Effect of different sowing dates on phenological development and heat unit requirements of wheat cultivars

A field experiment was conducted to determine the effect of sowing dates and cultivars on the growth and yield of wheat. The treatments comprised of six sowing dates (28^th October, 4^th November, 11^th November, 18^th November, 25^th November and 2^nd December) with four wheat cultivars (WH 1105, PBW 550, HD 2967 and PBW 621) in split plot design with three replications. The early sown wheat crop took more days to complete its life cycle as compared to late sown crop. Differences in growing degree days were observed between the wheat cultivars. PBW 550 consumed less number of growing degree days and pheno-thermal index as compared to HD 2967, WH 1105 and PBW 621 cultivars due to its short duration and attained physiological maturity earlier, and hence consumed less number of growing degree days. Amongst dates of sowing, value of pheno-thermal index was found to be higher at initial growth stages in earlier sown crop and at later growth stages in late sown crop. The heat use efficiency went on increasing from vegetative growth to grain filling and physiological maturity of the crop and it was higher in early sown as compared to late sown wheat crop.