Irrigation regime affected SOC content rather than plow layer thickness of rice paddies: A county level survey from a river basin in lower Yangtze valley, China

While the impacts of farm management practices such as fertilization, tillage and straw return on soil organic carbon dynamics in croplands have been widely studied, the effects of irrigation management in irrigated rice paddies have not yet been widely assessed. Changes in plow layer thickness and soil organic carbon content of rice paddies were analyzed using data obtained in a county-level survey of soil fertility conducted in 2005 and 2006 in Guichi County, Anhui Province, China. Both soil thickness and organic carbon content of plow layer showed skewed normal distributions, with their averages of 14.58 ± 3.92 cm, and 16.45 ± 6.02 g/kg, respectively. The irrigation method was found to have significant influences on both plow layer thickness and soil organic carbon content, as the plow layer thickness and soil organic carbon content had an inverse response to the irrigation intensity derived from different irrigation methods. The land-level performance of irrigation/drainage infrastructure and the irrigation water sources were detected to have significant effect on plow layer thickness, but little influence on soil organic carbon content. While the capacity of irrigation/drainage infrastructure had a remarkable effect on soil organic carbon content but little impact on plow layer thickness. However, the irrigation condition for surveyed fields was detected to have little effect on both plow layer thickness and soil organic carbon content. These results indicated that irrigation management should keep the balance between surface erosion on plow layer thickness and soil organic carbon accumulation. Hence, developing new technique for good irrigation infrastructure and water management in future will help soil organic carbon accumulation as well as improve the soil for enhanced crop growth in rice agriculture.