Abstract:

Aims Optimization of resource structure is important for improving the yield of intercropping systems. Our objective was to clarify the contribution of above- and below-ground interactions to the intercropping advantage.
Methods We employed a micro-plot experiment and root barriers in a wheat-maize intercropping system with or without maize plastic sheet mulching.
Important findings Non-plastic sheet mulching wheat-maize intercropping system has a yield advantage with land equivalent ratios (LERs) for grain yield and biomass of 1.30 and 1.29, respectively. Plastic sheet mulching with maize can significantly increase the yield advantage of intercropping, with LERs for grain yield and biomass of 1.41 and 1.40, respectively. There is increased nitrogen, phosphorous and potassium uptake in the non-plastic sheet mulching wheat-maize intercropping and with plastic sheet mulching with maize. In the non-plastic sheet mulching intercropping system, the relative contribution to the intercropping advantage is 75% above-ground and 25% below-ground, but in the plastic sheet mulching intercropping system it is 67% above-ground and 33% below-ground. The relative contribution of above- and below-ground interactions to nutrient advantage are 67% and 33% for nitrogen and phosphorus and 50% and 50% for potassium, respectively, in non-plastic sheet mulching intercropping; however, plastic sheet mulching with maize can increase the below-ground contribution to nitrogen and phosphorus advantage in the intercropping (there is no significant influence to potassium advantage). Intercropping advantage can be obtained by crop matching and controlled by plastic sheet mulching. Plastic sheet mulching with maize can significantly increase yield advantage, nutrients absorption advantage and the below-ground contribution.

Key words: wheat-maize intercropping, intercropping advantage, above-ground interaction, below-ground interaction, relative contribution