Development And Preliminary Application Of A Cow Manure Organic Fertilizer Product With Low Heavy Metal Availability

China's intensive and large-scale aquaculture industry produces a large amount of livestock and poultry manure every year.The production of organic fertilizer by composting and application to farmland is the main way to solve the pollution of livestock ma nure.In this process of resource utilization,the unreasonable application of organic fertilizers in livestock and poultry will cause pollution to the soil environment.In view of the problem that the application of organic manure in livestock manure may lead to the accumulation of heavy metals in the soil,this paper mainly discusses the effect of traditional livestock and manure application on the availability of typical heavy metals in the soil.Based on this,a new type of organic fertilizer product with low heavy metal effectiveness is developed.Finally,the application effect of the above new organic fertilizer products was investigated.The main findings are as follows:(1)Using corn as a trial crop,pot experiment was conducted to investigate the accumulation of typical heavy metals in soil and maize plants and the growth of corn under the conditions of application of traditional cow manure organic fertilizer in two soils with different physical and chemical properties.Soil nutrient regulation.Th e results showed that the application of cow manure organic fertilizer could significantly increase the p H value,organic matter,total nitrogen,total phosphorus and available phosphorus content of the two soils;the total nitrogen content of maize plants did not change significantly,and the total phosphorus content increased significantly.With the increase of fertilization amount of cow manure organic fertilizer(15-60 g/kg),the effective lead(DTPA-extracted state)content in the two soils increased by 9.63%,which was effective compared with the control without application of cow manure organic fertilizer.Cadmium(DTPA-extracted state)increased by up to 10.28%.There was a significant difference in lead content in corn plants under different dosages of cow manure organic fertilizer,with the highest increase of 1.60 mg/kg;the highest cadmium content in corn plants increased by 0.04 mg/kg,but there was no significant d ifference between the dosages.(2)The test uses biochar(BC),nano zero-valent iron(n ZVI)and cow manure organic fertilizer as test materials.By adjusting the ratio of the three materials,it is effective to check the heavy metals in cow manure organic fertilizer under different ratios.A new organic fertilizer product with a low content of low-weight metals.The results showed that the addition of BC and n ZVI could significantly reduce the available content of heavy metals in cow manure organic fertilizer.The ratio of BC:n ZVI=1:3(mass ratio)is the best for the passivation of heav y metals in cow manure organic fertilizer.Under the above ratio,the passivation of typical heavy metals(lead and cadmium)in cow manure organic fertilizer is increased with the addition of BC and n ZVI(5%,10%,15%,20%,mass ratio).The efficiency grad ually increased,and the content of available lead and available cadmium in cow manure organic fertilizer decreased by 56.55% and 42.47%.Combined with the principle of economy,the ratio of new organic fertilizers for subsequent research was determined as follows: BC: n ZVI = 1:3,and the ratio of addition of BC and n ZVI was 10%.Under the above conditions,compared with traditional cow manure compost,the content of available lead and available cadmium decreased by 24.24% and 24.45%.(3)Using corn as a trial crop,using pot experiment to investigate the accumulation of typical heavy metals in soil and maize plants under different application conditions of organic manure(traditional cow manure organic fertilizer,new organic fertilizer)and corn growth and soil.Nutrient changes.The results showed that both organic fertilizers could increase the p H value,organic matter,total nitrogen,total phosphorus content and total nitrogen and total phosphorus content in maize plants,and there was no significant di fference between the two organic fertilizer treatments.Under the conditions of different dosages,there was a significant difference in soil heavy metal content between the two organic fertilizer treatments.Under the condition of new organic fertilizer treatment,the effective lead content in soil was up to 23.83% lower than that of traditional cow manure organic fertilizer treatment,and the effective cadmium content was decreased by 13.23%.It shows that the heavy metals in the soil are more stable under the condition of applying new organic fertilizer compared with traditional organic fertilizer.Under the conditions of different dosages,there was a significant difference in the content of heavy metals in corn plants between the two organic fertilizer treatments.Under the condition of new organic fertilizer treatment,the lead content in the aboveground and underground parts of maize plants was 6.58% and 21.45% lower than that of traditional cow manure organic fertilizer treatment,and the cadmium content decreased by 27.48% and 14.73%,respectively.It shows that compared with traditional organic fertilizer,the application of new organic fertilizer can inhibit the absorption of heavy metals by plants.