Combined foliar application of nano‐zinc and nano‐boron improves wheat yield and chlorophyll content under drought stress

Abstract Drought stress is a major limiting factor for wheat cultivation in semi‐arid regions, a problem often exacerbated by concurrent soil micronutrient deficiencies. While nanofertilizers can improve nutrient uptake and crop resilience, their specific interactions under defined drought stages are not well documented. This 2‐year field study assessed the impact of foliar‐applied nano‐zinc oxide (ZnO) and nano‐boric acid (H 3 BO 3 ) on the physiological traits and yield of wheat ( Triticum aestivum L. cv. ‘Bahooth 22’) under different irrigation regimes. The experiment used a split‐plot factorial design, with drought stress applied during the stem elongation stage in the main plots and nano‐fertilizer treatments (control, nano‐zinc, nano‐boron, and their combination) in the subplots. Drought stress markedly decreased plant height, fertile tiller numbers, and overall grain yield. However, applying nanofertilizers alleviated these negative impacts. Under water‐limited conditions, the combined application of nano‐zinc and nano‐boron increased grain yield by roughly 42% compared to the untreated control (from 1563 to over 2200 kg ha − 1 ). This yield boost was primarily driven by improved spike characteristics, specifically longer spikes and more grains per spike, rather than changes in 1000‐grain weight. Additionally, nano‐zinc was crucial for maintaining total chlorophyll content, which helped preserve photosynthetic capacity during the water deficit. These results indicate that strategically applying nano‐zinc and nano‐boron as foliar sprays can stabilize physiological functions and sustain yields, providing a practical nutrient management approach for wheat production in water‐scarce environments.