Abstract: A microplot experiment and a root barrier technique were employed to investigate the yield advantage of relay intercropping and the absorption and utilization efficiency of nitrogen，phosphorus and potassium by the component crops relay intercropped or monocultured，and the relative contribution of above- and below-ground interactions to yield in the capsicum/maize relay intercropping system with or without nitrogen fertilizer application was also researched. The results showed that the land equivalent ratios（LERs）of both economic yield and biological yield exceeded 1，which demonstrated a significant yield advantage for all the relay intercropping treatments of capsicum and maize. The biological yield advantage was stronger than that of the economic yield advantage. The absorption of nitrogen，phosphorus and potassium by capsicum and maize in the intercropping system were 16.4%–22.1%，26.1%–30.5% and 27.0%–51.5% higher，respectively，than those in the monoculture system. However，the utilization efficiency of nitrogen，phosphorus and potassium in the intercropping system were 4.0%–14.1%，4.4%–9.4% and 4.3%–15.9% lower，respectively，than those in the monoculture system. The relay intercropping advantage on nutrient aspect was mainly due to the increase of nutrient absorption but not the decrease of nutrient utilization efficiency. The harvesting index of relay intercropping capsicum was significantly higher than that of the monocultured capsicum. The contribution of above- and below-ground interactions to the relay intercropping advantage of economic yield were 93.2% and 6.8%，respectively；Nevertheless the values were 88.8% and 11.2% respectively for biological yield in the condition of no nitrogen fertilizer application. While in the nitrogen fertilizer application zone，the contribution of above- and below-ground interactions to the relay intercropping advantage of economic yield were 85.2% and 14.8% respectively，and 84.6% and 15.4% were their relay intercropping advantage of biological yields respectively.

Key words: capsicum, maize, relay intercropping, yield advantage, nutrient utilization efficiency, above-ground interaction, below-ground interaction