The Qiyang Red Soil Station of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) has made significant progress in studying the regulatory mechanism of soil moisture conditions on greenhouse gas emissions from long-term fertilized rice paddy soil. The related findings, titled "Impact of soil moisture regimes on greenhouse gas emissions, soil microbial biomass, and enzymatic activity in long-term fertilized paddy soil", have been published in the journal "Environmental Sciences Europe".

Greenhouse gas emissions from farmland have always been a hot topic, with soil moisture and fertilization practices being important factors affecting the emissions of CH₄ and N₂O from soil. However, the changes in soil microbial biomass stoichiometry and enzymatic activity of paddy soil under different long-term fertilization conditions and soil moisture levels, and their relationship with greenhouse gases (CH₄ and N₂O) and soil properties, remain unclear. To address this, the study is based on a long-term field experiment with organic and inorganic fertilizer application initiated in 1982 at the Qiyang Red Soil Station. The study selected treatments of long-term sole inorganic fertilizer application, long-term sole organic fertilizer application, and combined organic and inorganic fertilizer application, with two different soil moisture conditions: 60%WFPS (percentage of soil volume water content to total pore space) and flooding, to investigate the effects of soil moisture conditions on CH₄ and N₂O emission fluxes, microbial biomass stoichiometry, and enzymatic activity.

The research results indicate that soil moisture is a crucial factor influencing greenhouse gas fluxes, soil nutrient availability, and activity. The N₂O emission from flooded soil is lower than that from 60%WFPS, while CH₄ emission is higher. The long-term combined organic and inorganic fertilizer treatment shows higher emissions compared to sole inorganic or organic fertilizer applications under both moisture conditions. Compared to 60%WFPS, the dissolved organic carbon (DOC) in flooded treatments increased by 15%-27%. The microbial biomass carbon, nitrogen, and phosphorus (MBC, MBN, MBP) in flooded treatments increased significantly by 8%-12%, 14%-21%, and 4%-22%, respectively. Soil moisture conditions have a certain impact on urease, with urease in flooded soil significantly higher by 42%-54% compared to non-flooded soil, while the effects on β-glucosidase and acid phosphatase are minor. DOC, MBC, pH are positively correlated with cumulative CH₄, and DOC is significantly positively correlated with cumulative N₂O. Soil moisture, MBC, DOC, pH, and enzymatic activity are identified as the most important factors influencing greenhouse gas emissions. PLS-PM analysis indicates that soil properties and enzymatic activity have a significant direct impact on CH₄ and N₂O emissions, while soil microbial biomass has an indirect positive influence on CH₄ and N₂O emissions. This study provides a theoretical basis for reducing greenhouse gas emissions in rice paddies in red soil areas by regulating soil moisture.

Asad Shah, a doctoral student at IARRP, and associate researcher Huang Jing are co-first authors, with researcher Zhang Huimin as the corresponding author. The research was supported by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, and the Jiangxi Province Science and Technology Special Project for Agricultural High-Tech Zones.

Paper Link: https://doi.org/10.1186/s12302-024-00943-4