The Effects Of Soil Cd Pollution And Agronomic Regulating Techniques On The Cd Accomulation Of Apple Tree

10-year-old pot Fuji apple trees were used as materials to study the effects of soil Cd pollution by adding different dose Cd Chloride solution to soil on the photosynthesis, the fruit quality of apple, and the soil Cd content change regulate in different forms(E.X., B.C.,B.O.M.,B.I.M.,Re.),and the regulating effects of adding 3 kinds of improver(KH2PO4,Bio-organic fertilizer,CaO)to the Cd polluted soil were also studied.The results showed that:1. In different growth periods of apple trees, the soil Cd contents in different forms(E.X., B.C., B.I.M., B.O.M., Re.) were as follows: high-dose (40 mg·kg^-1)> moderate-dose (20 mg·kg^-1)> low-dose (5 mg·kg^-1) treatments, and there existed significant or very significant positive correlation among the soil Cd contents in different forms and soil Cd contents. The Cd contents in different forms were: E.X.>B.I.M>Re.>B.C.>B.O.M. In different growth times, the soil Cd content in different forms reduced in power index, the Re. Cd content increased in index.2. The Cd contents in different growth periods were: Full-bloom stage(Apr-23rd) > physiological fruit drop stage(Jun-23rd) > Fruit swelling stage(Aug-23rd) > Fruit mature stage(Oct-23rd). The Cd decrements treated in the soil of 0-80,0-60,0-40 cm layer from full-bloom stage to physiological fruit drop stage were the largest; and that of treated in the soil of 0-20 cm layer from physiological drop stage to Fruit swelling stage were the largest.3.There existed significant or very significant positive correlation(P>0.7117) between the soil Cd content and the leaf Cd content in different growth period. Leaf Cd content increased by the time of soil treatment witn Cd going on, and it reached the peak value at the period of fruit slow growing period(23th,Sep), and then declined; The higher of the soil Cd content, the larger of the fruit Cd content. There was a very significant positive correlation(P>0.9834) between the fruit Cd content and soil in mature period, and the fitting equation is: y=0.0248x^0.2001.According to the pollution free apple fruit whose Cd content was lower than 0.03 mg·kg^-1, The maximal soil Cd content calculated by the formula in brown soil(pH 7.133)was 2.59 mg·kg^-1.so as to produce pollution free apple.4. Under different dose soil Cd treatments, the contents of Chlorophyll a, chlorophyll b, total chlorophyll,Pn.,Tr. and Gs.were as follows:CK (0 mg·kg^-1)>low-dose (5 mg·kg^-1)> moderate-dose (20 mg·kg^-1)>high-dose (40 mg·kg^-1).There existed very significantly negative correlations among the contents of Chlorophyll a, chlorophyll b, total chlorophyll,Pn.,Tr.,Gs.and the soil Cd content; Single fruit weight, fruit hardness, fruit transverse diameter and vertical diameter, fruit shape index, the contents of total sugar, glucose, fructose, reducing sugar and soluble solid were as follows:CK (0 mg·kg^-1)>low-dose (5 mg·kg^-1)> moderate-dose (20 mg·kg^-1)>high-dose (40 mg·kg^-1).There were significant or very significant negative correlations among single fruit weight, fruit hardness, fruit transverse diameter and vertical diameter, fruit shape index, total sugar, glucose, fructose, reducing sugar, soluble solid and soil Cd content; There were no significantly correlation between fruit titraTablele acid and soil Cd content.5. The soil E.X Cd content, leaf and fruit Cd contents treated by adding 3 kinds of improver to to the Cd polluted were lower than that of CK(CK added Cd solution only), the reduced amounts were 9.9 %～36.6 %,3.1 %～41.6 %,0.5 %～53.9 % respectively; The soil B.C., B.I.M., B.O.M., Re. Cd contents were higher than that of control, and the increased amounts were 6.2 %～61.2 %,0 %～91.7%, 0 %～314.7 %,0 %～57.9 % respectively. Among the agronomic regulating techniques to reduce the harm of Cd pollution, the treatments of 0.5 g·kg^-1KH₂PO₄ + 200 g·kg^-1 Bio-organic fertilizer + 40 g·kg^-1CaO and the treatment of 1 g·kg^-1KH₂PO₄ + 200 g·kg^-1Bio-organic fertilizer + 20 g·kg^-1CaO were the best. According to the fruit and soil Cd content to fitting curve, which figure out the treatment 0.5 g·kg^-1KH₂PO₄+200 g·kg^-1 Bio-organic fertilizer +40 g·kg^-1CaO was the best when the soil Cd content was lower than 2.95 mg·kg^-1, and the the treatment of 1 g·kg^-1KH₂PO₄ + 200 g·kg^-1Bio-organic fertilizer + 20 g·kg^-1CaO was the best when the soil Cd content was higher than 2.95 mg·kg^-1 .The limit soil Cd content was lower than 11.59 mg·kg^-1 which could be regulated by agronomic regulating techniques .The effects of CaO on reducing the E.X., Re. Cd content, leaf and fruit Cd contents were the best among the 3 kinds of soil improver, the direct path coefficients were -0.4494～-0.7924, 0.8581～0.9445, -0.6671～-0.7652, -0.7832～-0.9027 respectively; KH₂PO₄ on reducing the B.C., B.I.M contents were the best, the direct path coefficients were 0.8097～0.9079, 0.8527～0.9327; Bio-organic fertilizer on reducing B.O.M Cd content was the best, the direct path coefficient was 0.7663～0.8903.6. The regression equations showed that: there existed significant or very significant correlation among soil Ex., B.C., B.I.M, B.O.M Cd contents and leaf, fruit Cd contents. There existed negative correlation among soil B.C., B.I.M, B.O.M. Cd contents and leaf, fruit Cd contents. The higher the B.C., B.I.M., B.O.M. Cd contents, the lower the biological effectiveness of soil Cd.