The 2010 ASHS Annual Conference

Application of aqueous extract of vermicompost has been shown to improve plant health, yield and nutritive quality. Few studies have been conducted to determine the effect of vermicompost extract on soil biological properties. The objective of this study was to evaluate the independent effects and interaction between vermicompost extract and soil type on plant growth, mineral nutrient concentration, phytonutrient content and soil biological properties. Pak-choi plants were grown in Oxisol (series), Mollisol (series) and peat based media fertilized with commercial green waste thermophilic compost. Vermicompost extracts were prepared with various extraction methods using 1:10 chicken manure based vermicompost to water dilution and applied weekly at the rate of 200 mL per plant for four weeks. Application of vermicompost extract regardless of extraction methods enhanced plant production, total root length, root surface area, mineral nutrient content, total carotenoids and total glucosinolates in plant tissue across the soil type. Vermicompost extract had negative effect on total phenolics compared to that of mineral nutrient solution and control. All vermicompost extracts regardless of extraction methods provided equivalent effect on plant growth and nutrient concentration in peat based media. However, aerated vermicompost extract with microbial enhancer had smaller effect on plant growth and nutrient concentration compared to that of aerated vermicompost extract and non aerated vermicompost extract in both soils. Greater effect of vermicompost extract over mineral nutrient solution suggests contribution of additional factors besides mineral nutrition. Vermicompost extract improved mineral nutrient status and microbial properties of Oxisol, Mollisol and peat based media. Dehydrogenase activity of vermicompost extract treated soil (133 µg TPF g^-1 soil) was approximately 45% higher than that of not treated soil (90 µg TPF g^-1 soil). Vermicompost extract effect on soil respiration (CO₂ Fluxes µmol m^-2sec^-1) was generally similar to that of dehydrogenase activity. Moreover, the dehydrogenase activity was positively correlated (r = 0.64) with the soil respiration. The findings of this study suggest that vermicompost extract can serve multiple purposes including supplemental source of plant nutrient and enhancing soil biological properties.