Influences of vermicomposts on field strawberries: part 2. Effects on soil microbiological and chemical properties.

The effects of applications of food waste and paper waste vermicomposts on some soil chemical and biological properties were evaluated in field plots planted with strawberries. Six-week old strawberries (Fragaria ananasa, var. Chandler) were transplanted into 4.5 m(2) raised beds under a plastic tunnel structure measuring 9.14 x 14.6 x 3.6 m. Vermicompost were applied at rates of 5 or 10 t ha(-1) supplemented with inorganic fertilizers to balance fertilizer recommendations for strawberries of 85-155-125 kg NPK ha(-1). Effects of vermicomposts on strawberry growth and yields have been reported previously [Arancon, N.Q., Edwards C.A., Bierman P., Welch, C., Metzger, J.D., 2004. The influence of vermicompost applications to strawberries: Part 1. Effects on growth and yield. Bioresource Technology 93:145-153]. Total extractable N, NH(4)-N, NO(3)-N and orthophosphates did not differ significantly between treatments, except on the last sampling date (harvest date) in which significantly greater amounts of NH(4)-N, NO(3)-N and orthophosphates (P <or= 0.05) were recorded in vermicompost-treated soils than in the controls. Two major results of vermicompost applications to soils were increases in dehydrogenase activity and microbial biomass-N which were not dose-dependent. Increased dehydrogenase activity and microbial biomass-N was correlated positively with the increased amounts of NH(4)-N, NO(3)-N and orthophosphates in the vermicompost-treated plots than in the controls. Increases in microbial populations and activities are key factors influencing rates of nutrient cycling, production of plant growth-regulating materials, and the build-up of plant resistance or tolerance to crop pathogen and nematode attacks.