Soil microbial biomass and greenhouse gas emission dynamics response to nitrogen rates under organically amended paddy soil

Rice paddy has been regarded as a unique ecosystem compared to other crops as rice is cultivated under highly saturated conditions for most growth stages. Its unique ecosystem selects for distinct microbial composition and abundance in response to the oxic-anoxic interface. Rice paddy is also known to be a significant source for greenhouse gas emissions (GHG) including CO₂, CH₄, and N₂O, the deleterious gases causing global warming. This study investigated the effects of N fertilization on the changes of soil microbial biomass and the changes of GHG in organic rice ecosystem.   Soil microbial biomass C and N were significantly affected by N application rates of organic soil amendments at heading stage and before harvest. The use of soil amendment at 150 kg N ha^-1was observed to promote higher total microbial biomass C and N than any other treatments. CO₂, CH₄, and N₂O weekly fluxes were significantly influenced by different N rates of organic soil amendments at 44, 54, and 70 days after planting. Higher global warming potential was stimulated by highest N fertilization (150 kg N ha^-1). The smallest GHG index was estimated in rice paddy receiving soil amendment at 150 kg N ha^-1.