Drought stress is a major agricultural challenge that affects the growth and yield of crops, especially soybean. This study aimed to evaluate the effects of nano-fertilizer foliar application on soybean agronomic traits under drought stress conditions. The experiment was designed as a factorial arrangement in a Completely Randomized Design (CRD) with three replications in the greenhouse of the University of Kurdistan in 2019. The experimental treatments included five nano-fertilizer foliar application levels (0, 1.5, 3, 6, and 12 cc per liter) and three irrigation levels (100%, 80%, and 60% field capacity: full irrigation, moderate stress, and severe stress, respectively). Foliar application was carried out at two stages: flowering and pod-filling. The traits assessed were plant height, height of the first pod from the ground, number of pods per plant, number of seeds per plant, number of seeds per pod, electrical conductivity (EC), and seed yield in the pot. The results indicated that nano-fertilizer foliar application reduced the negative effects of drought stress and improved several agronomic traits of soybean. The highest seed yield in the pot was recorded in the treatment with 12 cc per liter nano-fertilizer and 100% irrigation, while the lowest seed yield occurred in the control treatment (no nano-fertilizer) under severe drought stress (60% field capacity). Additionally, electrical conductivity (EC), as an indicator of osmotic stress, was highest in the severe drought treatment without nano-fertilizer, whereas the lowest EC was observed in the 80% field capacity and 3 cc per liter nano-fertilizer treatment. These findings suggest that nano-fertilizer application can mitigate drought stress, improve nutrient uptake, reduce osmotic stress, and enhance soybean growth and yield. Overall, nano-fertilizer use, especially under drought conditions, can improve water use efficiency and contribute to sustainable soybean production. These results provide a scientific basis for optimizing water and nano-fertilizer usage in sustainable agriculture under drought stress conditions.
