Effects of partial replacement of sawdust and bran by olive pomace on ectopic fermentation of swine manure

【Objective】This research evaluated the fermentation effect of olive pomace partially replacing traditional mattress materials made by sawdust and bran and using functional microbial inoculum for ectopic fermentation,so as to provide reference for swine manure ectopic fermentation and the resource utilization of agricultural waste.【Method】Six different combinations of mattress materials and microbial inoculum were used in the experiment. The different combinations of mattress materials and microbial inoculum were thoroughly mixed with swine manure for composting and fermentation. Samples were taken on the day 0, 5, 10, 15, and 20 of fermentation to measure temperature,moisture,pH,conductivity, nitrogen content, phosphorus content, potassium content, and microbial diversity of each treatment. The differences in physical and chemical indicators and microbial community changes of each treatment were compared and analyzed to evaluate the fermentation effect of adding olive pomace and microbial inoculum.【Result】The addition of olive pomace and microbial inoculum could increase the temperature of ectopic fermentation and the duration of high temperature. The pH value of each group increased,while the water content and EC value increased first and then decreased. During the 0-20 day fermentation process,there were differences in the trend of changes in organic carbon,nitrogen,phosphorus, and potassium contents among different treatment groups. Compared with the day 0 of fermentation,the organic carbon content significantly decreased on day 20 of fermentation(P<0.05,the same below). The total nitrogen content significantly increased. The total phosphorus content of the group adding microbial inoculum showed no significant difference before and after fermentation(P>0.05). The total potassium content was significantly reduced,and the total potassium content in the group of 45% sawdust+30% bran+25% olive pomace +functional microbial inoculum was the highest(9.43 g/kg). The addition of olive pomace could reduce the nitrate nitrogen content in the fermentation mattress material,while the addition of olive pomace and functional microbial inoculum could increase the ammonium nitrogen content in the ectopic fermentation mattress material. During fermentation,the abundance of dominant bacteria such as Bacillus at the order and genus levels in the group adding microbial inoculum increased,and the addition of olive pomace could increase the copy number of metabolism-related genes of amino acid,carbohydrate and lipid in bacteria.【Conclusion】 Olive pomace can partially replace the sawdust and bran mattress material,and the composition of 45% sawdust+30% bran+25% olive pomace combined with functional microbial inoculum is more conducive to the decomposition of fermentation mattress and the formation of organic fertilizer.