Effect of Vermicompost on Nitrate Leaching and Plant Growth in Specialty Crop Production.

The use of vermicompost is suggested as a method to reduce nitrogen (N) losses in crop production; however, it is unclear whether and how vermicompost can affect water quality after a significant irrigation or rainfall event. The objectives of this experiment were to: a) determine the concentration of nitrate-nitrogen in drainage water from vermicompost-amended media planted with strawberry (Fragaria x ananassa var. “Portola”) in a greenhouse setting and b) to determine vegetative biomass of strawberries grown in vermicompost-amended media. Bare-root strawberry plugs were grown in individual one-gallon plastic pots. The treatments consisted of two media: 1) a peat:perlite soil-less mix and 2) a fine sand soil. Each media was amended with three levels of dairy manure vermicompost:  0%, 10%, 25% by weight, and a biweekly synthetic fertilizer treatment of 150 mg N-P-K L^-1. All treatments were evaluated in a full factorial randomized block design. Drainage water from each plant was collected each week for 18 weeks and analyzed for NO₃^- concentration. In the first two weeks, we observed high (1000-5000 mg L^-1) amounts of NO₃^- leaching across all vermicompost -amended media relative to non vermicompost-amended media, but this leaching significantly (p<0.01) decreased over time across all vermicompost treatments. High initial NO₃^- leaching may have been a consequence of vermicompost feedstock (cow manure), which is high in soluble N, and the rates of application used in this experiment. Plants grown with vermicompost at 25% with synthetic fertilizer had the highest above-ground vegetative biomass (15.3 g) relative to plants with synthetic fertilizer alone (5.3 g). These data suggest vermicompost addition rates of 10% and 25% by weight promote high vegetative biomass in greenhouse strawberry but may facilitate high initial nitrate leaching, which can negatively affect water quality and environmental health.