Abstract:Scientific regulation of both energy and carbon flows under tillage system with soil conservation tillage practices is of great significance for saving energy input in farmland, mitigating greenhouse gas emission to the atmosphere, and increasing carbon sequestration potential in soils. Based on the field experimental studies on conservation tillage in dryland maize cropping systems, located in Shouyang Dryland Farming Station in Shanxi province of China, impacts of different tillage systems (including conventional tillage (CT), reduced-tillage (RT), and no-till (NT) practice) on coupled energy/carbon balance were integrally studied. through field observations, embodied energy input parameter determinations, soil respiration measurements, carbon dynamic processe simulations, and energy/carbon balance estimations in dryland agro-ecosystems. Compared with CT, conservation tillage (RT and NT) could increase carbon input (about 1.6 tC · hm-2) with increasing stover return and root stubble biomass in the soils, but reduce carbon losses by stover burning/or removal (about 1.6 tC · hm-2) and by soil erosion (about 1.2-1.6 tC · hm-2). The energy inputs (MJ · hm-2) were in the order: CT(13829) >RT(13289) >NT(12434), which was similar to the order for carbon emissions (kgC · hm-2): CT(283) >RT(272) >NT(248). The embodied energy consumption was reduce by about 4%-12% (equivalent to 11-35 kg CO2-C · hm-2 · a-1) with NT and RT practices, as compared to the CT practice. The coefficiency of energy consumption was decrease by about 6%-10% and the coefficiency of energy production increase by 7%-12% under conservation tillage systems, as compared to the CT practice. The results also showed that the rates of soil organic carbon sequestration (kg C · hm-2 · a-1) tended to increase from -104 with CT to 144-149 with NT and RT. The field measurements during periods 2006-2007 showed that the mean soil respiration rates (kg CO2-C · hm-2 · a-1) with NT were generally lowest (-13%) during the fellow periods in the order: NT (540±30) 2-C · hm-2 · a-1) were RT (2342±524) >NT (2005±380) >CT (1987±375). The changes in maize grain yields showed the same trend with soil respiration associated with tillage practices, for instance, the mean maize grain yields (kg · hm-2 · a-1) also were RT (5614±1298) >NT (5533±631) >CT (5487±1320), showing a positively close relationship between maize grain yields and soil respiration during growing stage (R2=0.88). Although different methods were used to estimate CO2-C emissions by soil respiration processes, the analysis showed the same trends in carbon sink/source under tillage systems, such as a increasing trend in carbon sink with conservation tillage practices (generally RT >NT) compared to carbon source with CT, indicating that stover incorporation combined with conservation tillage practices through increasing carbon input is an effective way for maintenance and enhancement of soil organic carbon.