Abstract: In this paper,the distribution and forms of Fe and Mn in rhizosphere soils planted with five varieties of crops were investigated by using the rhizobag system.The results show that exchangeable Fe(EX-Fe),carbonate-bound-Fe(CARB-Fe),amorphous Fe oxides(AO-Fe)and exchangeable Mn(EX-Mn),carbonate-bound-Mn(CARB-Mn)are accumulated significantly in rhizosphere soils.The amount of which are different among the rkizosphere soils of five crops.Correlation analysis shows that both the Fe content in the plants and the amount of Fe absorbed by plants are positively correlated with AO-Fe content in rhizosphere of yellow fluvo-aquic soil.Besides the influence of PH change in rhizosphere, the mobilization of insoluble Fe-by root exudates may be related to the accumulation of available Fe in rhizosphere.The accumulation of available Mn in rhizosphere is associated with rhizosphere Eh.

Key words: Rhizosphere Calcareous soil, Distribution and forms of iron and manganese, Taihu Lake basin., landscape ecological risk, CLUE-S model, shift of gravity center