| A micro plot experiment and a root barrier technique were employed to investigate the intercropping advantage and the relative contribution of aboveground and under-ground interactions to the yield and nutrient uptaking in the wheat-maize intercropping system with or without plastic sheet mulching.The results showed that the land equivalent ratios(LERs) of both grain yield and biomass were 1.30 and 1.29 respectively for the intercropping of wheat and maize without plastic sheet mulching,showing a evident yield advantage of the intercropping.However,LERs with plastic sheet mulching were 1.41 for grain yield and 1.40 for biomass,indicating a significant yield advantage of the intercropping.There was evident advantage of nutrient uptaking in the intercropping of wheat and maize without plastic sheet mulching,whereas there was greatly significant advantage of nutrient uptaking in the intercropping with plastic sheet mulching.The contributions of above-ground and under-ground interactions to the intercropping advantage of both grain yield and biomass were 75% and 25% respectively for the intercropping without plastic sheet mulching.However,results of both grain yield and biomass were 67% and 33% respectively for the intercropping with plastic sheet mulching.The contribution of above-ground and below-ground interactions to the increase of nutrient uptaking were 67% and 33% for nitrogen,67% and 33% for phosphorus,50% and 50% for potassium respectively when intercropped maize was not mulched with plastic sheet.However,results of nutrient uptaking were 50% and 50% for nitrogen,55% and 45% for phosphorus,50% and 50% for potassium respectively when intercropped maize was mulched with plastic sheet. |