Effect of different fertilization modes on topsoil organic carbon sequestration and productivity in yellow paddy field of southern China

【Objectives】 The objective of this study was to explore effects of different fertilization on topsoil organic carbon sequestration and productivity in a yellow paddy field of southern China, fix carbon and reduce carbon emission, and improve the rice yield as well. 【Methods】 Data were collected from the thirty second year of a long-term experiment in the yellow paddy field in Fujian Province. There were four fertilization treatments in the long-term field experiment: no fertilizer (CK), chemical fertilizer (NPK), chemical fertilizer plus cattle manure (NPKM) and chemical fertilizer plus straw (NPKS). We investigated influences of different fertilization regimes on topsoil organic carbon sequestration and productivity. 【Results】 Compared with the CK, the average yields of rice grain in the treatments of NPK, NPKM and NPKS were significantly increased by 67.1%, 88.1% and 84.2%, respectively, and the average yields in NPKM and NPKS were significantly higher than that in NPK. Among the fertilization treatments, the contents of top soil organic carbon were improved by 8.9%-36.8% and the content of the NPKM treatment was significantly higher than those of the NPKS and NPK treatments. Compared to the initial soil condition, the organic carbon contents in all treatments were improved by 1.84-5.26 g/kg. Taking every 10 years as the assessing period, there were significant differences of the carbon sequestration rates between the NPKM and NPKS treatments and the CK and NPK treatments, and the rates in the NPKM and NPKS treatments were 2.38 and 1.98 times of that of the CK treatment and 1.59 and 1.32 times of that of the NPK treatment during the double cropping rice years, respectively, while there was no significant difference between the NPK treatment and the CK treatment. There was a vary significant power function relationship between the annual organic carbon input and carbon sequestration in the paddy field ecosystem. The contents of fertilizing soil organic carbon were also very significantly correlated to the yields of rice grain.【Conclusions】 Compared with the single chemical fertilizer, the chemical fertilizer plus cattle manure or straw can steadily increase rice yield. The soil organic carbon will be maintained a slightly increase under the long-term no fertilizer. The soil organic carbon sequestration efficiency is gradually reduced with the increase of soil organic carbon content. Compared with the single chemical fertilizer, the chemical fertilizer plus cattle manure or straw has obvious priority in increasing the organic carbon sequestration rate, which is a win-win measure of improving the yellow paddy field productivity and fixing carbon.