Integrated iron foliar application and phosphorus fertilization enhance yield and nutrient dynamics of mung bean in calcareous soils

Mung bean production in calcareous soils is often constrained by low nutrient availability, particularly iron (Fe) and phosphorus (P), which limit plant growth and yield. This study aimed to evaluate the effects of Fe foliar application and P fertilization on growth, yield, and nutrient dynamics of mung bean under calcareous soil conditions. A two-year field experiment (2022–2023) was conducted using a randomized complete block design with Fe foliar application (0, 0.2, 0.4, and 0.6%) and P fertilization rates (0, 30, 60 and 90 kg ha − 1 ). Iron and phosphorus applications significantly influenced yield components, physiological traits and nutrient accumulation. Foliar application of 0.4% Fe resulted in the highest thousand seed weight (39.42 g), biological yield (3132 kg ha − 1 ), seed yield (790 kg ha − 1 ) and crop growth rate (13.58 g m − 2 day − 1 ), representing increases of 12.21%, 12.54%, 23.44% and 44.47%, respectively over the control treatment. Similarly, phosphorus application at 60 kg ha − 1 significantly enhanced thousand seed weight (39.83 g), biological yield (3156 kg ha − 1 ) and seed yield (796 kg ha − 1 ), chlorophyll content (3.12 mg g − 1 ) and crop growth rate (13.48 g m − 2 day − 1 ) with increase of 14.49%, 14.06%, 32.89% and 26.22%, respectively compared with the unfertilized control. Seed and straw N (3.58% and 1.27%) and Fe concentrations (36.2 mg kg − 1 and 315 mg kg − 1 ) were highest under 0.6% Fe, while in case of phosphorus, the plots with 90 kg P ha − 1 produced the maximum seed and straw N (3.97% and 1.06%). The highest seed and straw P concentration (0.31% and 0.16%) was observed at 0% Fe, while application of 90 kg P ha − 1 also enhanced seed and straw P content (0.38% and 0.20%). Agronomic phosphorus efficiency peaked at 30 kg P ha − 1 (4.26 kg kg − 1 ) and 0.4% Fe (4.29 kg kg − 1 ), while total N uptake (41.51 kg ha − 1 ), seed carbohydrate content (62.79%) and soil P (7.02 mg kg − 1 ) were highest with application of 90 kg P ha − 1 . The foliar spray of 0.6% Fe resulted in higher total N uptake (40.45 kg ha − 1 ), seed carbohydrate content (61.19%) and soil P (6.79 mg kg − 1 ). Economic analysis revealed that the combined application of 0.4% Fe and 60 kg P ha − 1 produced the highest value cost ratio. The combined application of 0.4% Fe and 60 kg P ha − 1 is recommended for farmers to enhance mung bean yield and profitability under calcareous soil conditions, where Fe and P availability is often limited, whereas 0.6% Fe with 90 kg P ha − 1 is more effective for enhancing nutrient accumulation. This nutrient management strategy can be effectively adopted under field conditions to improve productivity and nutrient use efficiency.