Impact of straw return and nitrogen fertilizer on photosynthesis and yield of red kidney beans.

Red kidney bean (Phaseolus vulgaris L.) is widely cultivated and consumed globally. Exploring the effects of straw return and nitrogen fertilizer on the growth and yield of red kidney beans is essential for developing optimal straw return and nitrogen management practices to increase grain yield for food security. Field experiments were conducted for three consecutive years (2022-2024) to study the effects of two straw return methods and four nitrogen fertilization levels on the chlorophyll content, photosynthetic characteristics, dry matter accumulation, yield and its components of red kidney beans. The results showed that chlorophyll content, photosynthetic characteristics, dry matter accumulation, yield and its components improved significantly under straw return (ST) compared to no straw return (NST). Increasing nitrogen supply can promote the effect of straw return. Across all three seasons, the ST + N135 treatment produced the highest values for all measured traits. Chlorophyll content, Pn, Gs, Tr, dry matter accumulation, and yield increased increased 28.91-34.60%, 22.40-28.65%, 27.83-30.67%, 25.68-27.89%, 23.45-28.62%, and 17.08-21.05% under ST + N135 treatment. The ST + N90 treatment yielded the highest planting profit at $6378.84 per hectare. Our findings demonstrated the ST + N90 treatment was an effective way to achieve stable, high yields of red kidney beans and maximize farmers' income, which could be promoted and applied in Inner Mongolia.