Heat stress remediation of rice (Oryza sativa L.) growth and development, and nutrients uptake through fertilizers management in tropics

Increased evidences have shown that agricultural crop production to be constrained by heat stress that can significantly reduce crop growth and development as well as nutrients uptake. Nitrogen and potassium are two macro-essential nutrients that influence a number of biochemical and physiological processes that involve in crop production, and also contribute to the survival of crop exposed to high temperature tension. Therefore, the current glasshouse experiment was conducted to explore the effect of nitrogen and potassium fertilizers application on the resistance of rice against heat stress. The highest decrease in morphological and physiological characteristics were observed in aborted spikelets per panicle about 2 time, chlorophyll content by 4.23% and plant height by 2.43% over control, meanwhile the fertile spikelets per panicle by 38.5%, grain yield by 25.25%, the numbers of tillers per hill by 10.76% and effective tillers per hill by 9.1% decreased in heat stress pots. In case of macronutrients uptake, the highest decreased in N uptake was observed in straw by 12.45% and followed by total (12.21%) and grain (11.68%), meanwhile K uptake was decrease in order of grain(28.96%)> total (18.26%)>straw (13.43%) (P<0.05). The highest rate of single N application in both sources remediated the morphological characters between 15 to 63%, meanwhile the single K application increased them about 2%. Also, the fertilizers management remediated the negative effect of heat stress in order of: yield (<2 times), fertile spikelets (< 2 times), effective tillers (57.6%) and 1000 grains weight (about 4%) compare to control in applied heat treatments. With respect to single application of N and K that increased the N and K uptake (grain, total and straw) averagely about 2.2 and 1.2 times more than control at heat stress pots, respectively, the highest levels of urea and applied K, increased all uptake parameters averagely about 2-3 times.