Next week 429 prune trees will be planted in an area that was a nectarine  orchard until last year. Some of the trees (117 to be exact) will be placed in holes that were filled in December with  immature compost  (produced at Frog Hollow and still very active metabolically) and 250 worms each.  We want to see if  the vermicompost , the end product of vermicomposting,  produced in these planting holes will have positive growth effects on the young trees and this may include replanting problems. Also the method described above is a more efficient way of applying compost to newly planted trees.

Vermicompost is a finely structured material with high porosity and water holding capacity and a low C:N ratio. It contains nutrients in forms that are readily taken up by plants. Vermicompost also contains plant growth hormones produced by microorganisms and plant growth regulators  ( humus-like compounds). In the example we are describing, thermophilic composting and vermicomposting have been combined. Thermophilic composting enables sanitization of residues and elimination of plant  pathogens and weed seeds. Also,  woody materials are decomposed during thermophilic composting relatively fast; decompositon of woody materials in vermicomposting is accomplished by fungi at ambient temperatures and takes a very long time. Thermophilic composting followed by subsequent vermicomposting increases nutrient availability. In addition vermicompost contain more microorganisms and phytohormones than thermophilic composts.

Vermicomposting worms (Eisenia fetida) are litter dwellers and transformers. They live in or near the surface litter in soil organic matter. These earthworms can be considered  small compost piles or mechanical blenders:  small particles of  organic matter (from food residues), microorganisms (from food residues and soil ) are ground up in the crop and gizzard as they pass through the worm. In the intestine of the worm, the travelling material is digested by enzymes and gut bacteria. Even after the material is excreted (casts), the digestion continues  due to the presence of mucus. As in thermophilic composting, microorganisms reproduce and release carbon dioxide, water, organic products and energy in the form of heat. However, based on energetic analyses,  in vermicomposting heat is managed in such a way as to induce heat dissipation rather than accumulation. In vermicomposting,  worms regulate  bacterial and fungal numbers and  as a consequence they help microbial communities use the available energy from organic residues more efficiently.

Christophe Kreis MLF Soil Consulting PhD, Molecular Biology/Developmental Biology, University of British Columbia, Canada. Christophe is co-founder of MLF Soil Consulting with his wife Monique. He started his career in basic medical research and after various positions in academia and industry Christophe slowly returned to his first passion Soil Ecology and Microbiology. It is his belief that human health is tied intimately to soil health through the production of healthy food. For this reason MLF Soil Consulting is committed to help farmers improve the management of their soil through composting, vermicomposting and biological analysis of microbial soil life.

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