RESUMO
Intercropping is a sound eco-agriculture model, but aquatic crops (e.g., rice) intercropping is seldom researched. In the present study, rice and water spinach were chosen as the research objects, a field trial was conducted to explore the yields, interspecific relationship and Si, N nutrition of rice under rice-water spinach intercropping for four seasons during two consecutive years (2014-2015). The experiment had five treatments: rice monoculture, water spinach monoculture, and rice-water spinach intercropping ratios of 2:2, 3:2, 4:2, respectively. The results showed that rice-water spinach intercropping significantly increased rice yield, and the increase rates of 2:2, 3:2 and 4:2 intercropping per unit area were 77.5%-120.6%, 64.9%-80.9%, 37.7%-56.0%, respectively. However, intercropping resulted in reduction of water spinach yield. Intercropping significantly increased total yield of rice and water spinach from land equivalent ratios (LER) analysis. The values of LER were more than 1.0, and the ratio of 3:2 intercropping had the best effect. As for the competitive index, rice was more competitive than water spinach in intercropping system, especially in early season. Compared with rice monoculture, rice-water spinach intercropping significantly increased the absorption of Si and N in rice leaves, and Si content of rice leaves during ripening stage, but didn't increase its N content and even slightly reduced it during ripening stage. Intercropping had no significant effect on available Si, ammonium N and nitrate N content in soil. Compared with rice monoculture and intercropping, water spinach monoculture had always the highest available Si, ammonium N and nitrate N contents in soil through the experiment period. The results suggested that rice-spinach intercropping could promote rice to absorb silicon and nitrogen and increase the competitive ability of rice.