Effects of different fertilizations and cultivation years on dissolved organic carbon (DOC) in paddy soil under water-logging condition

Under water -logging condition, tempo -spatial variations of dissolved organic carbon (DOC) in Yanbian paddy soil with two cultivation years(120 years, 80 years) and three fertilization methods(chemical fertilizers, chemical and organic fertilizers, organic fertilizer) were investigated with sequential incubation method. The results showed that, there were obvious tempo-spatial variations of paddy soil DOC under water-logging condition. Chemical fertilizers or chemical and organic fertilizers were beneficial to DOC release in the upper paddy soil (0-10 cm) under water-logging condition. Organic fertilizers promoted the DOC accumulation in the lower soil (10-20 cm), and made topsoil form obvious vertical spatial heterogeneity of soil DOC. But chemical fertilizers weakened the vertical spatial heterogeneity of soil DOC. The content of DOC of the continuous cropping in 80 years was significantly higher than that of the 120 years, and the content of DOC fluctuation time of the continuous cropping in 80 years 28 dwas significantly shorter than that of the 120 years (49 d).