Macropore structure and water management affect greenhouse gas emissions in agricultural fields

The process of greenhouse gas (GHG) emission processes is substantially affected by soil factors. Here, an intensive experiment was conducted to observe the effects of pore structure and water management on agricultural soil GHG emissions, total soil carbon, and nitrogen. Masa and paddy soils were prepared with/without macropores and with/without compost application. The Masa soil was exposed to unsaturated/saturated conditions, whereas the paddy soil was exposed to flooded conditions with/without drainage. CO2 emission from the Masa soil with macropores was higher than that from the Masa soil without macropores due to enhanced gas emission pathway. Total carbon (TC) was relatively lower in the top soil than in the bottom soil under non-flooded conditions, indicating CO2 emission from the top soil. Contrarily, TC was relatively lower in the bottom soil than in the top soil under flooded conditions, showing CO2 and CH4 emission from the bottom soil. Furthermore, the paddy soil with macropores showed higher CO2 emission than the soil without macropores. However, CO2 and CH4 emissions were lower with drainage application than without drainage in soils when macropores and compost were applied. The CH4 concentration negatively correlated with the infiltration rate, indicating that fresh water or oxygen was available in the soils with macropores and drainage. The TC and TN concentrations were lower in the bottom soil than in the top soil, suggesting the development of reductive conditions in soils without drainage. The findings showed that macropores reduced reductive conditions, thereby lowering CH4 emission.