Effect of Chinese milk vetch (Astragalus sinicus L.) as a green manure on rice productivity and methane emission in paddy soil

This field study was undertaken to investigate the optimum recycling rate of the above ground biomass of Chinese milk vetch (Astragalus sinicus L. hereafter, vetch) to improve rice productivity and decrease seasonal methane (CH₄) flux in mono-rice cultivation system. The above ground part of vetch was applied in paddy field at rates 0, 10, 20 and 40Mgha⁻¹ on fresh weight basis to investigate its effect on rice (Oryza sativa) productivity and CH₄ emission flux and was compared with the typical standard NPK chemical fertilization (N-P₂O₅-K₂O=90-45-58kgha⁻¹). Rice productivity increased significantly with increasing vetch application, and more interestingly, similar grain yield was obtained between vetch application at 10Mgha⁻¹ as green manure and NPK fertilization. Methane emission rates, which were measured by closed-chamber…