Tillage and residue management affect growing-season soil respiration in paddy fields

Abstract

Farmland soil respiration (SR) plays a pivotal role in affecting global carbon (C) cycling. To examine impacts of paddy management (including tillage and residue management) on growing-season SR, four long-term treatments were established: conventional tillage with residue mulching (CTM), conventional tillage with residue removal (CT), reduced tillage with residue mulching (RTM), and reduced tillage with residue removal (RT). All treatments lasted for six years starting on October 19th, 2014. Since the growing season is May to October, the measurements were performed from May 8th to September 30th, 2020. In-situ measurements were made of SR, and corresponding soil samples were collected and analyzed for soil texture, soil nutrient, soil organic carbon (SOC), C composition, and soil microbial abundance. Results showed that four treatments had a significant difference in terms of growing-season SR. The cumulative SRs of CT, CTM, RT, and RTM were 2.066, 2.502, 2.396, and 2.649 kg m-2, respectively. The observation was contrary to the conventional perspective that no-tillage with residue mulching leads to lower CO2 emissions. For soil microbial abundance, compared with CTM, RT, and RTM, CT had the lowest contents of total PLFA, bacteria, and fungi. In addition, CT had the lowest unstable C compositions, and the highest stable C compositions among all treatments. Redundancy analyses (RDA) indicated that cumulative SR increased with the increase of soil microbial abundance. Further, Pearson correlation analyses showed that cumulative SR had a positive correlation with unstable C characteristics and a negative correlation with stable C characteristics. The results suggested that CT is more conducive than the other three treatments in slowing the growing-season SR. This study provides novel insights regarding the impact of agricultural management on growing-season SR, which has practical significance for the management of agricultural lands in the context of carbon cycling.