Stability and It's Mechanism of Aggregates in Easily Eroded Soils Derived from Purple Rock in the South of Zhejiang Province

WANG Hong-yan 1,WU Shi-wen 2,MA Hai-yang 2,Guo Junling 1,LU Sheng-gao 1(1.College of Environmental and Resource Sciences,Zhejiang University,Hangzhou 310029,China;2.College of Resource and Environmental Sciences,Henan Agricultural University,Zhengzhou 450053,China)

Purple rock;Aggregate stability;Wet-sieving method;Le Bissonnais method

Soil aggregate stability is a crucial index affecting soil quality and erodibility.Aggregate stability of orange garden soils derived from purple rock was measured by applying wetting sieving method and Le Bissonnais method,and the relationship between aggregate stability and soil cementing matter(organic carbon,clay and free Fe oxides content) was also assessed.Results indicated that aggregate stability varied greatly among soils.The mean weight diameter(MWD) ranged from 0.75 mm to 3.49 mm and MWDdry-wet values from 0.15 mm to 2.89 mm.The mean MWDs for three treatments developed by Le Bissonnais ranged from 1.57 mm to 3.12 mm.There were highly significant correlation between MWD values of three treatments developed by Le Bissonnais and >0.25 mm water-stable aggregate content,MWD and percentage aggregate disruption determined by wet-sieving method,suggesting that aggregate stability defined by Le Bissonnais method is well comparable with the routine Yoder method.The MWD of three treatments(fast wetting,slow wetting and stirring after pre-wetting) measured on 5-2 mm aggregate had the following order:FWmicro-cracking>mechanical breakdown.The aggregate stability was significantly correlated with clay and free iron oxide contents.However,soil organic matter mainly affected the amount of water-stable aggregate in soils,which highly related to the MWD.