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.

Kidney bean is an important edible legume crop characterized by a short growth period, strong stress resistance, and wide adaptability. Straw return combined with rational nitrogen fertilizer application is a crucial agronomic measure for improving kidney bean yield and economic performance. However, quantitative analyses of their combined effects on the photosynthesis, biomass, yield, and economic benefits of kidney bean remain insufficient. This study investigated the effects of two straw return methods and four nitrogen fertilizer rates (0, 45, 90, and 135 kg ha⁻¹) on chlorophyll content, photosynthetic characteristics, agronomic traits, root length, biomass accumulation, yield, and planting profit in a kidney bean cropping system in Inner Mongolia over two growing seasons. The results showed that straw return combined with nitrogen fertilizer significantly improved growth and photosynthetic indicators, as well as increasing yield and profit. At the same nitrogen application rate, straw return showed superior performance compared with no straw return. The promoting effect increased with nitrogen rate within the tested range (0-135 kg ha⁻¹). Among all treatments, straw return with 135 kg N ha⁻¹ achieved the relatively highest yield of 3130.73 kg ha⁻¹, while straw return with 90 kg N ha⁻¹ produced the greatest economic benefit of 6312.05 yuan ha⁻¹, which was 16.77% higher than the control. Considering overall performance, straw return with 90 kg N ha⁻¹ is favorable for balancing yield and economic returns, whereas straw return with 135 kg N ha⁻¹ is appropriate for pursuing higher yield. These findings provide theoretical and practical references for rational straw return and nitrogen management in kidney bean production.

To clarify the effects of biochar application on leaf photosynthesis, dry matter accumulation, and productivity in a maize–soybean intercropping system, a two-year field experiment was conducted in the Yellow River irrigation area of Inner Mongolia from 2024 to 2025. A split-plot design was adopted with two biochar application rates (0 and 5 t ha⁻¹) and three cropping patterns, including maize monoculture, soybean monoculture, and maize–soybean 2:4 intercropping. Leaf SPAD values, photosynthetic characteristics (Pn, Tr, Gs, and Ci), yield components, and land equivalent ratio (LER) were determined. Compared with maize monoculture, intercropping significantly increased maize SPAD values at the V12 and VT stages by 12.80% and 13.39% in 2024 and by 15.41% and 20.58% in 2025, respectively, and enhanced maize Pn, Tr, and Gs at the V12 and R1 stages. Soybean showed greater sensitivity to intercropping, with reduced SPAD values, Pn, Tr, and Gs during the branching, flowering, and pod-setting stages, whereas biochar application partially alleviated these inhibitory effects. Intercropping increased maize kernel number per ear and thousand-kernel weight but reduced soybean effective plant density, grain number per plant, and grain yield. Biochar application improved the grain yield of both intercropped maize and soybean. Under biochar application, the LER values reached 1.04 in 2024 and 1.21 in 2025, indicating a clear advantage in land-use efficiency. Overall, biochar application and maize–soybean intercropping were associated with improved photosynthetic performance, higher land-use efficiency, and increased system productivity.

Maize (Zea mays L.) is a major cash and food crop in China and is critical to national food security. Straw returning improves soil physical properties by reducing bulk density and increasing porosity, while phosphate fertilization enhances soil P availability; their combined application can improve soil fertility and structure, creating favorable conditions for high yield. To evaluate this, we conducted a three-year field experiment (2023–2025) in the Tumochuan Plain irrigation area (Midwestern Inner Mongolia, China) with maize cultivar ‘Xianyu 335’. A control treatment (CK) without straw management and without phosphate fertilization was included for comparison. We examined the effects of two straw management practices (straw incorporation with deep tillage, SF; and surface straw mulching under no tillage, FG) and four phosphate fertilization rates (0, 80, 100, and 120 kg P₂O₅/ha) on photosynthetic characteristics, chlorophyll fluorescence, dry matter accumulation, and yield. S and P main effects were significant for all measured traits, including Fo; however, the S × P interaction was not significant for Fo, Fm, Fv/Fm, Ci, and yield. Compared with CK, all straw management treatments improved photosynthetic and chlorophyll fluorescence traits, increased dry matter accumulation, and enhanced grain yield. Straw incorporation with deep tillage consistently outperformed surface straw mulching under no tillage, and increasing phosphate fertilization rates enhanced the positive effects. Among the tested treatments and under the partial-budget assumptions, SFP120 (120 kg P₂O₅/ha) gave the highest yield (14,781.53 kg/ha), while SFP100 (100 kg P₂O₅/ha) had the numerically highest net profit (17,743.33 yuan/ha, ≈2546.17 USD/ha), 21.19 yuan/ha (≈3.04 USD/ha) above SFP120 (17,722.14 yuan/ha, ≈2543.15 USD/ha).