Effects of different tillage systems on labile organic matter and carbon management index in purple paddy soil of long term experiment site(since 1990) were studied.Soil labile organic matter was measure by oxidation of KMnO4 with three fractionations

namely

high labile organic matter(oxidized by 33 mmol/L KMnO4)

middle labile organic matter(extra carbon oxidized by 167 mmol/L KMnO4)

and low labile organic matter(extra carbon oxidized by 333 mmol/L KMnO4).Compared with conventional tillage

long-term no-tillage and ridge culture of paddy field only can increase organic matter in surface soil(0~10 cm)

but can increase soil labile organic matter in each soil layer except in 10~20 cm;while rotation of paddy and upland would cause organic matter decrease in each soil layer

but only cause soil labile organic matter decreased in 0~10 cm soil layer.Effects of different cultivation systems on fractionation of soil labile organic matter were also studied.The results showed that no-tillage and ridge culture can increase each faction in soil surface(0~10 cm) and increase oxidative organic matter by 167~333 mmol/L KMnO4 in the other soil layers

but decrease oxidative organic matter by 33 mmol/L KMnO4

and rotation of paddy and upland also can increase oxidative organic matter by 167~333 mmol/L KMnO4 in each soil layer

but decreased oxidative organic matter by 33 mmol/L and 33~167 mmol/L KMnO4.The carbon management index was increased in each layer of no-tillage and ridge culture

while it decreased in 0~10 cm soil layer of rotation of paddy and upland.So significant influence of agricultural management and practices on soil organic matter

labile organic matter and carbon management index were found.