Study On The Characteristics Of Ectopic Fermentation Of Pig Manure And Environmental Risk Assessment Of Its Product

The ectopic fermentation technology of using microbial metabolic activities to compost agricultural wastes with livestock manure and produce organic fertilizers is one of the main modes of manure treatment of livestock breeding in China.In view of the problems of low litter selection,high cost and nutrient loss in the composting process in actual production.In this paper,combined with the local situation in Chongqing,the traditional sawdust and bran shell litter were partially replaced by oil olive pomace,and microorganisms with nitrogen fixation,phosphorus and potassium were used to construct fermentation fungi,and aerobic composting experiments were carried out with pig manure in farms,and the changes of basic parameters,nutrient content and maturity indexes in the composting process of different treatment groups were compared and studied,and heavy metal and antibiotic residues before and after composting were determined by inductively coupled plasma mass spectrometry and high performance liquid chromatography.The changes and functions of bacterial communities during composting were studied by high-throughput sequencing technology.The improvement effect of well-rotted fertilizer on potted soil was verified from the aspects of soil fertility,soil enzyme activity and microbial number,and the heavy metal content of soil was determined by inductively coupled plasma mass spectrometry,and the risk of heavy metals after the application of rotted manure into soil was discussed.This study provides a scientific basis for ectopic fermentation of pig manure and resource utilization of agricultural waste.1.The addition of olive pomace and nitrogen-fixing phosphorolytic potassium bacteria could increase the ectopic fermentation temperature and high temperature maintenance time,among which olive pomace accounted for 25%,and the treatment with functional fungi(B3 group)performed best,the highest temperature reached 63.2 °C;the p H of each group showed an increasing trend,while the EC value first increased and then decreased,and the moisture content remained at about 50%.The seed germination index(GI),fecal coliform number and roundworm egg mortality in each treatment group all reached the national organic fertilizer safety standards,and the B3 group had the highest GI at the 20 th day,reaching 113%.The contents of heavy metal elements arsenic,cadmium,chromium,mercury,lead and nickel showed a gradual increase in the composting process,and the total amount of heavy metals in the functional bacterial agent group(group B)was slightly lower than that in the commercial bacterial agent group(group A).2.High-throughput sequencing of compost samples from different treatment groups showed that there were no obvious differences in microbial diversity and richness in the treatment groups with the same litter ratio and different bacterial agents.In the high temperature period,the dominant bacteria such as Bacillus and Pseudomonas accounted for a relatively large proportion,and then the proportion gradually decreased as the composting temperature decreased.The abundance of dominant bacteria such as Bacillus at the order and genera levels in the functional bactericide group(group B)was increased compared with that in the commercial bactericial agent group(group A),and the copy number of genes related to amino acid,carbohydrate and lipid metabolism was increased during the fermentation process.3.The results showed that the organic carbon content of each group decreased to492.1～518.7 g/kg compared with the initial stage,and the total nitrogen content increased by 35.05%～69.54%,among which the treatment with olive pomace and functional bacteria increased higher.There was no significant difference in the total phosphorus content of the functional fungicial agent group(Group B)before and after fermentation,and the total potassium content of the olea pomace accounted for 25% at the end and the total potassium content of the functional fungi agent treatment(B3 group)was the highest(9.43 g/kg).The addition of oil olive pomace can reduce the nitrate nitrogen content in the fermentation litter,while the addition of oil olive pomace and nitrogen-fixing phosphorolytic potassium bacteria can increase the ammonium nitrogen content of the ectopic fermentation litter.4.The study found that the chloride ion content of compost in the functional fungi group(Group B)was 2.13～2.41 g/kg,which was generally lower than that of the commercial fungial agent group(Group A)of 2.64～3.29 g/kg.At the same time,the sodium content of compost was gradually increased by the addition of olive pomace and functional fungicide,of which olive pomace accounted for 25% and the sodium content of the treatment(B3 group)with functional fungi was the highest,which was 7.91 g/kg.The calcium and magnesium contents of each group in the test group first increased and then decreased,and the application of nitrogen-fixing phosphorolytic potassium bacteria increased the calcium content in the compost,while the magnesium content in the treatment group with olive pomace was lower than that in the treated group without added olive pomace.When the proportion of olive pomace reached 25%,the sulfur content in the composting process showed a significant increase trend,and the sulfur content was higher in the treatment without nitrogen-fixing phosphorolytic potassium bacteria(A3 group).5.After applying rotten fertilizer with 25% of olive pomace and functional fungicide(B3 group)into the soil of the pot,the physical and chemical indexes were determined and it was found that the contents of soil organic carbon,alkaline hydrolyzable nitrogen,available phosphorus and available potassium were significantly higher than those in the control group.The activities of urease,sucrase,catalase and the number of microorganisms in soil were significantly increased.The contents of arsenic,chromium,cadmium and nickel in soil increased by 0.007～0.843 mg/kg compared with the control group.The results showed that replacing part of sawdust bran husk with olea pomace and adding microbial agents with the function of nitrogen fixation and phosphorus hydrolysis in the ex-situ fermentation of pig manure could increase the fermentation temperature and high temperature maintenance time,effectively reduce the loss of nutrients during compost fermentation,improve the quality of compost,increase the abundance of dominant bacteria and the gene copy number related to bacterial amino acid,carbohydrate and lipid metabolism during fermentation at the target and genus levels,and improve the fermentation effect.olea pomace)fermentation works best.At the same time,the rotted fertilizer has a good improvement effect on soil quality,and after the rotted fertilizer is applied to the soil,a certain amount of exogenous heavy metal elements enter the soil environment,which increases the total amount of heavy metals in the soil.