Chemical Behavior And The Biological Effects Of Cd In Four Types Of Red Soils As Affected By Fertilizatiions

In order to reveal effect and mechanism of cultivated red soils derived from different parents and different contents of NPK Fertilizers to improve effect of Cd on growth and development of chinese cabbage. The adsorption and desorption of P and Cd in soils of Hunan Province and N mineralization based on indoor incubation treatment were investigated, to confer effects of P and Cd adsorption-desorption laws and P and Cd addition on organic N mineralization in different red soils.To control soil heavy metal pollution and provide the scientific basis to protect the vegetables security, the pot tests have been done on cultivated red soils about the growth and development of Chinese cabbage of different concentrations of heavy metals cadmium (0,0.5,1mg·kg-1),N (0.10,0.15,0.30g·kg-1),P(0.10,0.30g·kg-1),K(0.15g·kg-1)and single and combined pollution. The main results were as below:(1) Amount of Cd adsorbed of limestone red soil was biggest in four red soils,amount of Cd adsorbed of quaternary red soil was least. In red slate soil and granite red soil the adsorption character of Cd were similar.Compare with CK, amount of Cd desorption of the other treatment all increased in red soils treated with different concentration of P addition, except CdlO treatment of quaternary red soil and red slate soil, which to show that P addition promoted contents of Cd desorption. amount of Cd desorption of the other treatment all increased as amount of Cd adsorption increased, in addition to red slate soil and limestone red soil(except Cdl treatment), the law of desorption of Cd was in concert with desorption rate of Cd. The amount of Cd desorption in granite red soil increased as amount of Cd adsorption increased, in the meantime, desorption rate of Cd increased as amount of Cd adsorption increased prior to Cd10treatment. Amount of Cd desorption of the other treatment increased as amount of P adsorption increased, amount of Cd desorption of the Cd0.5and CdlO treatments first increased and then decreased as amount of P adsorption increased.The maximum of Cd desorption accounted only30.14%for quantity of adsorption.Amount of P adsorbed all increased as amount of P addition increased in Cd adsorbed of four red soils, even, amount of P adsorbed of quaternary red soil was maximum, the second of red slate soil. In limestone red soil and granite red soil the adsorption character of P were similar.Compare with treatment without Cd addition, the amount of secondary adsorption of P of the treatment with Cd decreased in four red soils.On the whole,amount of P adsorption decreased as amount of Cd adsorption increased. Amount of P adsorption increased as amount of P adsorption increased. Minimum value of amount of P adsorption appeared in different quantity of Cd adsorption of different red soils, which maybe related with soil physicochemical properties.(2)N mineralization average accumulation in the other red soils except quaternary red soil increased first and then decreased as the P addition, and the largest amount of N mineralization in the0.1g·kg-1P addition,increased with increase of P addition amount treated with P concentration of0-0.5g·kg-1range.N mineralization was inhibited by Cd in both quaternary red soil and limestone red soil treated with Cd concentration of0-1.0mg·kg-1range,and the largest decline of N mineralization were4.98mg·kg-1and6.53mg·kg-1. P-Cd interactive processing promoted N mineralization accumulation in the other red soils except quaternary red soil,moreover,N mineralization accumulation were difference in different parents of soils. The strongest promotion of organic N mineralization in the red soils polluted by mild Cd was treated with0.3g·kg-1and0.5g·kg-1P.(3) The Cd content of chinese cabbage all decreased in the other treatment except for Cd1.0N0.1P0.1treatment in quaternary red soil,compared with the control. High P treatment treated effect more than low P about reducing the pollution of cadmium. The application of a high rate of phosphate fertilizer coupled with mid high rates of nitrogen and potassium fertilizers led to lowest Cd content of chinese cabbage and optimum yield. Low Cd treatment in two red soils the optmiun combination of the three fertilizers is N0.1g·kg-1.P0.3g·kg-1,K0.15g·kg-1High Cd treatment in granite red soil the optmiun combination of the three fertilizers is N0.15g·kg-1,P0.3g·kg-1,K0.15g·kg-1,which gave the crop a yield,amounting to89%of the actual highest yield,and Cd content,ranging lowest.(4) The application of middle rate of N and P fertilizer coupled with mid-high rate of K fertilizers led to optimum yield and lower Cd cumulative content of Chinese cabbage in red slate soil.Regression and frequency analysis revealed that the optmiun combination of the three fertilizers is N g·kg-1+P0.32g·kg-1+K0.15-0.20g·kg-1,which gave the crop a yield,amounting to90%-100%of the actual highest yield(42.03g/pot),and a low Cd cumulative content, tranging between0-0.74ug/pot.The application of mid-low rate of N and K fertilizer coupled with mid high rate of P fertilizers led to optimum yield and lower Cd cumulative content of Chinese cabbage in limestone red soil.Regression and frequency analysis revealed that the optmiun combination of the three fertilizers is N0.08-0.10g· kg-1+P0.25-0.35g· kg-1+K0.08-0.10g· kg-1,which gave the crop a yield,amounting to90%-100%of the actual highest yield(134.84g/pot),and a low Cd cumulative conten,trang ing between0-0.74ug/pot.