Abstract: A microplot experiment and a root barrier technique were employed to investigate the intercropping advantage and the relative contribution of above- and below-ground interactions to the yield and nutrient uptaking in the barley-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 around 1 (average 1.06) for the intercropping of barley and maize without plastic sheet mulching, showing a yield disadvantage of the intercropping. In contrast, LERs with plastic sheet mulching were 1.32 for grain yield and 1.30 for biomass, indicating a significant yield advantage of the intercropping. There was no significant advantage of nutrient uptaking in the intercropping of barley and maize without plastic sheet mulching, whereas there was significant advantage of nutrient uptaking in the intercropping with plastic sheet mulching. The contribution of above-ground and below-ground interactions to the intercropping advantage of grain yield were 80% and 20%, respectively, for the intercropping with plastic sheet mulching. Similar results were observed for above-ground biomass. The contribution of above-ground and below-ground interactions to the increase of nutrient uptaking were 50% and 50% for nitrogen, 60% and 40% for phosphorus, 45% and 55% for potassium respectively, when intercropped maize was mulched with plastic sheet.

Key words: Barley-maize intercropping, Yield advantage, Above-ground interaction, Below-ground interaction, Relative contribution