Yield and phenological responses of bt cotton to different sowing dates in semi-arid climate

With the inclusion of BT cotton in the existing cotton-wheat cropping system of South Punjab, Pakistan; farmers are interested to sow early BT cotton to obtain its full production potential. There is a problem of sub and supra optimum temperature due to early and late sowing of BT cotton. Little efforts have been done to optimize the best sowing date of BT cotton in cotton-wheat cropping system. In this study, popular BT cotton cultivar MNH-886 was sown from February 14 till May 15, with two weeks interval, in soil filled earthen pots kept under natural conditions. Early sown (planted on February 14 and March 01) crop took more days to start emergence, complete 50% emergence and mean emergence time, and had minimum plant emergence. However, late sown (30^th April and 15^th May) took less time to germinate, with better and uniform seedling establishment. Although early planted crop took more days to start emergence, squaring, flowering, boll formation and boll opening but growing degree days to start emergence, squaring, flowering, boll formation and boll opening were high in late sown crop. However, BT cotton sown on 16^th March yielded better than all other sowing dates owing to increase in yield related traits like number of sympodial branches, bolls per plant and boll weight; while crop sown on 15^th May didn’t perform well. Likewise sowing of BT cotton on 16^th March had better fiber quality in terms of ginning out turn, fiber length, strength, fineness and uniformity. There was a positive correlation of phenological events like days to start squaring, flowering, boll formation and boll opening with seed cotton and lint yield of BT cotton; and cotton yield and boll weight were also positively linked with fiber quality traits. In conclusion, planting of BT cotton on 16^th March is the best option to harvest higher seed cotton and lint yield of better quality fiber under arid to semi–arid conditions of South Punjab, Pakistan.