Subsoiling reduces CO2 concentrations in soil profile of winter wheat - summer maize rotation ecosystem in the North China Plain: a strategy to achieve carbon neutrality in farmland

Reducing CO2 emissions from agricultural soils is a key component of the overall carbon reduction strategy. The closed chamber method was used to continuously monitor CO2 concentration in soil profiles of winter wheat-summer maize rotation fields in the North China Plain (NCP) during 2015-2017. Additionally, we evaluated the contribution of different tillage methods (Rotary tillage (RT), Subsoiling (SS), No- tillage (ZT), and conventional tillage (CT) in combination with Straw return (s) and straw removal (0)) to reducing soil CO2 emission. The results showed that the concentration of CO2 increased with the soil depth and peaked at the 150 cm layer. The trend of CO2 concentration in soil profiles under different tillage treatments was CTS > RTS > ZT(S) > SSS, and the average concentration in maize season was higher than that in wheat season. In addition, soil moisture and temperature in the 0-10 cm soil layer were significantly correlated with soil CO2 concentrations. Thus, our results highlight that the SSs plays a critical role in moderating soil CO2 emissions. This process merits further study to effectively regulate soil CO2 release and achieve carbon neutrality with less carbon emissions in farmland ecosystems.