No-tillage with total green manure mulching reduces soil respiration by regulating soil moisture affecting heterotrophic respiration

Background and aims Green manure is widely used in agricultural production due to its beneficial soil modification and fertilization functions. However, the mechanisms related to the effects of green manure return methods on soil respiration (Rs) and its components are not clear. The aim of this study was to investigate the effect of green manure return methods on Rs in maize fields by quantifying Rs. Methods A field experiment with five treatments was conducted in 2021–2023 in the inland river oasis irrigation area of Gansu: tillage with a full quantity of green manure incorporated into the soil (TG), no-tillage with a full quantity of green manure mulched into the soil surface (NTG), tillage with roots incorporated into the soil and above ground green manure removed (T), no-tillage with above ground manure removed (NT) and conventional tillage and leisure (CT). Results The results showed that compared to CT, the NTG treatment increases maize grain yield while reducing Rs by 6.7–8.7%, carbon emission (CE) by 6.7–8.6%, and improving carbon emission efficiency (CEE) by 20.8–25.6%. The increase in soil water content (SWC) significantly reduced soil heterotrophic respiration rate (Rh) during all growth periods, which was the main reason for the decrease in Rs. Additionally, under this treatment, the NEP-C of the farmland ecosystem is positive, indicating that the soil acts as a carbon "sink". Conclusions Therefore, no-tillage with full quantity of green manure mulched on soil surface is an effective measure for carbon sequestration and emission reduction in farmland.