Investigation on the feasibility of straw incorporation to improve soil fertility without obviously increasing global warming potential

Abstract. The utility of rice straw as an organic fertilizer has been widely recognized as a promising approach to enhancing soil fertility. However, straw return is currently in a dilemma, as it may also provoke greenhouse gas (GHG) emissions, leading to serious environmental consequences. It is urgent to reveal the feasibility of straw incorporation regarding soil fertility improvement without notable increases in GHG emissions. Here, a soil microcosm experiment was employed to investigate the relationships between soil fertility and GHG fluxes and the underlying mechanisms influenced by straw amendments. Paddy soils were collected from a long-term rice straw incorporation field experiment. The dynamics of GHG fluxes and concentrations in soils, and the variations in the abundances of soil microbial communities were systematically determined. The results indicated that continuous rice straw incorporation at half of the harvest (ST1) obviously improved soil fertility but did not induce significant elevation of global warming potential (GWP). The minimal increase in GWP was mainly attributed to the significant reduction in N₂O emission and the slight rise in CH₄ emission compared to straw removal. The main mechanisms for these consequences were that ST1 possessed the highest nosZII abundance and the lowest nirS/nosZII ratio; meanwhile, its CH₄ production ability fluctuated around the soil CH₄ holding capacity, and most of the produced CH₄ was consumed by methanotrophs. In conclusion, rice straw can be incorporated into paddy soils at a suitable application rate, which can effectively enhance soil fertility without inducing an additional warming effect.