By using a combination of multiple soil fractionation methods which does not destroy the basic structure of organic carbon physics group

a five consecutive years experiment was conducted to evaluate the effects of various types of organic materials

such as milk vetch

rice straw and organic poultry manure on soil organic carbon and its physical componets in paddy fields. The results shows that

soil aggregate was mainly distribution in the grade 2～0.25 mm and 0.25～0.053 mm

and the aggregate particle organic carbon concentration decreased with the decrease of particle size. The organic carbon storage in the 0.25～0.053 mm and ＜0.053 mm particle size aggregates increased by using different organic materials

and the treatment with milk vetch

straw and organic fertilizer all increased the amount of soil organic carbon. The results indicate that the organic material returning to the paddy soil can greatly increase the carbon storage in the soil micro aggregates. Returning organic material to the paddy soil increased the concentration oflight fraction particles and reduced the concentration of the heavy fraction particles in soil. Organic materials application in the paddy soil is helpful for the formation of light fraction particles in soil. Among the different physical fractions in soil used for rice cultivation

light fraction organic carbon correlated significantly with ＞0.25 mm aggregate organic carbon and ＜0.053 mm aggregate organic carbon and highly significantly with aggregate organic carbon in the 2～0.25 mm size fraction. Returning organic material in the paddy soil can promote the formation and development of soil aggregates and the fixation of organic carbon

effectively improve the soil micro aggregates and light fraction content

and increase the soil carbon storage in micro aggregates and light fraction organic carbon reserves

change the composition characteristics of organic carbon in paddy soil.