Effect of Green Manures on Rice Growth and Plant Nutrients under Conventional and No‐Till Systems

Alfalfa ( Medicago sativa L.) is a good green manure resource with high N and P concentrations, but its effect on rice ( Oryza sativa L.) growth and plant nutrients has not been fully elucidated. Two green manure species, alfalfa and broad bean ( Vicia faba L.), and two N fertilizer levels (0 and 200 kg ha −1 ), alone or in combination, were applied to rice paddy soil under conventional tillage (CT) and no‐till (NT) systems in 2010 and 2011. The results showed that, under CT, alfalfa had a more pronounced effect on increasing grain yield and nutrient content in the grain, plant (leaf N and leaf P), and soil (total N and Olsen P) than broad bean ( p < 0.05). Compared with the N fertilizer treatment, the alfalfa treatment alone achieved statistically equivalent levels of grain yield but significantly increased P contents in grain and leaf and Olsen P in soil. The leaf P concentrations at the panicle and grain filling stages had significant positive direct effects and indirect effects via leaf N concentration on grain yield. The effect of alfalfa green manure on the supply of available P to rice was equal between CT and NT systems. The combined treatment of alfalfa and N fertilizer achieved the highest grain yield of all treatments, increasing the yield under CT by 8.58 and 8.21% compared with the N fertilizer treatment in 2010 and 2011, respectively. These results indicate that green manure with a high P concentration is capable of alleviating P deficiency in both CT and NT rice cultivation systems.