Abstract:Soluble organic nutrients in soil, including soluble organic nitrogen (SON) and carbon (SOC), play an important role in the biogeochemistry of carbon, nitrogen, and phosphorus, in pedogenesis, in the transport of pollutants, and in long-term carbon storage. Many Chinese soils have received long-term applications of organic fertilizers. Organic fertilizers, like manure, contain soluble inorganic and organic nutrients. Both types of nutrients are very active in soil. Little is known about the content and characteristics of SON and SOC in the manures used in China. A laboratory experiment was conducted to measure the concentration of SON and SOC extracted with water and 0.01 mol/L CaCl2 from different types of organic manure. Additional characteristics were also evaluated. Results showed that the average concentration of water extractable SON in the seven manures was 105.2 mg/L. The average concentration of CaCl2 extractable SON was 91.6 mg/L. SON in the manures accounted for 70% of the total soluble nitrogen (TSN) and 5% of the total nitrogen (TN). On a dry weight basis, the average content of water extractable SON was 1188 mg and average CaCl2 extractable SON was 1037 mg/kg. The average concentration of water extractable SOC in the seven manure types was 695 mg/L. CaCl2 extractable SOC averaged 622 mg/L. SOC accounted for 2% of the total organic carbon (TOC) in the manure. On a dry weight basis, the average content of water extractable SON in the manure was 7873 mg/kg. CaCl2 extractable SON averaged 7054 mg/kg. The ratio of SOC/SON in the manures was about 6.8. There was a significant correlation between SON and SOC (P<0.05) in the manure. A negative correlation was observed between the concentration of SON and NO-3-N (P<0.05). The results indicate that SON and SOC are important constituents in organic manure. More attention should be paid to these constituents in order to reduce nitrogen and carbon loss from manure fertilizer to the environment.