Dual-Purpose Vermicompost for the Growth Promotion and Suppression of Damping-Off Disease on Potted Vegetable Soybean

Vermicompost is applied as a soil amendment to promote plant growth and yield. It also helps to significantly reduce the incidence of soil-borne diseases. However, its efficiency depends on the type of earthworm from which it is formed. The current study aims to compare the effects of two vermicompost types derived from African nightcrawler (AF) and Tiger worm (TG) as a soil amendment to evaluate its potential for suppressing damping-off disease both in vitro and in vivo. It also aims to determine the effects of both vermicompost types on the growth and yield-related traits of potted Thai vegetable soybean [Glycine max (L.) Merrill] variety “Chiang Mai 84–2” grown under greenhouse conditions when amended to the soil at various application rates (1%, 2%, 3% w/w). AF vermicompost exhibited better suppression of damping-off disease than TG vermicompost in vitro and under greenhouse conditions. AF vermicompost performed significantly greater suppressive efficacy on the mycelial growth of Athelia rolfsii in vitro than TG vermicompost, indicated by 50% and 16% inhibition, respectively. Damping-off incidence on vegetable soybean seedlings grown in soil amended with AF vermicompost was significantly lower (21%) than in soil amended with TG vermicompost (32%) under greenhouse conditions. With an increased application rate of 1% to 2% or 3% for each vermicompost type, plant yields significantly enhanced, with no significant variations among the 2% and 3% rates. Applying vermicompost at 2% w/w through soil amendment was the appropriate rate for promoting the growth and yield of potted vegetable soybeans. The results can be used to guide the application of vermicompost to control soil-borne plant diseases, promote plant growth, and enhance yields, especially in terms of organic crop production. Further research is needed to evaluate its potential for other potted crops and protect against soil-borne diseases.