Responses of soil CO2 emissions to tillage practices in a wheat-maize cropping system: A 4-year field study

Context or problem: Soil CO2 emissions respond differently to different tillage practices. However, limited in-formation is available regarding the impact of conventional tillage (CT) and no-tillage (NT) on soil CO2 emissions and the primary controlling factors or processes.Objective or research question: The goal of this study is to derive the relationship of soil CO2 emissions with soil physicochemical properties from differently tilled soils in a typical winter wheat-summer maize rotation sys-tem. We hypothesized that soil tillage practices would impact the soil carbon cycle by modifying soil physical and chemical properties, which would in turn affect the soil CO2 emissions. Methods: The study was conducted from 2018 to 2022 with two tillage practices using a randomized complete block design with three replicates. A leading international real-time monitoring system in situ was used to collect soil CO2 emission data.Results: Cumulative soil CO2 emissions were reduced by 28.7% in maize and increased by 9.0% in wheat under NT as compared to CT. On an annual scale, the cumulative CO2 emissions were decreased by 20.5% in NT as compared to CT. Maize season accounted for 70%-78% of soil CO2 emissions. NT improved the aboveground biomass by 7.74% and 6.44%, and grain yields by 10.2% and 4.49% for maize and wheat, respectively. The soil CO2 emission intensity of maize was reduced by 35.9% under NT as compared to CT. No significant differences were discovered under the two tillage practices for soil CO2 emission intensity of wheat. For maize, NT increased the bulk density, subsequently decreasing soil temperature and increasing soil moisture. NT also led to higher soil organic carbon and total nitrogen content, ultimately resulting in a significant reduction in soil CO2 emissions. For wheat, NT increased soil bulk density, further increasing soil moisture and lowering soil pH. NT thus resulted in lower soil organic carbon and total nitrogen content, ultimately leading to enhanced soil CO2 emissions. Some of these observations might not be consistent with theoretical predictions, which indicated that the unconsidered factors of actual field conditions might have much significant effects.Conclusions: Overall, NT can be extensively used as an eco-friendly cropland tillage practice based on its positive effects of reducing CO2 emissions and increasing crop yields.