Passivation Of Copper And Zinc In Swine Manure Organic Fertilizer

By adding vermicompost(VER),biochar(BC)and phosphorus modified biochar(PBC)to swine manure organic fertilizer contaminated with Cu and Zn under different pH conditions,study the effects of passivators on the morphology of Cu and Zn in fertilizer,explore the influences of the addition amount and fertilizer pH on the passivation effect,and evaluate the effects of three passivators on fertilizer performance.X-ray fluorescence spectrometry(EDX)and scanning electron microscopy(SEM)were used to determine the composition and surface morphology of the passivators,and the pH value and nutrient content of the passivators were measured.Experimental results show that all the passivators showed the best passivation effect at pH 6.55.The passivation effects of VER,BC and PBC on acid extractable state Cu in organic fertilizers were 30%,24%,19%,the passivation effects on acid extractable state Zn in organic fertilizers were 42%,8.6%,9.4%.VER has the best passivation effect on Cu and Zn in organic fertilizer when the dosage was 40.The passivation amounts were 0.09mg/kg and 2.52 mg/kg respectively,and the passivation rates were 37%and 43%;BC has the best passivation effect on Cu when the dosage was 10,the passivation amount was 0.043 mg/kg,and the passivation rate was 23%.And the passivation effect of BC on Zn is the best when the dosage was 40,the passivation amount was 1.36 mg/kg,and the passivation rate was 21%;The passivation effect of PBC on Cu is the best when the dosage of PBC is 30,the passivation amount was 0.033 mg/kg and the passivation rate is 21%.The passivation effect of PBC on Zn is the best when the dosage is 40.The passivation amount is 2.058 mg/kg and the passivation rate is 33%.The results of plant experiments showed that the change trends of the contents of Cu and Zn in plants and that of acid extraction state Cu,Zn in fertilizers are basically the same.The content of Zn in cabbage reaches the minimum when the passivator dosage was 40,where Zn content is 40-BC>40-PBC>40-VER,the content of Cu in cabbage is 30-PBC>10-BC>40-VER.The results show that phosphorus-modified biochar can enhance the passivation ability of biochar to Zn.From the effect of adding passivators on fertilizer traits,adding BC and PBC can effectively improve the agglomeration of fertilizers.Under the dosage of three passivators used in the experiment,it can be basically ensured that the organic matter and total nutrient content of organic fertilizer can meet the standards.And also the fresh weight,dry weight and height of plant of cabbage can be increased by varying degrees.The improve efficiency of three passivators is as follows:BC>PBC>VER.When the dosage of BC was 40,the organic matter content and total nutrient content of fertilizer are both the highest,reaching 47.91%and 9.37%separately.The fresh weight,dry weight and height of plant of cabbage increased by 85%,55%and 19.1%compared with those without passivator.The experimental results show that the effect of VER as a passivator for metal Cu and Zn in organic fertilizer is better than BC and PBC.But the content of organic matter and total nutrients decreases,the growth of plants which apply fertilizers added VER is not good.Therefore,when VER was used as a passivator for Cu and Zn in organic fertilizers,it is necessary to supplement nutrients.