Spatiotemporal complementarity synergistically drives high productivity in intercropping systems: a comparison of...

Intercropping is an important planting pattern for improving land use efficiency. However, current research and practical applications focus mainly on the performance of the main crop and overall system yield, while neglecting the growth constraints on companion crops, which are often weaker competitors. This oversight contributes to critical challenges in intercropping systems, including imbalanced interspecific competition and substantial yield losses in companion crops. We conducted a three-year field experiment in the semi-arid rainfed agricultural region of northern China. We evaluated the productivity (crop yield, land equivalent ratio [LER], net effect), interspecific competition characteristics (competitive ratio, aggressivity), and economic benefits of the two intercropping systems: grain maize/soybean (GM/S) and fresh maize/soybean (FM/S). A central objective was to elucidate yield compensation response of subordinate soybean and the regulatory mechanism underlying balanced interspecific competition. Our results demonstrated that, averaged over three years, compared with theoretical sole cropping yields, intercropping increased grain maize and fresh maize yields by 25.97% and 17.29%, respectively, but reduced soybean yield. The FM/S system outperformed GM/S; under their optimal configurations, FM/S achieved 3.36% higher LER, and 11.42% higher economic benefits. The main crop was competitively dominant in both systems, but with different intensities: grain maize in GM/S exerted strong competition against soybean (mean CR = 2.07, A = 0.62), whereas fresh maize in FM/S showed milder competition (mean CR = 1.43, A = 0.34). By optimizing spatial configuration and shortening the co-growth period, FM/S improved yield compensation response of subordinate soybean, reducing its mean yield loss to 16.07%-significantly lower than the 37.32% loss in GM/S. Our results suggest that the FM/S intercropping system improves the yield compensation response of subordinate soybean, while enhancing system level complementarity effect (CE). Our observations highlight the combined roles of spatial configuration optimization and temporal niche differentiation, which show distinct advantages over conventional patterns that rely merely on the selection effect. These findings provide an important scientific basis for the optimization, upgrading, and large-scale application of cereal-legume intercropping systems in northern China. We recommend that fresh maize-soybean intercropping be prioritized for promotion in semi-arid rainfed agricultural regions.