Growing Degree Day Requirements and Yield Ability of Irrigated Durum Wheat as Influenced by Sowing Time

The growing degree day requirements and yield performance of durum wheat sown at two dates (1 and 30 November) were evaluated in a field experiment conducted during rabi seasons of 2010–11, 2011–12 and 2012–13 at Ludhiana. The increased growing degree days, heliothermal units and photo-thermal units requirements depicted that the accumulated heat units were significantly higher in timely sown (1 November) crop. The higher phenothermal index of timely sown wheat suggested longer growing period of each phenophase resulting in more accumulation of thermal units both at flowering and maturity stages, which resulted in higher yield attributes and grain yield. Timely sown wheat recorded significantly higher crop biomass and grain yield than late sown (30 November). The pooled data analysis confirmed that timely sown crop had prolonged tillering phase and grain filling periods than late sown crop. The cultivar PDW 314 had greater accumulation of thermal units and significantly higher biomass than cultivars PDW 291 and DBW 17. The three cultivars recorded similar wheat grain yield.