February 23, 2005 | General


BioCycle February 2005, Vol. 46, No. 2, p. 47
A steady diet of composted cow manure, corn/soybean feed, cotton gin residuals and brewery mash over 12 years generates thousands of tons of worm castings.
Jason Governo and Britt Faucette

LOCATED in the small community of Douglas, Georgia, Bear Creek Worm Farm is rated by many as the largest vermiculture and vermicomposting operation in the southeastern United States. Owned and operated by Jack and Lucy Brantley since 1992, the farm has been mainly producing red wiggler worms for the region’s fishing bait market as well as thousands of tons of castings for the nursery industry.
The concept began when Jack discovered worms feeding in an aged stack of peanut hay on his farm where the Brantleys raised hogs. His idea was to start raising worms to supplement their retirement income. After many hours of library research, 100 pounds of Little Reds and Blue Wigglers were bought and set up in an unused hog barn.
After initial production struggles, his small stock began growing and reproducing to the point where it could be marketed. Gross revenue from sales of red wigglers the first year was approximately $13,000. Sales continued to double for the next three years as he expanded his market to cover northern Florida, southern Alabama and southern Georgia. The original 100 pounds have grown into about 15,000 pounds of worms. The original small hog barn no longer contains his worms as he has now spread into old poultry houses and outdoor shade structures covering nearly three acres.
Over the past 12 years, he has experimented with a variety of diets to come up with the best combination that balances feed availability and cost, ease of application, and worm growth response. The recipe that he currently uses is a combination of commercial corn and soybean feed, composted cow manure, partially composted cotton gin residuals, aged sawdust (over 10 years) and brewery mash from a local beer producer. Bear Creek’s 7.5 tons of worms have a voracious appetite requiring a 23 ton dump trailer load of brewery mash delivered every week, hundreds of cubic yards of cotton gin residual obtained during the fall cotton ginning season, and a monthly semitruckload delivery of dairy manure. With no automation or special delivery systems, Brantley and two laborers feed the worms approximately 25 tons of feed per week.
In addition to growing worms, Brantley has been processing some of the highest quality worm castings available in his part of the country. Understanding that it can take years to produce a substantial quantity of castings, Brantley waited almost 10 years before marketing castings from his farm in order to establish a viable stock and supply for demanding customers. Bear Creek Worm Farm currently stocks 5,000 to 6,000 tons of castings with more being produced each day. When asked why he refused to sell castings until now, Brantley responds: “Anyone can sell a few pounds here and there, but we wanted to have a large enough quantity to attract and sell to a large distributor that would package and market this product regionally or even nationally. We have entertained a few offers but none have been substantial enough for us to seriously consider.”
Unlike compost where thousands of tons can be processed in a month or two, a similar quantity of worm castings can take years. Approximately half the food eaten by worms is turned into castings and like any processing operation, there are management requirements that help to ensure production efficiency. For example, it is critical to determine what volume to feed to a known quantity of worms, during a specific time period, at a predetermined stocking rate, to produce either worm mass or castings efficiently and effectively. In a study conducted at the University of Georgia’s Biological & Agricultural Engineering Department, engineers determined that in order to produce the best castings, the optimum stocking density and feeding rate for red wigglers (Eisenia fetida) was 0.75 kg-feed/kg-worm/day. To generate more worm biomass, a higher stocking density of 1.60 kg-worms/m2 and a feeding rate of 1.25kg-feed/kg-worm/day would be more appropriate.
Worm castings have long been touted as one of the highest quality forms of humus. Castings are high in organic matter and can be higher in nutrient content than traditional composts. The high level of organic matter content ensures good water holding capacity and a slow release of nutrients are better suited for plant uptake and reduce potential nutrient loss compared to commercial fertilizer. Worm castings can also provide trace minerals, essential for healthy plant growth, which most fertilizers do not provide.
Additionally, worm castings can increase soil biota, as beneficial bacteria and fungi can increase nutrient availability and uptake. Longtime nurseryman, Mike Cunningham, owner and operator of Country Gardens Nursery in Newnan, Georgia – a suburb of Atlanta – has considered using earthworm castings to replace all commercial potting soil in his nursery operation. Seeing first-hand the market trend toward organic vegetable production, Cunningham says: “More and more people want to buy or grow their own food without all the chemical fertilizers that normally accompany agriculture.”
Cunningham was encouraged to contact Bear Creek Worm Farm by Skip Glover, a well known Georgia organic farmer who uses Bear Creek’s castings in his own organic vegetable production. Cunningham immediately started experimenting with Bear Creek’s castings in his transplant mix in the summer of 2004. His greatest concern with using castings was the same as “….all greenhouse people, they want to be sure that their pots drain well. The castings were dark and spongy looking and that normally translates into fungus problems. I was initially worried about pore space and drainage but the castings didn’t seem to be a problem at the mix ratios we used. They drained and had no problem. I needed to make sure that they drained before I started doing all my transplants in the castings.”
Encouraged by preliminary results in his transplants, Cunningham planted all his fall vegetables, including lettuce, collards, cabbage, broccoli and cauliflower, using Bear Creek’s castings mixed into his own in-house “nurseryman blend”. After receiving customer compliments on his fall vegetables, he plans on planting his warm weather vegetables (i.e. peppers, tomatoes, squash and cucumbers) with earthworm castings. Another benefit Cunningham noted was he “…didn’t have to use any fungicides because we didn’t get any fungus on them. Normally I have to spray for fungus but not this time.”
Cunningham refers to earthworm castings as his nursery’s “insurance policy” by saying: “The quicker you get the roots going, the less likely you are to have problems.” His goal for Country Gardens Nursery is “to do all vegetables and herbs in the spring of ’05 [with castings] because in the first trials using the castings, the plants displayed thicker, heavier stems, looked better, were healthier, and will be better for my customers. I also believe they will be better for customers who want to plant their own vegetable gardens.”
Because of Bear Creek Worm Farm’s rare combination of high quality and large supply, Brantley has sold castings to customers in New England and has entertained inquires as far away as California. With shipping costs as high as they are, when asked why customers order from so far away, he replied, “…knowledgeable customers want pure castings that are high in microbial activity and in nutritional content from someone who can guarantee a large, long-term supply.”
Jack Brantley can be contacted at (912) 384-4743; Mike Cunningham can be contacted at (770) 251-2673 Jason Governo, state composting specialist, works with the Engineering Outreach Service within the Biological & Agricultural Engineering Department at the University of Georgia. He specializes in compost business start-up, feasibility and vermiculture. Britt Faucette is an Ecologist and the Research and Development Director for Filtrexx International. He recently received his doctorate degree from the University of Georgia, where he also worked with the Engineering Outreach Service.

Sign up