40 / 2023-04-30 18:18:45

Assessment of nutrient properties and exploration of organic matter structure characteristics and microbial community characteristics of common vermicomposts in China based on fluorescence spectroscopy and high-throughput sequencing

earthworm; sludge; cow dung; maturation; humic acid; organic fertilizer

In order to scientifically evaluate the potential of vermicomposting products as bio-organic fertilizer under different substrate conditions, 37 vermicompost samples including sludge (S), cow dung (C) and mixed (M) vermicomposts were collected from all over the country to evaluate the nutrient content level and explore organic matter structure and microbial community characteristics, and conduct a comprehensive assessment of nutrient value. The results showed that, the organic matter content of 50.00% sludge vermicomposts, 31.76% cow dung vermicomposts and 50.00% mixed vermicomposts in this study met the latest national standard for organic fertilizer. While the water-soluble nitrogen content reached 3175.24 mg/kg, 1478.79 mg/kg and 3293.97 mg/kg, respectively. And the water-soluble phosphorus content reached 674.55 mg/kg, 526.13 mg/kg and 563.30 mg/kg, respectively. The results of the volumetric integration of three-dimensional fluorescence map showed that the humification degree of organic matter in sludge vermicomposts was the highest, and humus and protein substances increased and decreased by at least 10% compared with the other two, respectively. At the same time, parallel factor analysis revealed that the relative contents of humic acid and fulic acid up to 1.47, 0.73 and 0.91, and tyrosine and tryptophan up to 0.60, 0.86 and 0.73, respectively. The results of high-throughput sequencing showed that the abundance of dominant bacteria in sludge vermicompost was the highest, namely Proteobacteria (38%), Bacteroidetes (18%), actinobacteria (19%) and Firmicutes (18%). The results suggest that the nutrient content of sludge vermicomposts was the highest, followed by mixed and cow dung vermicomposts. The maturation degree of sludge vermicomposts were higher than the other two, but its dispersion degree was highest and it was greatly affected by external environment. The microbial co-occurrence networks of sludge vermicomposts is the densest, its community composition is the most complex, and the structure of microbial community is more stable and orderly.