Effect Of Straw Manuring On Soil Organic Carbon Fractions

High black carbon content is one of the main indicators of fertile soils. Straw can effectively increase the content of soil black carbon, and have a greater impact on soil organic carbon fractions. This paper compared three methods for the determination of black carbon content in soils in order to find a better method. With the selected method, the content of black carbon in the typical zonal soils of China was determined and the effects of straw manuring on soil organic carbon fractions were investigated.1) There are some differences for the soil black carbon content determined by the three methods. The result measured by the modified molecular marker method (BPCAs) was relatively high and the average deviation was small. The data measured by combustion method was relatively low and the average deviation is large. BPCAs stable and accurate method of measuring the low temperature (300℃,500℃) prepared biomass carbon content, biochar is more suitable for measuring low temperatures generated.2) Of20typical black carbon content of the soil redox zone determination method is2.3～37.9g/kg, with an average of16.4g/kg, coefficient of variation of68.3%, and the average percentage of organic carbon content reached85.4%far beyond the scope of the soil black carbon content, the degree of variation is much larger than BPCAs law. The average black carbon content of the soil in different regions in the order of Inner Mongolia (Duolun)> Inner Mongolia (Xilinhaote)> Heilongjiang (Hailun)> Hainan (Sanya)> Hunan (Changsha)> Zhejiang (Quzhou)> Beijing> Hubei (Wuhan).3) Straw returned and coking can improve soil aggregate content, at all levels and all the increase of the aggregate black carbon content, organic carbon content and organic carbon of soil total organic carbon ratio, especially the application of soil biomass carbon, increase the size of the larger. Different straw counters-field processing to various graded aggregate in light group and the reorganization of the impact is not big, but returning and carbonized significantly increased the weight of the light group in each graded aggregate, with the increase of biomass carbon content, soil large aggregate light group content increases, people join in the biomass carbon content and soil aggregate was significantly positively related to the quality of the light group. In addition, returning straw returned and carbonization of different graded aggregate in restructuring the molecular structure of the light group has a certain influence.