Effects Of Lanthanum On Typical Heavy Metal Accumulation And Nutrient Absorption In Black Soil And Maize Under Organic Fertilizer Application

Organic fertilizer application is an effective way to cultivate fertilizer fertility and achieve sustainable use of cultivated soil,but the residual heavy metals in organic fertilizer will accumulate in the soil and plants with application.Rare earths as micro-fertilizers can promote crop yields,improve crop quality,and regulate the accumulation of heavy metals in plants and soils.Rare earth agriculture and livestock manure can improve economic benefits,but the accumulation of heavy metals and nutrients under the application of rare earth lanthanum to organic fertilizer has not been clarified.In this experiment,the heavy metals Cu,Zn,Pb and rare earth lanthanum in organic fertilizer were taken as the research objects,and the effects of different application amounts of organic fertilizer on the accumulation of heavy metals and nutrients in black soil and maize were studied by using the method of pot experiment.The effects of lanthanum and nutrient accumulation in black soil and maize under different application rates were studied,and the effects of coapplication of organic fertilizer and rare earth lanthanum on the accumulation of heavy metals and nutrients in black soil and maize were studied,which provided a theoretical basis for further evaluation of the effect of co-application of rare earth lanthanum and organic fertilizer on the accumulation of heavy metals in black soil and maize,and the main results were summarized as follows:(1)With the increase of organic fertilizer application amount(0-13 g/kg,about 0-30 t/ha),the total and available Cu and Zn contents in black soil increased gradually.There was a positive correlation between the total Cu and Zn content in the ground and underground parts of maize and the application amount of organic fertilizer.When the amount of organic fertilizer was 13 g/kg,the total amount of Cu and Zn in black soil increased by 18.17% and 5.56% compared with CK treatment,while the total amount of Pb did not change significantly.Compared with CK treatment,the content of Cu and Zn in black soil increased by 28.37% and 42.17%.The content of available Pb in black soil decreased significantly.With the increase of organic fertilizer application amount(0-13 g/kg),the content of Cu extracted from weak acid increased from 6.24% to 7.96%,and the content of Zn extracted from weak acid increased from 2.83% to 4.69%.The content of reduced Cu in black soil increased from 16.93% to 17.98%,the content of reduced Zn in black soil increased from 18.21%to 19.20%,and the content of Cu and Zn in active soil increased.Compared with CK treatment,the total amount of Cu and Zn in above-ground part and underground part increased by 56.93%,35.53%and 39.34%,29.72%.The results indicated that heavy metals Cu and Zn accumulated in black soil and corn with the increase of organic fertilizer application rate(0-13 g/kg).Under the above conditions,the contents of total nitrogen,total phosphorus and total potassium in maize and black soil were positively correlated with the dosage of organic fertilizer.(2)Rare earth lanthanum accumulated in corn and black soil with the increase of lanthanum dosage(100-800 mg/kg).When the lanthanum dosage was 800 mg/kg,the effective lanthanum content in black soil was 23.83 times that of CK treatment,and the lanthanum content in the upper and underground parts of maize increased by 333.23% and 1280.84% compared with CK treatment.The physiological effects of rare earths are directly related to concentration,showing low promotion and high suppression.When the lanthanum dosage was 100 mg/kg,the contents of total nitrogen,total phosphorus and total potassium in maize and black soil increased significantly,and when the lanthanum dosage exceeded 500 mg/kg,the contents of total nitrogen,total phosphorus and total potassium in maize and black soil decreased significantly.(3)With the increase of lanthanum(100-800 mg/kg),the content of available Cu,Zn and Pb in black soil decreased,and the content of Cu,Zn and Pb in above-ground and underground parts of maize was negatively correlated with the amount of organic fertilizer,the accumulation coefficient of Cu,Zn and Pb in maize decreased,and the migration ability of Cu,Zn and Pb from soil to maize roots decreased.The contents of Cu,Zn and Pb in black soil decreased by 15.93%,27.58% and33.17% respectively when lanthanum was added at 800 mg/kg The contents of Cu,Zn and Pb in the aboveground part of maize were 13.87%,25.92% and 27.13% lower than that of organic fertilizer alone,the contents of Cu,Zn and Pb in the underground part of maize were 12.07%,23.34% and3.32% lower than that of organic fertilizer alone.The results showed that lanthanum inhibited the accumulation of heavy metals Cu,Zn and Pb in black soil and maize under the condition of applying organic fertilizer.In addition,the root length,plant height of maize decreased by 15.31%,8.67%,respectively,when lanthanum dosage was 800 mg/kg,compared with the treatment of organic fertilizer alone.At the same time,the contents of total N,total P and total K in maize were lower than those of organic fertilizer alone,is not conducive to the absorption and accumulation of nutrients for maize.