Efects of cropping system of the rotation of upland crop and rice on the total and available copper contents in soils

The study on the effects of cropping system transformation from upland farming to the rotation of upland crop and rice on the total and available copper contents in calcic concretion black soils shows that the EX-Cu is the intensity factor of the available copper；the OM-Cu，AFeO-Cu，MnO-Cu and Carb-Cu are the capacity factor of the available copper；the Res-Cu and CFeO-Cu are unavailable for plants but can be activated under the artificial cultivation．The ratios of Res-Cu，CFeO-Cu，Carb-Cu and MnO-Cu to the total copper during the rotation of upland crop and rice decrease and on the contrary，thoseof OM-Cu，Ex-Cu and AFeO-Cu increase，which enablethe copper to be moremovableand available，and finally lead to the reduction of total copper contents in tilling layer due to leaching．