Impact of Sowing Dates on Terminal Heat Tolerance of Different Wheat (Triticum aestivum L.) Cultivars

Terminal heat stress leads to significant yield reduction in wheat. Adaptation strategies to combat this could be either growing heat-tolerant cultivars or adjustments in sowing date. A study was conducted for 2 years to understand the impact of terminal heat stress on wheat using three different wheat cultivars (HD 2932, WR 544 and HD 2967) and three sowing date, viz. D1 (second week of November), D2 (first week of December) and D3 (last week of December) at Indian Agricultural Research Institute (IARI), New Delhi, India. Results revealed that timely sown crop (D1) showed significantly higher number of tillers m−2 (450), plant height (93.5 cm), 1000-grain weight (38 g), grain yield (6.3 t ha−1) and harvest index (0.44) compared with D2 and D3. Yield loss occurred by 70, 29 and 77 kg ha−1 per day due to delay in sowing beyond D1 in varieties, viz. ‘HD 2932,’ ‘WR 544’ and ‘HD 2967,’ respectively. The late-sown crop resulted lower yield, which encountered higher temperature in its terminal growth stages. Among three varieties used, ‘WR 544’ had lesser decline in growth and yield than other two varieties due to late sowing. It implied that ‘WR 544’ had thermo-tolerant characteristics. Higher yield in wheat requires both heat-tolerant cultivars and better agronomic strategy under terminal heat stress condition. This study concluded that varietal selection and adjustment in sowing date could be the appropriate adaptation strategies under changing climate especially the terminal heat stress.