Effects Of Different Nitrogen,Phosphorus,and Potassium Fertilizers On Uptake Of Cd And Zn In Sedum Plumbizincicola Intercropped With Wheat

In order to study the effect of agricultural fertilization technical measures on the efficiency of bioremediation of contaminated farmland soil,under the condition of Sedum plumbizincicola intercropping wheat（Jima 22）,pot experiments were used to study the effects of different nitrogen fertilizers and inhibitors,different phosphorus and potassium fertilizers and dosages on the p H and available Cd and Zn contents of contaminated soil,growth and Cd,Zn uptake,and removal rate of Sedum plumbizincicola and wheat.The main changes in Zn content are as follows:Compared with the corresponding treatment without fertilization,urea and ammonium sulfate,calcium superphosphate,potassium chloride,and potassium sulfate all reduced the soil p H by 0.08～0.44 units,while nitrogen fertilizer sodium nitrate and phosphate fertilizer calcium magnesium phosphate increased soil p H by about 0.11～0.32 units.Nitrogen fertilizer added DCD and NBPT delayed the time when soil p H started to drop,but only DCD added to make p H drop at 30d,while adding DCD and NBPT at the same time started to drop 15d later.Compared with sodium nitrate,urea and ammonium sulfate increased soil available Cd content by 91.8%～96.4%,and available Zn content by 90.6%～104.2%.Calcium magnesium phosphorus fertilizer reduced the available Cd and Zn content compared with no phosphate treatment,and calcium superphosphate increased the available Cd and Zn content,which were90.9%～115.9%and 42.5%～66.5%higher than the high calcium magnesium phosphate fertilizer,respectively.Compared with no potassium fertilizer application,the application of potassium chloride and potassium sulfate both increased the effective Cd and Zn content,increased the available Cd content by 11.5%to 52.1%,and the available Zn content reached5.9%to 33.9%,of which high Potassium chloride increased the available Cd content significantly higher than the high amount of potassium sulfate,up to 18.4%.Both urea and ammonium sulfate increased the uptake of Sedum plumbizincicola compared to sodium nitrate,and the urea treatment（UDN）added with DCD and NBPT had the highest Cd and Zn uptake,their Cd uptake was respectively higher than only adding DCD ammonium sulfate（SD）and only adding DCD urea（UD）treatment were 11.86%and 7.25%higher,and Zn uptake was 8.05%and 5.49%higher,respectively.There was no significant difference in the uptake of Cd and Zn between medium and low amounts of superphosphate and calcium magnesium and phosphate fertilizers in Sedum plumbizincicola,and the highest uptake of Cd and Zn was observed in high-level superphosphate treatment,which were higher than the high amounts Calcium magnesium phosphate treatment 9.5%and 20.3%.Compared with the treatment without potassium fertilizer,the medium and high amount of potassium chloride and potassium sulfate both increased the Cd uptake of Sedum plumbizincicola by40.2%～73.3%and Zn uptake by 15.1%～27.0%.The uptake of Cd and Zn in wheat treated with urea and ammonium sulfate increased significantly compared with sodium nitrate,reaching 22.5%～79.4%and 39.5%～97.4%,respectively.Although the uptake of Cd and Zn in wheat treated with UDN was significantly higher than that in the treatment without nitrogen fertilizer,the concentration of Cd was significantly lower than that in the treatment without nitrogen fertilizer by 10.1%.The Cd and Zn uptake of wheat treated with different application rates of superphosphate and calcium magnesium phosphate fertilizers were not significantly different from those of non-phosphate fertilizer treatments.The uptake of Cd and Zn in wheat treated with high potassium chloride and potassium sulfate increased significantly compared with the treatment without potassium fertilizer.The uptake of Cd increased by 41.5%and 36.3%,and the uptake of Zn increased by48.8%and 44.2%,respectively.Compared with sodium nitrate and non-nitrogen fertilizer,both urea and ammonium sulfate significantly improved the removal rate of soil Cd and Zn,and the highest rates of UDN treatment were 27.93%and 7.36%,respectively.There was no significant difference in the removal rates of Cd between high,medium and low amounts of superphosphate and calcium magnesium phosphate fertilizers.However,compared with high calcium magnesium phosphate fertilizers,the removal rate of high calcium superphosphate Zn was significantly higher by77.7%.There was no significant difference in the removal rates of Cd and Zn between low and medium doses of potassium chloride and potassium sulfate,but compared with high amounts of potassium sulfate,the removal rates of Cd and Zn were the highest in potassium chloride treatment,and were 40.5%and 52.6%higher,respectively,of which there is no significant difference between high potassium chloride and medium potassium chloride.Under the condition of intercropping Sedum plumbizincicola and wheat,the application of DCD and NBPT urea(300 mg kg^-1),high amount of calcium superphosphate(200 mg kg^-1)and medium amount of potassium chloride(100 mg kg^-1)on the soil of contaminated farmland,can not only increase the effective content of cadmium and zinc in soil,the absorption of cadmium and zinc in Sedum plumbizincicola and its repair efficiency,but also effectively prevent the significant increase in cadmium and zinc absorption in wheat.It is the best fertilization technology under the cropping pattern of cadmium and zinc contaminated farmland with Sedum plumbizincicola and wheat intercropping.