Effects Of Different Organic Manures On Availability Of Soil Cadmium And Cadmium Uptake By Wheat

The heavy metal pollution in farmland soil is more and more serious,which seriously endangers the quality and safety of crops.The application of organic fertilizer can improve the soil environment,reduce the activity of soil cadmium and inhibit the absorption of cadmium by crops.In this experiment,four different organic fertilizers were used to treat the wheat field in saline alkali soil.The effects of organic fertilizer on the transformation of soil cadmium forms were discussed,and the soil physicochemical properties were determined In order to provide theoretical basis and solutions for the safe use of contaminated farmland,the inhibition mechanism of different fertilization measures on cadmium absorption of wheat was analyzed.The results show that:1.Compared with chemical fertilizer alone,increasing application of different organic fertilizers could reduce the contents of total cadmium and available cadmium in the soil to varying degrees.Among them,bio-organic fertilizer treatment had the best effect,the contents of total cadmium and available cadmium were reduced by 16.99% and67.44% respectively,compared with chemical fertilizer alone;the distribution proportion of exchangeable cadmium in each treatment of increasing application of organic fertilizer was reduced by 20%-73% compared with chemical fertilizer alone The proportion of residual cadmium in rhizosphere soil increased with the application of chemical fertilizer alone.2.The soil cation exchange capacity and p H of bio-organic fertilizer,stable manure +bio-organic fertilizer and stable manure were significantly higher than those of chemical fertilizer alone(P<0.05),which were increased by 24.92%,11.21%,18.38% and 6.24%,3.83%,2.98% respectively;the soil organic matter content of stable manure+bio-organic fertilizer was the highest,which was 25.76 g/kg;compared with chemical fertilizer alone,increasing organic fertilizer could effectively improve the soil available nutrients And the contents of total nitrogen,phosphorus and potassium in soil;3.The activities of catalase and urease in the treatment of bio organic fertilizer and manure+bio-organic fertilizer were significantly higher than those of chemical fertilizer alone(P<0.05),increased by 10.85%,8.89% and 29.07%,25.58% respectively;The activities of soil invertase and alkaline phosphatase were increased by 12-22% and 16-35%,respectively,compared with chemical fertilizer treatment;the activities of catalase and urease in the treatment of bio-organic fertilizer,manure,manure+bio-organic fertilizer were increased by 12-22% and 16-35% respectively The contents of soil microbial biomass carbon and nitrogen were significantly higher than those of chemical fertilizer(P<0.05),increased by 22.95%,11.48%,27.87% and 34.69%,14.29%,22.45% respectively.4.The grain yield and the number of grains per plant of the treatments with organic fertilizer were significantly higher than those of the treatments with chemical fertilizer(P<0.05).The number of grains per panicle and the grain yield were increased by31.87%,15.26%,30.16% and 28.91%,14.25%,23.74% respectively in the treatments of bio-organic fertilizer,farmyard manure,and farmyard manure + bio-organic fertilizer than with the treatment of chemical fertilizer alone.5.The cadmium content in wheat grain under organic fertilizer treatment was significantly lower than that under chemical fertilizer treatment(P < 0.05),and decreased by 16%～38% compared with that under chemical fertilizer treatment.The Cadmium bioconcentration factors of wheat organs under different treatments were root > leaf >stem > grain.The bioconcentration coefficient and translocation coefficient of Cd in grains of the treatments of bio-organic fertilizer,barnyard manure and barnyard manure +bio-organic fertilizer decreased by 24.55%,8.02% and 14.42% and 40.88%,18.10% and28.02%,respectively,compared with those of chemical fertilizer alone.6.The content of available cadmium in soil is mainly affected by exchangeable cadmium.Promoting the formation of organically bound cadmium can reduce the content of available cadmium,improving the physical and chemical properties of soil such as p H,alkali hydrolyzed nitrogen and biological properties such as urease and microbial biomass carbon nitrogen,which can effectively reduce the content of available cadmium in soil,thus reducing the content of cadmium that can be directly absorbed and utilized by wheat and inhibiting the absorption of cadmium by wheat Income accumulation.