There is currently much interest in the dynamics of soil organic matter, which is closely related to sustainable agricultural development and global warming. The infertile red soils distributed widely in South China are important resources for agricultural exploitation in the future and can sequestrate potentially large amounts of atmospheric CO 2. \;This paper deals with the rates, process characteristics and controlling factors of the decomposition of the representative organic materials in the infertile red soils by field decomposing experiment with carborundum tube method (paddy field) or nylon bag method (upland), and its result is hoped to be the key parameters for knowledge of infertile red soil organic matter dynamics and for assessment of potential of atmospheric CO 2 sequestration.\;The experimental results shows that in the infertile red soils, the humification coefficients of organic materials were rather high, ranging from 0 28 to 0 64 with an average of 0 45. This is 9% ～ 58% with an average of 34% higher than values in corresponding red soils with normal fertility. For the organic materials there was an order of humification coefficients with green manure (0 35) > crop straw (0 40) > rice roots and wheat roots or cow feces (0 45 ～ 0 64). The effects of soil texture, soil acidity and native soil organic matter content were compared on the decomposition of rice straw and rice roots. The organic carbon of rice straw and rice roots remained after one year decomposition in the infertile red soil (clay content of 37% and derived from Tertiary red sandstone) were respectively 49% and 22.7% higher than for Quaternary red clay soil with 8 1% clay content. The organic carbon of rice straw and rice roots remained after one year decomposition in infertile red soil with 5 7 pH were 57% and 22% higher compared to those in the infertile red soil with pH of 7 2.
The native organic matter content decreased from 8 2g/kg to 3 7g/kg and 1 8g/kg would increased the organic carbon of rice straw and rice roots remained after one year decomposition by 7% and 43%. Progressive regression treatment of the data indicated that the soil acidity would be the dominant factor affecting decomposition of organic materials, and next the native soil organic matter content. Compared to those in the corresponding normal red soils, the decomposition rates of organic materials in the infertile red soils were significantly lower in the first year, but higher in the second year, thereafter no significant difference was observed between the two kinds of soils. 30kg of soil organic matter could be annually formed by the decomposition of 100kg organic materials in infertile red soils, which was also higher than those in normal red soils with corresponding value of 20kg. Accordingly, it could be suggested that because of a low decomposition rate resulting from its high clay content, acidity, and low native organic matter content, the content of organic matter in the infertile red soils could be increased quickly through proper application of organic manure.