Co-incorporation of rice straw and green manure with reduced nitrogen fertilizer application maintained rice yield and lowered ammonia volatilization

Aims: Co-incorporation of rice straw (RS) and green manure (GM) is an effective practice for replacing nitrogen (N) fertilizer and lowering reactive N losses to the environment. This study aimed to determine the effects of incorporating RS and/or GM with 40% reduction in N fertilizer application on ammonia (NH) volatilization and rice N uptake. Methods: A 3-year field trial with six treatments was established: no N fertilizer (N0), 60% of conventional N fertilizer application rate (N60), N60 with RS (SN60) or GM (MN60) incorporation alone, N60 with co-incorporation of RS and GM (SMN60), and 100% of conventional N rate (N100). Results: Similar rice grain and straw yields, N uptake and applied N recovery efficiency were obtained by the treatments of MN60, SMN60, and N100. Compared with N100, all other treatments significantly lowered NH fluxes, primarily due to the lower NH-N concentration and pH in the surface water. The cumulative NH volatilization from the MN60 and SMN60 treatments was decreased by 24.2%-57.0% and 13.6%-41.1%, respectively, compared with that in N100 treatment. The SN60, MN60 and SMN60 treatments resulted in a lower loss rate of applied N through NH volatilization than N60 and N100. Furthermore, the incorporations of RS and/or GM could enhance the concentration of soil organic matter, total N, and NH-N. Conclusions: This study suggests that replacing 40% of conventional N fertilizer input by co-incorporation of RS and GM can maintain rice yield and N uptake and lower NH volatilization.