Effects of soil warming and straw return on soil organic matter and greenhouse gas fluxes in winter wheat seasons in the North China Plain

As one of the greatest political and scientific issues, global warming is affecting the terrestrial carbon (C) and nitrogen (N) cycles and subsequently greenhouse gases (GHGs) fluxes. Straw return is considered as an environmentally friendly management to increase soil health and agricultural productivity. However, little is known about their interactive effects on soil organic matter (SOM) and GHGs emissions. Therefore, we collected two-year data from a field experiment in the North China Plain (NCP) to elucidate the effects of soil warming (ambient temperature vs. warming +3.8 °C) and straw management (straw removal vs. straw return) on soil properties, nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) fluxes during winter wheat seasons. Soil warming stimulated the available nutrients (NH4+, NO3−, and dissolved organic C), and thereby increased cumulative CO2 emission by 17.5–25.0% compared with ambient temperature, while had no effect on N2O fluxes. Straw return enhanced soil CO2 and N2O emissions by 11.5–28.3% and 37.1–48.4% compared with straw removal, respectively. This was mainly due to increased organic matter input stimulating microbial activity, thereby accelerating soil C and N cycling. The NCP was found to be a CH4 sink, and soil warming and straw return increased the CH4 uptake. Finally, soil warming combined straw return resulted in the highest GHGs budget, and we estimated that almost 7.1 t CO2-eq ha−1 per wheat season would be lost in response to soil warming and straw return in the NCP. In the second growing season, soil organic C (SOC) and total N (TN) were reduced under warming by 6.1% and 4.9% due to the stimulated decomposition and mineralization, respectively. However, the decreases considerably counteracted by straw return, which enhanced the SOC and TN by 5.8% and 9.4%, respectively. Our study suggested that soil warming and straw return will lead to stimulated GHGs emissions in wheat seasons in the NCP, while straw return may contribute to the mitigation of global warming through increasing SOM accumulation.