Nanochelated Iron Outperforms Ionic Iron in Kidney Bean (Phaseolus vulgaris L.) Productivity Under Drought Stress

Drought stress poses a formidable abiotic challenge that severely curtails crop productivity. This study evaluated the effectiveness of foliar-applied nanochelated iron (nanochelated-Fe) compared to ionic Fe²⁺ in kidney bean ( Phaseolus vulgaris L.) under both nondrought and drought conditions. A one-year field trial was performed following a randomized complete block design consisting of three replicates (six plants per treatment), and P. vulgaris grown under nondrought (70% field capacity) and drought (50% field capacity) stress was foliarly treated with equivalent concentrations of nanochelated-Fe or ionic Fe²⁺ (0, 50, 200, 500, and 1000 mg Fe L − 1 ) and compared with untreated control. Untreated plants under drought stress had significantly lower photosynthetic pigments, underscoring the vulnerability of the crop to drought. Remarkably, foliar application of 1000 mg L − 1 nanochelated-Fe under drought resulted in significant increase in grain yield (47%), protein content (21%), protein yield (78%), and grain iron (36%) compared to untreated control. Under non-drought conditions, similar benefits were recorded with 27%, 22%, 55%, and 31% increases in grain yield, protein content, protein yield, and grain Fe concentration, respectively. Moreover, nanochelated-Fe treatment outperformed ionic Fe²⁺ by providing an extra 7% increase in protein content and an 8% enhancement in grain Fe concentration. These superior outcomes are attributed to the nanochelated-Fe’s ability to mitigate oxidative stress, modulate proline and carotenoid levels, reduce electrolyte leakage, and improve relative water content. These findings demonstrate that nanochelated-Fe may serve as a sustainably effective strategy for improving kidney bean production and nutritional quality, particularly in regions experiencing moderate drought stress.