Impact of soil moisture, rice straw, and nitrogen fertilizer on greenhouse gas emissions from agricultural soils

Soil moisture, carbon, and nitrogen are vital factors affecting greenhouse gas (GHG) emissions in agricultural soils. However, research on GHG dynamics across different soil moisture regimes, ranging from simultaneous flooding-to-upland conversion, transition phases, to continuous flooding, and their interaction with crop straw and nitrogen (N) fertilizer amendments remains limited. To address this research problem, we conducted a laboratory study to investigate the impact of water regimes, rice straw (Oryza sativa L.), and N fertilizer on GHGs. The addition of rice straw and fertilizer significantly increased GHG emissions. N₂O and CO₂ emissions increased as soil moisture levels were converted from flooded conditions to 60% water-filled pore space (WFPS), while CH₄ emissions decreased. The highest cumulative N₂O and CH₄ emissions were 0.85 mg N₂O-N kg^-1 and 65.21 mg CH₄-C kg^-1, respectively, in rice straw treatment, while cumulative CO₂ emissions were highest (2003.69 mg CO₂-C kg^-1) in rice straw + N fertilizer treatment. The NH₄ ⁺ and NO₃ ^- levels were highest with values of 202.43 and 63.72 mg kg^-1, respectively, in the rice straw + N fertilizer treatment during the transition phase. The highest levels of dissolved organic carbon (201.31 mg kg^-1) and microbial biomass carbon (425.92 mg kg^-1) were recorded in the rice straw treatments during the flooding and 60% WFPS phases, respectively. Our findings emphasize the critical role of soil moisture and organic amendments in regulating soil GHG emissions. Sustainable agricultural practices should focus on balancing soil management techniques to reduce GHG emissions while promoting long-term soil health.