Soil conservation tillage practices such as no-tillage and straw mulching are of great significance for saving energy input in farmland, mitigating greenhouse gas emission to the atmosphere, and increasing carbon sequestration potential in soils. Despite of great interest in the effect of no-tillage (NT) management practice on carbon sequestration and GHG emissions in northern China, long-term effects of different tillage practices in that region on farmland system carbon footprints remain unclear. Based on a 20-year conservation tillage experiment in a winter wheat system at Linfen City in Shanxi province, we evaluated long-term (20-year) effects of NT and conventional tillage (CT) practices on the carbon balance. During the experiment, we measured soil respiration and soil carbon concentration in the field. A random block design with three replications was used to assess both the tillage and its effects on soil carbon sequestration and yield of winter wheat ( Triticum aestivum L.). Production, formulation, storage, and distribution of these inputs such as seed, chemical fertilizer and application with tractor equipment cause the combustion of fossil fuel and use of energy from other sources, which also emits CO 2 and other GHGs into the atmosphere. Thus, it is essential to understand emissions in kilograms carbon equivalent (kg CE) of various tillage operations, fertilizers, pesticides, harvesting and residue management. The index of carbon emission of different agricultural inputs were taken from literatures. In our study, carbon emission produced by chemical fertilizer with NT and CT practices accounted for 73.3%-77.1% of total carbon emission from agricultural inputs, and has become the main carbon source. Compared with other countries, fertilizer input in China accounts for a greater portion within agricultural production, and fertilizer costs made up about 50% of total costs in china. Reducing fertilizer use is an effective means to decrease indirect carbon emission. Because NT reduced moldboard ploughing, chisel ploughing and stover removal, carbon emission from agricultural inputs under NT was 5.1% less than that under CT. Moreover, T. aestivum L. yield with NT treatment increased by 28.9% over CT treatment. Carbon productivity in the NT system was greater than that in CT. After 20 years, SOC concentration in NT soil was greater than that in the CT soil, but only in the layer between 0 and 10 cm. There was significant SOC accumulation (0-60 cm) in the NT soil (50.86 Mg/hm 2) compared with that in the CT soil (46.00 Mg/hm 2). The total CO 2 flux of soil respiration under NT was greater than that under CT. However, according to a carbon balance analysis, NT acted as a carbon sink compared to CT as a carbon source. This favored carbon sequestration in the farmland system. Therefore, long-term NT practice can increase soil carbon sequestration and reduce GHG emissions. The carbon emission coefficients are from literatures and N 2O emission is not considered in the study. These may affect the results, but the trend among the different tillage system remains unchanged. With the improvement of the parameters, the accuracy of the assessment can be further improved. NT can be a significant innovation for carbon-friendly agricultural production technology in Northern China, because of its savings of energy/labor/time, reduction of GHG emissions, and benefits of SOC sequestration.
