Vermicomposting vs Composting
   

A COMPARISON OF VERMICOMPOSTING AND COMPOSTING



Jorge Dominguez, Clive Edwards and Scott Subler are with The Soil Ecology Laboratory, The Ohio State University in Columbus. A future report by them will discuss operational experiences at commercial vermicomposting facilities.

TESTING THE IMPACT OF VERMICOMPOSTING
AN EXPERIMENT at the Soil Ecology Laboratory of Ohio State University studied a continuous vermicomposting process for different mixtures of pig manure slurries and agroforestry by-products. The research project analyzed the effects of earth-worm populations on the process and also evaluated the vermicomposts produced at different times. Biosolids and pig manures -when mixed with bulking agents -are probably the most productive residuals for growing earthworms. Covered wooden boxes with drainage holes to avoid leach ate accumulation were filled with a layer of digested vermicompost (air dried). On top of this layer, a 0.5 cm wire mesh - which allows earthworm migration - was placed and additional layers of pig manure/bulking agent mixture were added, separated by the same type of wire mesh. Every 2-1/2 to three months, the boxes were sampled, noting numbers and total weight of earthworms and cocoons. A subsample of each layer was taken to determine several physical and chemical parameters of the fresh samples and chemical ones after air dried.

NITROGEN AND HUMIFICATION IN VERMICOMPOSTING
As regards total nitrogen, in all treatments and also at the different times,
the net content decreased - being more marked at the final stages when earthworm activity was higher. The different nitrogen fractions followed a similar tendency to the total nitrogen. In all treatments, at the final stages of the process, when the earthworm population was bigger and active, important reductions of the organic nitrogen content and a high nitrification rate were observed. The nitrification was 50 to 65 percent higher in the earthworm treatments than in the controls.

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