EFFECTS OF FOLIAR APPLICATION OF POTASSIUM ORTHOPHOSPHATE ON GRAIN YIELD AND KERNEL QUALITY OF WHEAT (Triticum aestivum) UNDER TERMINAL HEAT STRESS

A field experiment was conducted at Bangladesh Agricultural Research Institute (BARI) farm, Gazipur to evaluate the effect of foliar application of potassium orthophosphate on grain yield and kernel quality of wheat under the terminal heat stress imposed by late sowing for two consecutive years (2008-09 and 2009-10). Five combinations of foliar applications of potassium orthophosphate and Tilt were tested on three wheat varieties, namely Kanchan, Shatabdi, and Prodip. The result indicated that foliar application of potassium orthophosphate was effective in increasing SPAD value (Measure of leaf chlorophyll content) and leaf area of all the wheat varieties, whereas Tilt application was effective only in Kanchan. The grain size of wheat in terms of 1000-grain weight was improved and thereby contributed to grain yield. Also the foliar application of potassium orthophosphate decreased the number of immature, smaller and deformed kernel, and thus improved the kernel quality. Two foliar sprays of 0.1% potassium orthophosphate solution at 70 DAS (Days after sowing) and 80 DAS performed better results than other applications. There were varietal differences in response to foliar treatments and the variety Prodip and Shatabdi were more responsive to potassium orthophosphate compared to Kanchan. Potassium orthophosphate could be suggested to improve grain yield and kernel quality of wheat under terminal heat stress condition. Keyword: Osmotic solute, heat stress, wheat genotype, kernel quality, SPAD value Introduction Intensive farming of cereal crops in order to produce more food often compels the late sowing of wheat under the rice based cropping systems in Bangladesh. Late-sown wheat is usually exposed to high temperature during flowering to grain-filling stages of the crop due to short spell of winter in Bangladesh (Ahmed and Meisner, 1994). High temperature enhances leaf senescence and reduces green area duration that affects the production of photosynthates and thereby results in shrivels and smaller grains (Rahman et al., 2005). The yield reduction of wheat under higher temperature is associated with a less number of 1 Regional Wheat Research Centre, Bangladesh Agricultural Research Institute (BARI), Gazipur 1701, 2 Crop Physiology Division, BARI, Gazipur 1701, 3 Wheat Research Centre, BARI, Nashipur, Dinajpur, Bangladesh.