Influences of field applications of vermicomposts on soil microbiological, chemical and physical properties and the growth and yield of strawberries, peppers and tomatoes

Vermicomposts are stabilized organic matter produced through the biological degradation of organic wastes by interactions between earthworms and microorganisms. Vermicomposts produced from food waste and paper wastes were applied at the rate of 10 and 5 t/ha to soils planted to strawberries. Food waste, paper waste and cow manure vermicomposts were applied to pepper and tomato plots at the rates of 20 t/ha and 10 t/ha in 1999 and at rates of 10 t/ha and 5 t/ha in 2000. Control plots were treated with inorganic fertilizers only and all vermicompost-treated plots were supplemented with inorganic fertilizers to equalize available N levels in all plots on the transplanting date. Leaf areas, numbers of strawberry suckers, numbers of flowers, shoot marketable fruit yields increased significantly in plants that received treatments compared to those strawberries and peppers that received inorganic fertilizers only. Food waste vermicomposts had greater effects on growth and yields of strawberries than paper waste vermicomposts whereas paper waste and cow manure vermicomposts had greater effects on peppers and tomatoes. The tomato fruit yields in the vermicompost plots were usually greater but not statistically different from the yields in the inorganic plots. Increases in growth and yield were not dose dependent. There were increases in the total extractable N, microbial biomass and orthophosphates in the vermicompost-treated plots. There were more fungivorous and bacterivorous nematodes in soils that were treated with vermicomposts than the inorganic control and there were more plant-parasitic nematodes on soils that received inorganic fertilizers only than in vermicompost-treated soils. Verticillium wilt disease in strawberries was suppressed significantly in soils treated with vermicomposts.; The improvements in growth and increases in yields could not be explained solely by the availability of macronutrients because their amounts were equalized in all plots at transplanting time. Changes in the amounts of microbial biomass, dehydrogenase activity and nematode trophic compositions could possibly be linked to the increases in the growth and yield of strawberries, peppers and tomatoes. Additionally, growth and yields could have been due to growth regulators in the vermicomposts.