| According to the Environmental quality standard for soils (GB15618-1995)of secondary standard(dryland), zinc and chromium(ZnCl2,CrCl6.6H2O) were put in the test purple soil from Sichuan Agricultural University farm, and then two amendments of lime and superphosphate were added. Through the pot experiment by means of monoculture (corn, soybean and cowpea) and intercropping(corn‖soybean and corn‖cowpea), it comprehensively studied the zinc and chromium effectiveness, nutrient availability and the change of soil pH in rhizosphere and non-rhizosphere soil, the zinc and chromium accumulation, nutrient (nitrogen, phosphorus and potassium) absorption and biomass et al in crops under the interactions of the two amendments and planting patterns. Based on these, compared with the restoration effects of different amendments, crop species and planting patterns on zinc and chromium contaminated soil, it provided a theoretical basis of crop safety production in zinc and chromium contaminated soil. The major findings were as follows:1.For the soil available zinc and chromium, the contents showed rhizosphere soil> non-rhizosphere soil. Under the same planting pattern (monoculture or intercropping), the contents of available zinc and chromium in soil treated by different amendments, which reached the minimum both at lime(high concentration) and superphosphate(low concentration respectively), were fewer than the CK, and the contents order:CK> lime (low concentration)> lime (high concentration), CK>superphosphate (high concentration)> superphosphate (low concentration); it indicated that maintaining high soil pH was more effective on the reduction of soil zinc and chromium availability. Under the different planting patterns, the contents of available zinc and chromium in soil treated by the same concentrations of amendment distributed:monoculture> intercropping. It indicated that intercropping was more beneficial than monoculture in the reduction of availabilty of zinc and chromium in the soil by the amnedments,and further the accumulation in the crop.2.The two amendments significantly inhibited the absorption of zinc and chromium in soil, and with better effects of the lime than the superphosphate. Under the same planting pattern and different concentrations of amendments, in spite of monoculture or intercropping, the contents of zinc and chromium in roots, stems and leaves distributed: CK> lime (low concentration)> lime (high concentration), CK> superphosphate (high concentration)> superphosphate (low concentration). This performance was similar to soil zinc and chromium availability, indicating the absorption of zinc and chromium in crop have a positive correlation with the zinc and chromium availability in soil. Those in roots, stems and leaves of corn, soybean and cowpea treated by the different planting patterns and same concentrations of amendments showed:monoculture> intercropping, which indicated that intercropping played a more important role in reducing the accumulation of zinc and chromium in plant bodies.3.The contents of hydrolyzable nitroge, available phosphorus and available potassium showed:rhizosphere soil> non-rhizosphere soil after addtion of amendments, and the availability of soil nutrients was significantly improved. At the same time, the amendments had significantly increased the absorption of soil nutrients (nitrogen, phosphorus and potassium)of crops, and those of nitrogen, total phosphorus and total potassium in plant bodies improved compared with the CK, and the improvement by superphosphate was better than lime. Under the different planting patterns and same concentrations of amendments, the contents of total phosphorus and total potassium in roots, stems and leaves of corn, soybean and cowpea showed:intercropping> monoculture, with obvious intercropping advantages. And the total nitrogen in corn showed:intercropping> monoculture, but the total nitrogen in soybean and cowpea showed monoculture> intercropping.4. The amendments promoted crops growth, and the biomasses order:superphosphate > lime. Under the same concentrations of amendments, the biomasses of corn intercropping were more than corn monoculture, but the biomasses of soybean (cowpea) intercropping were fewer than those of monoculture. It indicated cron intercropping was more significant in general, soybean and cowpea were not.5. The amendments effectively reduced the transformation of zinc and chromium in aerial parts and seeds. The contents of zinc and chromium in corn, soybean and cowpea seeds showed:lime> superphosphate, monoculture> intercropping. According to the Food Hygiene Standard, the contents of chromium in soybean and cowpea seeds in this experiment were lower than those in the standard; while, the contents of zinc in soybean and cowpea seeds met the standards. In addition, by the treatments of superphosphate, the contents of zinc in monoculture and intercropping corn seeds reached the standard, and some of lime treatments reached the standard as well.6. The general changing trend of soil pH showed:rhizosphere soil superphosphate. Under the same planting patterns, the order of soil pH treated by different concentrations of amendments was:lime (high concentration)>lime (low)> concentration, CK> superphosphate (low concentration)>superphosphate (high concentration). For the different planting patterns, the pH values of rhizosphere and non-rhizosphere soil of corn/soybean and corn/cowpea treated by lime were between those of the corn monoculture and soybean (cowpea) monoculture, and those treated by superphosphate showed:intercropping> monoculture.The results above indicated that, the effectiveness of zinc and chromium significantly declined through lime and superphosphate application on the pH in zinc and chromium contaminated soil.So the accumulation of zinc and chromium was reduced in corn, soybean and cowpea, and the migration and transportation capacity of zinc and chromium slowed down. For the restoration effects of amendments, the lime(high concentration) had the best effects while the superphosphate(high concentration) had the fewer effects; and for planting patterns, the intercropping was better than monoculture. Meanwhile, the amendments had significantly increased the absorption of soil nutrients (nitrogen, phosphorus and potassium), and then increased the soil nutrients absorption of plants, which promoted crops growth and production. For the comparsion of the two amendments, the improvement showed:superphosphate> lime. For the comparsion of the different planting patterns, the effect of intercropping was better than monoculture effect. Therefore, amendments and crop intercropping could be recommended for the restoration of zinc and chromium contanminated soil.
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