Study on the Simulation of Soil Organic Carbon Content under Different Tillage Modes

During the past century decreases in soil organic carbon content and soil fertility have been widely observed in many agricultural regions.Maintaining farmland soil organic carbon content is essential for the sustainable development of Chinese agriculture.Dingxi County with typical inland agro-ecosystems was selected as a geographic domain for a modeling study reported in this paper.A process-based biogeochemical model DNDC(Denitrification Decomposition) was linked to a Geographic Information System(GIS) database holding spatially differentiated information of climate,soil,vegetation and management for Dingxi to quantify impacts of farming management alternatives on C sequestration in farmland of this region.DNDC was first validated against a long-term SOC dataset observed in Dingxi County in Gansu Province.Based on the feasibility of DNDC model in the hilly areas of the Loess Plateau,which was validated using database of a long-term experiments on different tillage practices in Dingxi experimental station of Gansu Agricultural University,continuous SOC changes and carbon cycle features under different tillage patterns were studied by using DNDC model.The results derived from four tested simulations for long-term periods(100 years) showed that SOC increased greatly in the treatments of no-tillage with straw cover and conventional tillage with straw incorporated,by 74.76% and 71.13% respectively;but in-creased gently in the treatments of no tillage with no strew cover by 39.18%.Sensitivity tests indicated that soil property especially initial SOC content was the major source of uncertainty generated from up scale modeling.The simulation of soil organic carbon content under different tillage modes showed that SOC can be increased depending on higher manure,higher proportions of straw returning.According to the simulating results of DNDC model on the hilly areas of the Loess Plateau,straw addition,fertilizer application or no-tillage will be an effective measure for maintaining improved soil fertility,increasing the amount of storage of the organic carbon pools in soil.