Thermal Unit Requirement and Grain Yield of Wheat under Non-Irrigated Dry Warmer Condition

An experiment was conducted with four wheat genotypes (BARI Gom 28, BARI Gom 29, BAW 1177 and ESWYT 29) and two growing conditions (well water and non-irrigated water stress) during November, 2015 to March, 2016 at research field of Department of Crop Physiology and Ecology, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh. The experiment was carried out to investigate the effect of non-irrigated dry warmer condition on growing degree days (GDD), phenothermal index (PTI), heat use efficiency (HUE) and grain yield and also to assess the relation of grain yield with HUE of wheat genotypes. The results revealed that there was an increasing trend of GDD requirement from early to later stages and finally, the highest GDD requirement was observed at harvest maturity stage for all genotypes under both growing conditions. For attaining different phenological stages the maximum GDD requirement was observed in ESWYT 29 under well water conditions, whereas minimum GDD requirement for that was observed in BARI Gom 29 under water stress condition. Non-irrigated water stress reduced PTI in maximum cases of different phenophases but there was minimum variation in PTI between the two growing conditions. Non-irrigated water stress also reduced the grain yield and HUE in all wheat genotypes. The highest grain yield (4.20 t ha-1) and HUE (3.89 kg ha-1 ℃ day-1) based on grain yield was observed in BAW 1177 under well water condition, while the lowest grain yield (2.06 t ha-1) and HUE (1.92 kg ha-1 ℃ day-1) was observed in ESWYT 29 under water stress condition. The results of the present investigation also revealed that there was a strongly positive linear relationship between HUE and grain yield of wheat genotypes.