Influences of vermicomposts on field strawberries: 1. effects on growth and yields

Vermicomposts processed commercially from food wastes and paper wastes were applied, to 4.5 m(2) field plots, under high plastic hoop tunnels, at rates of 5 or 10 tha(-1) to evaluate their effects on the growth and yields of strawberries (Fragaria ananasa) var. 'Chandler'. The vermicomposts were incorporated into the top 10 cm of soil and supplemented, based on chemical analyses, with amounts of inorganic NPK fertilizers calculated to equalize the initial fertilizer rates of 85-155-125 kgha(-1) NPK applied to the inorganic fertilizer plots. All treatments were replicated four times, in a completely randomized design, at two field sites on Doles silt loam or Hoytville silty clay loam at Piketon and Fremont, Ohio, respectively. Vermicompost applications increased strawberry growth and yields significantly; including increases of up to 37% in leaf areas, 37% in plant shoot biomass, 40% in numbers of flowers, 36% in numbers of plant runners and 35% in marketable fruit weights. These responses seemed not to be dose-dependent, since strawberries at one site grew fastest and yielded most in response to the 10 tha(-1) vermicompost application rate, whereas they responded positively and similarly to both the 5 and 10 tha(-1) rates of applications at the other site. These responses could not have been mediated by availability of macronutrients, since all plots were supplemented with inorganic fertilizers, to equalize macronutrient inputs for all treatments, but based on other research in our laboratory could have been due to production of plant growth regulators by microorganisms during vermicomposting.