Organic farming may not be high on the list of most vegetable production operations, but research by a team of USDA-National Agricultural Research Center plant and soil specialists indicates vermicompost used in greenhouse tunnels not only helps reduce production costs by eliminating the need for chemical fertilizers, it also significantly increases yield and plant health of hybrid hothouse tomatoes.
Vermicompost is a high nutrient compost made up primarily of carbon (C), hydrogen (H) and oxygen (O) and contains nutrients such as NO3, PO4, Ca, K, Mg, S, and other micronutrients that exhibit similar effects on plant growth and yield.
For the purpose of the NARC research, different plant materials — including plant waste — were collected and mixed with cattle manure at a 2:1 ratio (100 kg plant material and 50 kg of manure). Healthy and adult earthworms (Eisenia fetida) were allowed to feed on the mixture and converted it into vermicompost after about 60 days.
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Research results indicate vermicompost significantly improved yield by increasing both numbers and size of tomatoes produced. Researchers say higher yields and size were probably due to vermicompost having more readily available nutrients and growth-regulating substances such as urease, phosphomonoesterase, phosphodiesterase, and arylsulphatase.
They concluded that the significant increase in yield and fruit quality of L. esculentum was most probably attributed to improved uptake of N, P, and K from vermicompost, as well as increased chlorophyll production in the leaves of the tomato plants. In addition, vermicompost increased microbial populations with production of plant-growth-influencing materials and buildup of plant resistance or tolerance to crop diseases and nematode attacks.
While the NARC research, conducted at a research center in Pakistan, was limited to greenhouse tunnel applications, researchers suggest vermicompost could be readily produced in arable land beds in crop fields.
Clive Edwards, Ohio State University entomologist and author of Earthworm Ecology, says the use and production of vermicompost is not limited to greenhouse applications, but is also adaptable to arable land use, provided conditions are met to entice earthworms in sufficient numbers to become active in local crop soils.
Those conditions include increasing the quality of natural habitat for earthworms and providing proper nutrients to sustain earthworm populations in soil.
In a vegetable field, this can be accomplished by creating areas of natural habitat for existing earthworm varieties, or for types of earthworms — night crawlers for example — introduced into soil. Night crawlers are the same type of worms sold as fishing bait.
This may be best accomplished by using areas between widely-spaced squash or melons, or other types of vegetable crops, to create habitats. Soil between furrows or between plants can be mulched, and a single sheet of newspaper can be placed over the mulched soil, followed by a layer of oatmeal, cornmeal, or other suitable fodder for earthworms, and topped by a thick layer of grass clippings or hay. Several such layers can be applied, creating a perfect environment for earthworms to perform their service.
Vermicompost is created as earthworms feed, then move through compost material depositing their castings, a combination of manure and the slime they emit through their skin. Together these deposits enrich the soil with nutrients, while the movement of the worms opens airways and drainage paths that further improve soil health.
Regardless where you farm in North America, earthworms native to your soil environment can be attracted and nurtured to increase population levels, the researchers say. During the winter months, depending on location, earthworms will dig deeper into soils to survive, or farmers can spread thick layers of hay on top of soils to help insulate earthworm habitat, or they can be produced in specially prepared indoor bins or beds that can be kept in a barn or shed.
Bins can be prepared using soil and compost up to about 12 inches in thickness and adding food waste like oatmeal or rice. Adding a couple hundred night crawlers or red earthworms to the mix, and closing the top for around two months to allow the worms to work their magic, should do the trick.
During winter in temperate zones, bins can be buried in holes in the field and covered with a tarp, making it easy to access the vermicompost when needed. The compost also makes a healthy top-dressing for beets or carrots, two crops that respond very well to vermicompost.
The savings on chemical fertilizers and the benefits in healthier soils, plants, and crops, combined with better yields, can more than offset the time required to “go green” on the farm. Smaller farms, particularly, can benefit the most, since using compost versus chemical sprays can also reduce investment in costly equipment.