Water mimosa (Neptunia oleracea Lour.) can fix and transfer nitrogen to rice in their intercropping system

BACKGROUND: Cereal–legume intercropping systems are an environmentally friendly practice in sustainable agriculture. However, research on the interspecific interaction of nitrogen (N) between rice and aquatic legumes has rarely been undertaken. To address this issue, a pot experiment was conducted to investigate N utilization and the N interaction between rice and water mimosa (Neptunia oleracea Lour.) in an intercropping system. The root barrier patterns consisted of solid barrier (SB), mesh barrier (MB), and no barrier (NB) treatments. The N fertilizer application rates were low, medium, and high N rates. RESULTS: The results showed that the NB treatment better facilitated rice growth compared with the MB and SB treatments. And the nitrate N content and urease activity of rice rhizospheric soil in the NB treatment were the highest of the three separated patterns. The ammonium N content in water mimosa rhizospheric soil and N₂ fixation of water mimosa ranked as NB > MB > SB. CONCLUSIONS: The amount of N fixation by water mimosa was 4.38–13.64 mg/pot, and the N transfer from water mimosa to rice was 3.97–9.54 mg/pot. This can promote the growth of rice and reduce the application of N fertilizer. We suggest that the rice–water mimosa intercropping system is a sustainable ecological farming approach and can be applied in the field to facilitate rice production.