Soil respiration, N2O, and CH4 emissions from an Andisol under conventional-tillage and no-tillage cultivation for 4 years

No-tillage (NT) management is a promising method to sequester soil C and mitigate global warming caused by agricultural activities. Here, we report 4 years of continuous soil respiration rates and weekly nitrous oxide (N2O) and methane (CH4) emissions in NT and conventional-tillage (CT) plots in a typical Japanese volcanic soil. Overall, the soil respiration, N2O emission, and CH4 uptake decreased significantly in the NT plot. A difference in soil respiration and N2O emission between the two plots began after the tillage treatment and the incorporation of crop residues and fertilizers, whereas the CH4 uptake did not vary significantly during the fallow period after the treatments. The N2O emission was higher from the CT than from the NT plot during the fall. The overall lower CH4 uptake in the NT than in the CT plot likely resulted from a combination of decreased soil gas diffusivity and higher mineral N content at the soil surface. Higher soil respiration and N2O emission occurred in the NT plot in the summer of 2003 and were plausibly caused by an increase in the soil moisture content that resulted from lower temperatures during July and August; the higher soil moisture must have accelerated the decomposition of organic matter accumulated in the topsoil. These results indicate that NT management is generally effective for the mitigation of the total GWP by reducing soil respiration and N2O emission in temperate regions; however, NT management may increase rather than decrease these emissions when fields experience cool summers with frequent rainfall.