YIELDING ABILITY OF WHEAT (TRITICUM-AESTIVUM) AT DIFFERENT DATES OF SOWING - A TEMPERATURE-DEPENDENT PERFORMANCE

A study conducted during the winter (rabi) seasons of 1987-88 and 1988-89 showed that late sowings decreased the grain yield of wheat (Triticum aestivum L. emend. Fiori & Paol.). The rate of reduction in grain yield was 12.34 +/- 7.28 kg/ha/day for delay in sowing beyond 15 November and 2 December respectively during 1987-88 and 1988-89. Regression equations were developed using 2 linear models for delay in sowing (D) and mean maximum temperature during period of ear growth (T). The predicted pattern of changes in grain weight/spike (GW), 1,000-grain weight (TGW) and grain yield (Y) fitted well with the observed pattern, showing linear reduction with delay in sowing. The maximum reduction in grain yield using either of the equations was found in 'UP 1182' and the minimum in 'UP 1179'.