Optimizing water-stressed mungbean for climate-smart sustainable intensification: Potassium's role in improving soil moisture, physio-biochemical traits, and yield sustainability

Agronomic management offers a practical approach for cultivating mungbean (Vigna radiata L. Wilczek) under water-stressed dry conditions. This study investigated the effects of water stress (WS) on mungbean yield productivity, plant water relations, and physicochemical changes in response to different potassium (K) application rates. Two genotypes—drought-resistant BMX-08010-2 (G1) and sensitive cultivar BARI Mung-1 (G2)—were employed alongside seven levels of potassium fertilization treatments, namely, well-watered + recommended K fertilization (RKF) in the form of muriate of potash (KL₁), WS + RKF (KL₂), WS + 25% additional K with RKF (KL₃), WS + 50% additional K with RKF (KL₄), WS + 75% additional K with RKF (KL₅), WS + 100% additional K with RKF (KL₆), and WS + 125% additional K with RKF (KL₇). All treatments were conducted under a rain-out shelter using a split-plot design with three replications. The results revealed that various physicochemical and agronomic traits were affected under WS, including water use efficiency (WUE), chlorophyll content, relative water content, xylem exudation rate, membrane stability index, proline, and soluble conditions, particularly temperature depression, biological yield, harvest index, and seed yield productivity. However, the application of additional K (KL₃–KL₇) improved the performance of all these traits under WS conditions, with the most notable improvement observed at the highest application level (KL₇). Specifically, the KL₇ treatment increased WUE to 8.14 kg ha⁻¹ mm⁻¹ and grain yield to 1093 kg ha⁻¹, whereas the KL₂ treatment, without additional K, recorded the lowest WUE (4.73 kg ha⁻¹ mm⁻¹) and grain yield of 825 kg ha⁻¹. Compared to lower K applications under WS, the KL₇ treatment resulted in a 32.52% increase in grain production, with overall yields ranging from 1410 kg ha⁻¹ using 281 mm water (KL₁) to 825 kg ha⁻¹ using 175 mm water (KL₂). These findings support the role of K supplementation in mitigating the adverse effects of WS and offer a promising strategy for using this approach as a model for enhancing WUE and crop resilience in achieving sustainable water development under climate-smart agricultural practices.