares/fruiting branches with maximum level of nitrogen. Shorter boll maturation period was recorded in F-4 and F-5 than in F-1, F-2 and F-3. Lower earliness index was observed in F-5 and F-3 and higher earliness index in F-1. Longer boll maturation period, earliness index and seed index were recorded with 275 kg N ha(-1). Removal of first and second fruiting branch and removal of all squares from first and second fruiting branch along with higher nitrogen dose helped in delayed onset of senescence in cotton leading to improved translocation of assimilates towards economic part and thus more seed cotton yield (data not given).