Diversified spatial configuration of rapeseed-vetch intercropping benefits soil quality, radiation utilization, and forage production in the Yangtze River Basin

Contexts: Intercropping facilitates agricultural sustainability and intensification by increasing crop diversity at the spatial scale. However, the spatial configuration of intercropped crops, which is essential for enhancing crop-soil interactions and ecological services to achieve increased productivity and efficiency, remains understudied. Objectives: We aimed to evaluate the effect of spatial configuration of hairy vetch/rapeseed intercropping on forage yield, economic benefits, and soil quality, and to elucidate the underlying mechanisms. Methods: Three different spatial configurations of intercropping including 2:1, 1:1, and 0.5:1 ratios of hairy vetch (with variable planting density and position) and rapeseed (with fixed density and position) were designed and investigated through a two-year field experiment, compared with rapeseed (SR, 0:1) and hairy vetch sole cropping (SH, 1:0). The evaluation criteria included forage yield, crude protein yield, soil characteristics, nutrient accumulation, radiation use efficiency (RUE), land equivalent ratio (LER), and economic benefits. Results: Intercropping rapeseed with hairy vetch showed significant competitiveness compared to rapeseed and hairy vetch sole cropping. Among the five systems evaluated, the 2:1 spatial configuration achieved the maximum biomass yield (18.4 Mg ha(-1)), net profit value (29,598.9 CNY ha(-1)), and LER (1.48) at the final flowering stage, followed by the 0.5:1 and 1:1 spatial configuration. Moreover, intercropping rapeseed with hairy vetch significantly increased soil available phosphorus (AP) and potassium (AK) content, as well as soil enzyme activity. However, it led to a significant decrease in soil pH compared to rapeseed sole cropping. Principal component analysis indicated a negative correlation between soil pH and AP, AK contents, while a positive correlation was observed between soil AP, AK contents and the accumulation of P and K in all intercropping configurations. Additionally, structure equation modeling analysis revealed that intercropping systems enhanced forage productivity by improving RUE and the total accumulation of N, P, K. Conclusions: In conclusion, rapeseed-hairy vetch intercropping, particularly the 2:1 spatial configuration could be considered a high-yield and high-quality winter forage intercropping system that alleviates forage shortages and promotes the development of herbivorous animal husbandry.