Optimizing potassium fertilization rates for enhancing salt tolerance in maize and gram crops in rainfed, semi-arid region of India

Salt accumulation in the rhizosphere from ions like sulfate, chloride, and sodium hampers nutrient uptake, particularly in saline-alkali soils, limiting crop growth. Potassium (K) acts as an osmoprotectant, enhancing plant tolerance to these stresses. This study evaluated the effect of soil test-based potassium (ST-K) fertilization at varying rates (0%, 75%, 100%, 125%, and 150% ST-K) on the K/Na ratio in saline and alkali soils. Lab results showed that saline soils responded quickly to K fertilization, displacing Na, while alkali soils needed more time due to Na retention. Incubation study reveals that saline soils exhibited swift reaction to K fertilization, with K availability increasing immediately and Na being displaced. In contrast, alkali soils required longer periods to attain optimal potassium levels due to their higher tendency to retain sodium. Based on these findings, pot experiments were conducted with maize and green gram and results confirmed that 150% ST-K improved maize growth, including germination, height, yield, and nutrient uptake (N, P, Ca, Mg), while reducing Na and enhancing the K/Na ratio. Green gram showed a moderate response but still benefited from higher K levels. Field validation study highlights the importance of K fertilization in improving crop resilience and productivity in saline-alkali soils of arid region.