Effect of potassium fertilization on water productivity, irrigation water use efficiency, and grain quality under direct seeded rice-wheat cropping system

A two-year field investigation was conducted to find out the right time, method, rate and source of potassium (K) fertilization for maximizing nutrient and water use efficiency and quality in a basmati rice-wheat cropping system. The split application of a recommended dose of K (RDK = 60 kg K2O ha(-1)) as half basal (B) and remaining half at panicle/ear initiation (PI/EI) stages significantly increased the system water productivity (SWP) (0.60 kg ha(-1)mm(-1)) and system irrigation water use efficiency (SIWUE) (1.26 kg ha(-1)mm(-1)) by 9.1% and 7.1% respectively over basal application of entire RDK. Likewise, in basmati rice, the split application of 100% RDK increased the water productivity (WP) and irrigation water use efficiency (IWUE) by 10.9% and 10.6% respectively over basal dressing of 100% RDK. The split application of RDK and supplementation of K through foliar spray besides basal K application increased the nitrogen, phosphorus and potassium concentration in grain and straw of both the crops. With respect to grain quality, the split application of 100% RDK increased the protein content by 2.3% in basmati rice, and 2.8% in wheat over basal application of 100% RDK. Similarly, the split application of RDK increased the hulling, milling and head rice recovery percentage of basmati rice by 1.3%, 6.6% and 3.3% respectively over basal application of RDK. The root length and dry weight of wheat was increased by 6.9% and 21% by split application of RDK over basal dressing of same dose of K.