Effect of biochar on bacteria community structure of pig manure composting

Abstract:

[Background] The bacterial community diversity affected the composting process and biochar affected the growth of bacteria, but the effect of biochar on the bacterial community structure of pig manure composting has not been reported yet. [Objective] According to the variation of bacterial community structure and composting temperature, adequate content of biochar was added to pig manure composting to improve the proportion of major bacteria and composting efficiency of pig manure composting, so as to provide reference for the joint application of biochar and pig manure composting. [Methods] The biochar content of 0%, 3%, 6% and 9% was set, and four levels of biochar were selected in the high-temperature period and the stable-temperature period of composting process, respectively. According to the Illumina MiSeq’s high-throughput sequencing results of bacterial 16S rRNA gene, the effects of biochar content and composting temperature on bacterial community structure of pig manure composting were analyzed. [Results] At the phylum level, the major bacteria with the highest abundance in pig manure composting were Proteobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Gemmatimonadetes, Firmicutes, Acidobacteria and Deinococcus-Thermus. At the genus level, the major bacteria with the highest abundance in pig manure composting were Chryseolinea, Subgroup_6_norank, Steroidobacter, Anaerolineaceae, Nonomuraea, Longispora, Bacillus, Sporacetigenium, Luteimonas, Phyllobacteriaceae, Truepera, Rhodothermaceae and Aquamicrobium. The change of biochar content could promote or inhibit the growth of major bacteria in pig manure composting. As the content of biochar increased, the abundance of Bacillus, Streptomyces, Rhodothermaceae and Firmicutes increased, whereas the abundance of Chryseolinea, Longispora and Steroidobacter decreased. At the high-temperature composting period, the abundance of Firmicutes, Bacillus and Streptomyces was greater than that of the stable-temperature composting period; while Chloroflexi, Anaerolineaceae and Longispora were opposite. The number of bacterial community in high-temperature composting period was up to seventy, significantly greater than stable-temperature composting period of fifteen. Among them, the number of bacteria played a major role in pig manure composting was up to seven (Rhizobiales, Incertae_Sedis, Proteobacteria, Alphaproteobacteria, Xanthomonadales, Gammaproteobacteria and Steroidobacter) in the high-temperature period, while only three (Micromonosporales, Longispora and Micromonosporaceae) were found in the stable-temperature period. The bacterial diversity of pig manure composting in high-temperature period was significantly higher than that of stable-temperature period. After adding biochar to pig manure composting, environmental factors (electrical conductivity, water content, temperature and pH) had no significant effect on the major bacteria of pig manure composting. β-Proteobacteria, Rhodothermaceae, Phyllobacteriaceae and Bacterium were significantly affected by the water content, temperature and pH. [Conclusion] The content of biochar and composting temperature could change the bacterial community structure of pig manure composting, and significantly increase the number and diversity of bacteria in pig manure composting at the high-temperature period. The electrical conductivity, water content, temperature and pH of pig manure composting could affect the growth of composting bacteria, but the effect on the major bacteria with the highest abundance in pig manure composting was not significant.