Effects Of Continous Super Rice Planting On Contrnt Of Organic Carbon And Aggregates Stability In Paddr Soils

The farm soil carbon pool is one of the most important carbon pools in the earth surface system. Increasing SOC levels play a critical role in agricultural sustainability and, maybe more important, inmitigating greenhouse effects and global climate changes. Aggregate is considered as a substituted index of the stability of soil structure, and the mechanisms of SOC stabilization are associated with capacity of SOC sequestration. So the studies in this field will help the governments make efficient policies to increase SOC and reduce greenhouse gas emission. And the paddy soil is very important soil carbon pools of China, which is an especial artifical wetland soil under long-term paddy management.The studied soil sampled from three sites(Chaohu in Anhui, Liuyang in Hunan, Xinghua in Jiangsu) of continuous super rice planting experiments in the mid-lower Yangtze River, in these sites, we found the testing field belonged to local super rice breeding and technic extending units, and in these field super rice was planted more than three years. We sampled soils(0-15cm) that planting super rice and not after rice harvest. Total, we sampled eight super rice planting soils and three no super rice planting soils. Undisturbed top-soil samples were separated to different size aggregates by low-energy ultra-sonic dispersion procedure. Soil aggregares, variation of SOC and SOC distribution in aggregates were analyzed to illuminate the effects on aggregates stability and SOC reserves after continuous super rice planting.This paper aimed to study:1) the change of soil organic carbon and soil active carbon(LOC, POC, MBC, DOC) after super rice pianting to illuminate difference of compose and proportion of soil organic carbon; 2) the change of aggregates distribution and stability and distribution of SOC in aggregares after super rice planting, we wanted to illuminate the organic carbon physical protecting in aggregates; 3) Effects of continuous super rice planting on the forming of big and small aggregates, and the contribution of carbon in aggregates to SOC to illuminate the longtime effect after super rice planting. The results were expected to know the effect of continuous super rice planting on soil aggregares stability and organic carbon physical protecting, which is helpful in improving carbon sink and agricultural sustainable development in paddy soil.Soil organic carbon declined(6%～14%) after super rice planting, C/N and LOC declined too, but POC, DOC and MBC increased. It had positive liner relation between the content of SOC and LOC, SOC and POC, and there was no positive liner relation between SOC and MBC, SOC and DOC.Soil samples was separated four level by low-energy ultra-sonic dispersion procedure: 2000～200μm,200～20μm,20～2μm and<2μm. Among those,2000～200μm and 200～20μm occupied the most,36.03～63.87% and 14.76～34.21% respectively. The content of 2000～200μm aggregates increased after super rice planting. The content of organic carbon in aggregates were higher in the 2000～200μm and <2μm, soil organic carbon enriched in big aggregates(2000～200μm) in our stadyed soil.The proportion of big aggregates increased after super rice planting, and the aggregates stability too. The contribution of carbon in big aggregates(2000～200μm) to soil organic carbon increased after super rice planting, the action of organic carbon physics was enhanced. Decreasing SOC was a soil dynamics after Continuous super-rice planting in short time, but did not change the carbon storage potential in long time.