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

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. 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. 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. 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. 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. Optimizing the intercropping spatial configuration represents a promising strategy for developing ecologically sound and high-quality forage cropping systems, which holds great significance for the sustainable development of agriculture in the Yangtze River Basin and beyond. • Intercropping spatial configurations enhanced forage yield, LER, and economic benefits. • Intercropping increased N, P, K accumulation by improving soil quality. • The spatial configuration increased RUE through the optimization of canopy structure. • The higher RUE and accumulation of N, P, K resulted in the overyielding of various intercropping configurations. • The 2:1 spatial configuration achieved the highest productivity and economic advantages.