Impact of tillage management on the short- and long-term soil carbon dioxide emissions in the dryland of Loess Plateau in China

Soil carbon dioxide (CO2) emission from agricultural areas is a complex phenomenon with high temporal and spatial variability. Tillage practices can affect drivers of CO2 production and therefore influence emissions by soils. However, the impact of tillage management on CO2 emissions from soil is uncertain due to specific climate and soil characteristics. A field experiment was initiated in 1992 in Shanxi, China including the no-tillage plots with straw mulching (NT) and conventional-tillage (CT) treatment. In 2012, another treatment (NTO) was conducted during which the straw was not returned to the plots when the winter wheat harvested. The CO2 emissions, soil temperatures and soil moisture content were measured during the fallow and wheat-growing periods from 2013 to 2015. Results showed that the rate of CO2 emissions was significantly higher immediately after tillage operation in the CT treatment. The annual CO2 emission rate in the NT treatment was significantly greater than that in the CT and NTO treatments (P < 0.05). For different season, the highest CO2 emissions rate occurred in summer (0.20 g CO2-C m(-2)h(-1)) while the lowest CO2 emissions rate occurred in winter (0.04 g CO2-C m(-2)h(-1)). These rates were only positively correlated with the soil temperatures (P < 0.05) and not significantly correlated with the soil moisture contents. Our results indicated that NT farming practices demonstrated increases CO2 emissions from soil compared with the CT and NTO treatments under dryland cropping system.