Abstract: Change in landuse type is a key factor affecting the contents and dynamics of soil organic carbon (SOC). The understanding of the characteristics of SOC contents under various landuse types at farmland in Dongting Lake Region is essential to make judicious landuse policy and maintain land productivity. By investigation, sampling and laboratory analysis, the SOC contents at four typical landuse types (including dryland, flood drought rotation land, single cropping paddy field and double cropping paddy field) at farmland in Dongting Lake Region were studied. The results showed that the difference in the SOC contents at any two landuse types was highly significant (P < 0.01) and the SOC contents order was: double cropping paddy field (28.12 g/kg) > single cropping paddy field (27.03 g/kg) > flood drought rotation land (24.79 g/kg) > dryland (17.96 g/kg). It is illustrated that the land productivity, amount of straw returning and soil hydrological condition were main factors determining the differences in the SOC contents at various landuse types. The results further revealed that improving amount of straw returning, increasing in plant cropping, strengthening mulch on soil surface can maintain, and even enhance the SOC contents, especially at dry farming land in Dongting Lake Region.

Key words: landuse types, soil organic carbon, straw returning, cultivated soil, Dongting Lake Region