Objective  To clarify the effects of different interaction factors (aboveground interaction, root competition, soil environment improvement) on crop-yields under maize and legumes intercropping systems.

  Method  Maize/soybean and maize/peanut were intercropped with no separation, with a net-barrier or with a physical barrier to completely separate the involved maize and legume plants. In addition, maize, soybean, and peanut were also planted as monocrop at the testing fields for comparison. Interspecies competition or synergy, such as the aboveground plant interactions and underground root competition, and soil improvements induced by the treatments on crop-yields of the two systems were analyzed.

  Result  Intercropping maize and legume plants increased the combined crop-yield over the monocropping, despite the treatment differences. In an intercropping system, maize was most competitive of the 3 crops with respect to the aboveground growth, while peanut the least. The maize yield under the maize/soybean system increased with a contribution rate of 15.83% by the aboveground interactions, and 15.98% under the maize/peanut cultivation. The peanut yield, meanwhile, was suppressed by 11.42% when intercropped with maize. In contrast to the aboveground plant interactions, the root competition exerted negative effects on the yields of both species under the maize/soybean system that resulted in a reduction of 2.87% on maize, 5.35% on soybean, and 4.52% on total yield. For the intercropped maize and peanut plants, the root competition raised the maize yield by 5.88% and 0.8% on the combined yield. The intercropping improved soil conditions that facilitated crop-yield and production stability in both systems.

  Conclusion  The morphology and physiology of the maize, soybean, and peanut plants appeared to cause the variations on the effects on crop-yield by the intercropping. Meanwhile, the soil eco-system was improved by the practice contributing significantly to the yield and production stability. A quantified relationship between intercropping and crop-yield as illustrated by this study could be applied to optimize other agricultural planning and management as well.