The hormone like effect of earthworm casts on plant growth.

The fertilizing effect of earthworm casts depends on microbial metabolites, mainly growth regulators. The hormone-like effect of earthworm casts is discussed with reference to the literature and ad hoc experiments. When used in plant propagation, earthworm casts promote root initiation and root biomass and increase root percentage. When applied as a casing layer, earthworm casts stimulate carpophore formation in Agaricus bisporus, and N assimilation. When used in horticulture, earthworm casts have a hormone-like effect, influencing the development and precociousness of plants or inhibiting them. These effects are dependent on dose, application time and plant species. In addition, results recorded on dwarfing, stem elongation and precociousness of flowering suggest that the biological effect of earthworm casts is linked to microbial metabolites that influence plant metabolism, growth and development.