Low nitrogen-use efficiency (NUE) is a serious issue for cotton production and environmental sustainability in arid climates. A pot study was conducted to evaluate the effect of K nutrition on NUE and performance of low- and high-K-efficiency cotton cultivars under two moisture regimes. Treatments included two soil moisture levels—i.e., normal irrigation, 100% available water content (AWC); reduced irrigation, 50% AWC—three levels of nitrogen (N)—i.e., 0, 375, and 750 mg N pot⁻¹—and two K levels, i.e., 0 and 208 mg K pot⁻¹. Results reveal that 208 mg K pot⁻¹ application with nitrogen significantly enhanced the N-use efficiency, growth, and yield attributes of both cotton cultivars compared with sole N fertilization. Similarly, the combined application of NK @ 375 N + 208 K mg pot⁻¹ caused up to 83% increase in NUE under AWC_50% and AWC_100%, as compared with NK control (0 N + 0 K). Compared with the control, imposed low-moisture stress caused a decrease of 13.9% in stomatal conductance (g_s), 2.5% in transpiration rate (E), and 6.5% in net photosynthetic rate (P_N), respectively_. The physiological water use efficiency (P_N/E) decreased by 13.2% under AWC_50%. Applied NK @ 375 N:208 K, mg pot⁻¹ caused 27.39 and 27.56% improvement in the P_N/E in HKE and LKE cultivars under AWC_50%, respectively. The HKE cultivar, i.e., CIM-554, maintained the highest g_s and P_N than FH-901, that was low-K-efficiency cultivar. The study suggests that varietal selection and adequate K fertilization have the prospects to improve NUE and save considerable quantities of fertilizer and irrigation water in cotton production under arid environments.

Climatic variations have created many challenges for farmers, but the most important one is the change in the dynamics of nutrient uptake by plants. Nutrients that were sufficient in soil are now found deficient, an issue that needs more focus in order to sustain crop productivity. Magnesium is very important plant nutrient that has a direct role in chlorophyll synthesis and interacts with other nutrients to manage physiological mechanisms. We designed field experiments focusing on the foliar application of magnesium at different growth and reproductive stages of a rice crop. Results reveal that the combination of rice cultivation system and magnesium application, i.e., flooded rice with Mg application at seedling + tillering + panicle initiation (F₆T₂), significantly improved crop growth and exhibited noticeable results in crop yield and grain quality. Moreover, the rice crop also recorded the highest benefit cost ratio (BCR) when kept flooded and fertilized with Mg at three stages; viz seedling, tillering, and panicle initiation; during both the years. Combined application of magnesium at growth and reproductive stages improved crop performance both in aerobic as well as in flooded rice, but the crop grown under flooded condition showed accelerated performance in both cropping seasons, which reflects its viability and economic feasibility.