Influence of inoculants on content and quality of humus during chicken manure composting

Abstract: The aim of this study was to investigate the influence of inoculation on the humification (composition, content and quality) in aerobic composting of chicken manure.Two treatments with three replicates were conductedto achieve the object. The "VT-1000"microbial agent (produced by Beijing VOTO Biotechnology Corporation Limited) was used in composting with the amount of 3‰ of initial raw materials (based on wet weight). A control treatment (CK) was also studied without inoculants. Both of the two treatments had the same C/N ratio (15), moisture content (65%) at the beginning of the composting. The research was conducted in 2m×1.5m×1m(length×width×height) windows using static fermentationcomposting system with natural ventilation for a period of 53 days in total. During the experiment the content of total organic carbon (TOC), total humus (HS), free humus (FHS), water-soluble humus (WSHS), humic acid (HA), fulvic acid (FA) and E4/E6were determined, and some other polymerization and humification indices such as humification ratio (HR), humification index (HI), ratio of humic acid to fulvic acid (HA/FA), percentage of humic acid (PHA) were also studied. Results showed that inoculants significantly affected the humification. Microbial agent could significantly accelerate the organic matter degradation speed and shorten the mineralization phase for about 14 days compared with the CK. Composting with inoculants showed a significant effect on carbon conservation.The TOC of product in inoculated treatment was 16.1% higher than in CK. At the same time, composting with inoculants could elevate the contents of HS by 38.7%, and it also increased FHS, WSHS and HA by 45.7%, 39.0% and 54.9%, respectively.The content of FHS and WSHS decreased in CK after composting, while this trend was converted to increasein inoculated treatment. So the activity part of humus improved with the addition of microbialagent. Despite the content of HS decreased, the HR, HI, HA/FA and PHA were all increased at the end of composting especially in the composting with microbial agent, indicating that composting can improve the humus quality. HA/FA was higher in inoculated treatment than in CK which indicated that inoculants can accelerate the compost maturity. The E4/E6 value in the microbial agent treatment was lower than that in the CK treatment, which indicated that adding microbial agent enhanced the extent of humification and aromatization in the compost. In conclusion, inoculants could shorten the composting time, increase the content of humus and enhanced the extent of humification and aromatization in the compost.