Legume/cereal intercropping can improve nitrogen (N) use efficiency and crop yields.Numerous attempts have been made to examine effects of legume-cereal intercropping patterns in upland and dry fields.However,the rice-legume intercropping in irrigated farming systems remains to be investigated.In this study,a field experiment was conducted to evaluate the effects of rice-water mimosa (Neptunia oleracea) intercropping patterns on crop yield,N uptake,and soil N content dynamics at an irrigated farm located in Southern China.Four cropping patterns,namely,(1) Rice monocropping with conventional N input (CK,N was applied at the level of 180 kg·hm-2);(2) Rice monocropping with low N input (LRM,N was applied at the level of 140 kg·hm-2);(3) Water mimosa monocropping (NOM,N was applied at the level of 140 kg·hm-2);And (4) rice-water mimosa intercropping (LRN,N was applied at the level of 140 kg·hm-2) were,respectively,used for late rice in 2014 and early rice in 2015.Results showed that tiller number,leaf area index and above-ground biomass were significantly increased for the LRN pattern as compared to those for the CK and LRM patterns.Among the cropping patterns,tiller number,leaf area index,above-ground biomass and grain yield of rice at the edge rows (adjacent to water mimosa) were significantly higher than those at the inner rows.The rice yield was in the following order:LRN＞CK＞LRM.The unit land area yield of water mimosa (based on the planted area) for the LRN pattern was lower than that for the NOM pattern.The land equivalent ratios calculated based on the NOM,LRN and CK patterns were 1.01 for late rice in 2014 and 1.2 for early rice in 2015,whereas the land equivalent ratios calculated based on the LRN,NOM,and LRM patterns were 1.12 for late rice in 2014 and 1.25 for early rice in 2015.The rice yield for the LRN pattern as compared to the CK increased 20.2％ in 2014 and 35.3％ in 2015,indicating that intercropping promoted crop yield per unit land area.The total N uptake amount of rice population was significantly lower for intercropping than for mono-cropping.After planting for two seasons,the soil total nitrogen (TN) content for the LRN pattern increased 0.21％ as compared to that of CK pattern and increased 1.69％ as compared to that of LRM pattern.These results suggested that rice-water mimosa intercropping can maintain a higher land equivalent ratio and enhance crop yield and soil TN content under lower N input.%豆科与禾本科作物间作有利于提高氮素利用率及作物群体产量.旱地条件下豆科与禾本科作物间作产量优势的研究已多见报道,但水田环境下水稻(Oryza sativa)与豆科水生作物间作模式的研究报道甚少.在华南地区水田条件下分别构建了2015年晚稻和2015年早稻水稻与水合欢(Neptunia olerace)间作模式,并探讨该模式对产量和稻田土壤氮素的影响.试验设常规施氮水稻单作(N 180 kg·hm2,CK)、低氮水稻单作(N 140 kg·hm-2,LRM)、水稻-水合欢间作(N140 kg·hm-2,LRN)和水合欢单作(N 140 kg·hm2,NOM)4种处理,测定不同种植模式下的作物产量、吸氮量、土地当量比及稻田土壤全氮含量的变化.结果表明,间作栽培模式下的水稻茎蘖数、叶面积指数和地上部生物量均显著高于CK和LRM,其中与水合欢相邻的边行水稻茎蘖数、叶面积、地上部生物量和产量均显著高于内行.水稻实地面积产量表现为LRN＞CK＞LRM,LRN处理下水合欢实地面积产量低于NOM.2014年晚稻和2015年早稻,以LRN、NOM和CK计算的土地当量比分别为1.01和1.20,以LRN、NOM和LRM计算的土地当量比分别为1.12和1.25,表明间作模式下作物整体产量明显提高.LRN处理下水稻群体总吸氮量显著低于CK和LRM,经过两季种植后,LRN处理下土壤全氮含量分别比CK和LRM提高了0.21％和1.69％.在水田环境中,水稻与水合欢间作在低氮投入下能维持较高的土地当量比,且提高了作物群体产量和土壤全氮.
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