Biopotential of compost and compost products derived from horticultural waste—Effect on plant growth and plant pathogens' suppression

•Preparation method had impact on differences in the compost products’ composition.•Compost products demonstrated a diverse effect on plant species’ germination.•Compost products application has a potential in the suppression of plant pathogens.•Green waste composting represents a promising approach in sustainable horticulture. Besides ecological and environmental benefits of green open spaces, horticultural waste management has various environmental consequences. Green waste composting represents promising environmentally friendly alternative which gives valuable products with positive soil and plants impact. Composting products’ quality determinates their application and depends on the particular waste material and process parameters. The aim of this paper was to estimate the chemical and microbiological quality of green waste compost and compost products (compost tea, compost extract and the solid phase after extraction), and their biopotential based on germination rate, germination index and inhibition of phytopathogenic fungi growth. Higher germination rate of examined plant seeds was noticed on the solid phase after extraction, and compost extract, compared to compost, and compost tea, respectively. Plants with low germination rate grown on compost showed higher fresh and dry biomass. Compost products strongly inhibited the growth of plant pathogens Fusarium oxysporum, Rhizoctonia sp., and Pythium debaryanum. Presented results show that composted biodegradable waste from urban green spaces contribute to the plant growth and phytopathogenic fungi suppression, and thus improve the overall environmental quality.