Effect of split application of potassium on nutrient recovery efficiency, soil nutrient balance, and system productivity under rice-wheat cropping system (RWCS)

Improving nutrient use efficiency and system productivity with a positive nutrient balance in rice-wheat cropping system (RWCS) is vital for long-term food security. Two-year field trials were conducted with the objective of computing the effect of different rates, time, method, and source of potassium (K) fertilization on nutrient recovery efficiency, nutrient balance, and system productivity in a dry direct-seeded RWCS with eight treatments. The two-split (half basal and half at panicle initiation) application of 60 kg K2O/ha resulted in 37.5% and 19.2% increase in recovery efficiency of K in rice and wheat, respectively over basal application of 60 kg K2O/ha. Besides, the split-application of K increased the nitrogen recovery efficiency in rice and wheat by 11.2% and 10.8%, respectively. Similarly, the phosphorus recovery efficiency was increased by 3.6% and 7.4% in rice and wheat, respectively. The split application of 60 kg K2O/ha also increased the K harvest index (% of the total K absorbed is transferred to grain) by 0.7% and 2.7% in rice and wheat, respectively over applying entire K at basal. Similarly, the system productivity (11.26 t/ha) was increased by 8% over applying entire K at basal. In the absence of top-dressing of K (30 kg/ha), two foliar-sprays of 2.5% K provide equal benefits of top dressing. Application of 90 kg K2O/ha lowered the K negative balance (-99 kg/ha/year) considerably compared to two-split application of 60 kg K2O/ha (-152.5 kg/ha/year). Thus, optimization of K fertilization in RWCS will increase the system productivity, nutrient use efficiency, and sustainability.