Vermicompost significantly affects plant growth. A meta-analysis

Food production and waste management are two increasing issues ensuing from the growing world population. Recycling organic residues into amendment for food production seems to appear as an opportunity to partially solve this double challenge. Vermicomposting is a process whereby earthworms transform organic residues into compost that can be used as a substrate for plant growth. Many studies have evaluated the effect of vermicompost on plant growth, but a quantitative summary of these studies is still missing. This is the first meta-analysis providing a quantitative summary of the effect size of vermicompost on plant growth. We found that vermicompost brought about average increases of 26% in commercial yield, 13% in total biomass, 78% in shoot biomass, and 57% in root biomass. The positive effect of vermicompost on plant growth reached a maximum when vermicompost represented 30 to 50% of the soil volume. The best original material to be used for vermicompost production was cattle manure. The effect was stronger when no fertilizer was added, and lower when the standard Metro-Mix 360 substratum recommended by some authors was used as a growing medium in greenhouse or climatic chambers. Herbs (especially Cucurbitaceae and Asteraceae) and legumes exhibited the largest biomass increase in the presence of vermicompost. These results are discussed through an analysis of potential publication biases showing an over-representation of studies with a high effect size. We finally recommend authors of primary research to provide a minimum set of statistical parameters, output variables, and experimental condition parameters to make it easier to include their work in meta-analyses. Overall, our study provides synthetic information on the beneficial effects of vermicompost for plant growth, which could help bring waste management and agriculture together towards a society with a more circular economy.