Understanding the Shift in the Microbiome of Composts That Are Optimized for a Better Fit-for-Purpose in Growing Media

Abstract

Three characteristics are considered key for optimal use of composts in growing media: maturity, pH and organic matter content. Maturation is a critical step in the processing of composts contributing to compost quality. Blending of composts with chopped heath biomass, sieving out the larger fraction of composts and acidification of composts by adding elemental sulfur may be used either to increase organic matter content or to reduce pH for a better fit in growing media. While several studies have shown the effectiveness of these treatments to improve the use of composts in growing media, the effect of these treatments on the compost microbiome has merely been assessed before. In the present study, five immature composts were allowed to mature, and were subsequently acidified, blended or sieved. Bacterial and fungal communities of the composts were characterized and quantified using 16S rRNA and ITS2 gene metabarcoding and phospholipid fatty acid analysis. Metabolic biodiversity and activity were analyzed using Biolog EcoPlates. Compost batch was shown to be more important than maturation or optimization treatments to determine the compost microbiome. Compost maturation increased microbial diversity and favored beneficial microorganisms, which may be positive for the use of composts in growing media. Blending of composts increased microbial diversity, metabolic diversity, and metabolic activity, which may have a positive effect in growing media. Blending may be used to modify the microbiome to a certain degree in order to optimize microbiological characteristics. Acidification caused a decrease in bacterial diversity and microbial activity, which may be negative for the use in growing media, although the changes are limited. Sieving had limited effect on the microbiome of composts. Because of the limited effect on the microbiome, sieving of composts may be used flexible to improve (bio)chemical characteristics. This is the first study to assess the effects of maturation and optimization treatments to either increase organic matter content or lower pH in composts on the compost microbiome.

Composted Municipal Green Waste Infused with Biocontrol Agents to Control Plant Parasitic Nematodes—A Review

“…The composting process furthers decomposition, and through mixing, sieving and in many cases, acidification, compost matures and thus, its microbial composition changes. As Pot et al (2021) [162] observed, among the variables, raw materials had the highest influence on the microbiome of the end product. While the maturation of compost definitely increased microbial diversity, blending and acidification are tools that modify and optimise the compost microbiome.…”

Bacterial Enrichment Cultures Biotransform the Mycotoxin Deoxynivalenol into a Novel Metabolite Toxic to Plant and Porcine Cells

“…At last, the effect of enrichment of product B was tested using the edgeR package (version 3.28.0) [ 93 ] as described in detail in De Tender et al [ 94 ]. According to Pot et al [ 95 ], normalization based on the trimmed mean of M-values (TMM) was applied to correct for differences in library size of the count table. A design matrix was defined based on the experimental design.…”

Vertical Farming: The Only Way Is Up?

“…Composted materials such as composted bark and green waste compost have a much more diverse microbial community than other plant-growing media materials [50,65]. The compost feedstock is an important determinant of the compost microbiome, and compost maturation increases microbial diversity, favoring beneficial microbes [65].…”

“…Composted materials such as composted bark and green waste compost have a much more diverse microbial community than other plant-growing media materials [50,65]. The compost feedstock is an important determinant of the compost microbiome, and compost maturation increases microbial diversity, favoring beneficial microbes [65]. In addition, composts have disease-suppressive properties linked to the compost's high microbial activity and the presence of beneficial microbes such as Trichoderma, Pseudomonas, Pantoea, and Bacillus spp., which are known to contribute to the biocontrol effect [65].…”

“…The compost feedstock is an important determinant of the compost microbiome, and compost maturation increases microbial diversity, favoring beneficial microbes [65]. In addition, composts have disease-suppressive properties linked to the compost's high microbial activity and the presence of beneficial microbes such as Trichoderma, Pseudomonas, Pantoea, and Bacillus spp., which are known to contribute to the biocontrol effect [65]. These studies suggest that a diverse and competitive microbiome in the plant-growing medium provides functional diversity and resilience to the environment.…”