Abstract

Rice (Oryza sativa) production is pivotal to the economy and food security in India; the country is second only to China in annual production. Nevertheless, and in spite of a significant increase during recent decades, yields lag behind potential rice productivity. Accurate and sophisticated mineral nutrition is a promising approach to enhance rice yield. The objectives of the present study are to examine and demonstrate the effects of potassium (K) dose, the number and timing of MOP (muriate of potash, KCl) application during the crop cycle, and the contribution of foliar SOP (sulphate of potash, K₂SO₄) at the reproductive stage on crop performance and productivity. The experiment took place at Chidambaram, Tamil Nadu, between June and September (Kuruvai), and included nine treatments: unfertilized control; standard nitrogen (N) and phosphorus (P) at 100 and 50 kg ha^-1 of N and P₂O₅, respectively; standard NP + 25 kg K₂O ha^-1 (soil-applied MOP, split into two applications) + two sprays of SOP at 1%, or 2%; standard NP + 37.5 kg K₂O ha^-1 (soil-applied MOP, split into two applications) + two sprays of SOP at 1%, or 2%; standard NP + 50 kg K₂O ha^-1 (soil-applied MOP, split into four applications); and, standard NP + 50 kg K₂O ha^-1 (soil-applied MOP, split into three applications) + a single SOP spray at 1%, or 2%. Grain yields gradually increased from 2.37 Mg ha^-1 under unfertilized control to 3.7 Mg ha^-1 under the 50% K rate, and further to 5.5 Mg ha^-1 under the highest K dose + SOP. Foliar SOP applications during early reproductive stages (panicle initiation and heading) had a significant effect on yield, with stepwise yield increments of 5-14%, on average. Based on these results, it is postulated that further optimization of NPK supply, including split N and K doses and foliar applications, adjusted as required during crop development, would lead to increased rice productivity.

Keywords: Foliar spray; harvest index; MOP; Oryza sativa; SOP; split application.