Efects of cropping system of the rotation of upland crop and rice on the total and available copper contents in soils
旱改水对土壤铜含量及其有效性的影响研

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, those of OM Cu, Ex Cu and AFeO Cu increase, which enable the copper to be more movable and available, and finally lead to the reduction of total copper contents in tilling layer due to leaching.