Effect of acidification on CEC and mineral compositions of yellow brown soils in tea gardens.

Effect of acidification on cation exchange capacity(CEC) and mineral compositions of yellow brown soils was investigated with samples of surface soils from 13-and 34-year tea gardens and a profile from 54-year tea garden.Results indicated that obvious acidification occurred in surface soils after tea cultivation of 13 and 34 years,while the contents of soil 2:1 type clay minerals and CEC did not change significantly compared with the soil from unused land.However,After tea cultivation of 54 years,further acidification occurred in surface and subsurface soils and soil pH was decreased to 3.79 and 3.70,respectively.The contents of 2:1 type clay minerals increased with the increase in soil depth and the contents of kaolinite changed oppositely.These results suggested that the extensive acidification the transformation of 2:1 type clay minerals to 1∶1 type clay mineral of kaolinite,which result in the decrease of CEC in surface and subsurface soils.