• Two goals this week: add more food residues (to increase microbial diversity) to the two new vermicomposting beds described in last week’s blog and apply the vermicompost that is finished to the orchard or to tomatoes.

• The two new vermicomposting beds have been constructed using horse bedding. In addition to the horse bedding, each bed will receive in the next few days about 315 lbs of fruit that is being discarded (it can’t be sold because it is blemished or damaged; kitchen fruit scraps). The fruit is kept in 5 gallon buckets then water is added and the fruit is broken up with a hoe. The buckets are kept in the sun and this starts the process of decompostion (even fermentation). This pre-composting step is necessary because adding fruit residues that are not decomposed directly to the vermicomposting beds is nothing more than thermophilic composting resulting in high temperatures and potential death of the worms. The pre-composted fruit material is soft and is full of active microbes.

• The vermicomposting process can be divided into three different phases. Small undigested fruit material and the microbes associated with it are first ground up in the crop and gizzard  of the worm and then the material transits through the intestine of the worm where it is processed: a complex interplay between the enzymes and mucus secreted by the worm’s digestive system (which includes other microbes). Some microbes in the worm gut secrete enzymes that can degrade cellulose and phenolic compounds. This is why we add shredded Frog Hollow cardboard boxes to the worm beds in order to produce vermicompost that is fungal dominated and thus well suited for fruit trees.

• Upon completion of the worm gut associated decomposition process, the resulting casts (“worm poop”) undergo further decomposition under the indirect influence of the worm. As the casts travel through the worm gut, they get covered with mucus which is a source of carbon. The excreted mucus covered casts continue digesting soil or compost organic material. During this curing/aging process as it is called , the vermicompost reaches its optimum in terms of biological properties that promote plant growth and suppress plant diseases.

• We do not know when this optimum is reached and we don’t know if there is some kind of “expiration date”. We believe that most likely the optimal quality is reached only in the natural ecosystem on the farm. That is why we keep the finished piles watered and we want to get them out into the field as soon as possible where the aging process can do its work.

• At the present time the vermicompost will be applied to a new  part of the orchard where there are some young peach trees that have a growth problem (they are smaller than their colleagues of the same age). The vermicompost will be applied around the trees (not too close to the trunk) and overlaid with our thermophilic compost made on-site.

• We will also apply vermicompost to tomatoes and vegetables. However, first this vermicompost will be made more bacterial (rather than fungal) because vegetables and tomatoes prefer a more bacterial soil (ratio of fungi to bateria less than one. The biology will have to be analyzed carefully.

• We are still working on our irrigation problems of the vermicomposting beds. Because of the extreme dryness in Brentwood, the beds behave like coffee grounds in a filtering device.  You have to have the right particle size, you can’t overwater or the water drains too fast , you have to water slowly. Also, we want to reduce the watering of the beds as much as possible because of the drought; the worms are very cooperative at maintaining the right moisture content once good conditions are established. But I am used to it, because I am a coffee fanatic. More on that in the future.

Author: 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.