NCSU Vermiculture Conference Topic: Earthworm Biology and Environmental Parameters of Importance
Speaker: Dr. John Biernbaum, Michigan State University Dept. of Horticulture where they have a year-round student run organic farm and CSA.
Here are notes of things that I learned and took away:
John’s done specific work on worm composting in unheated structures (more challenging than in heated facilities). This is particularly challenging in Michigan.
Another focus — maximum production per acre
His focus is on creating compost as a resource (not so much focus on the waste management end)
There are 6000 species of worms and only 6 are used in composting — the main one being eisenia fetida (the red worm, red wiggler worm, manure worm)
Worm biology – worms don’t have teeth so depend on other organisms in the soil to break things down. Also worms don’t have lungs so there needs to be moisture so they can absorb oxygen through their skin.
With bigger beds, they’ve moved to pre-composting the worm’s food for efficiency, as opposed to burying food in the bins.
Reproduction — worms are hermaphrodites but do mate, then they lay cocoons. They may start to mate at 60 – 90 days depending on conditions and can create 2-3 cocoons a week. Cocoons take 4-6 weeks to hatch. Worms can live 3-4 years in an ideal system. Rates of reproduction depend on conditions and limitations of the system.
We were asked to raise our hands to indicate our experience by the number of years we’ve been worm composting and the number of square feet of surface area that we operate.
Population density measurement — he started out managing horse manure composting and can see that cubic feet is a measure for some systems like windrows. Square foot of surface area is also common — 2-3 pounds per square foot would be considered high population.
Moisture measurement – % moisture content (wet weight – dry weight)/wet weight. 70-90% is a target range, but not if there is too much food in the bin. If you aren’t weighing the bedding, do the squeeze test. If you squeeze a handful and it falls apart — it is below 40% — too low. Ok is if you squeeze it and it stays in a ball when you open your hand (60%) Ideal is to squeeze it and a couple drops of water come out.
Oxygen – temperature is a factor, as temperature increases, oxygen solubility in water decreases. Also avoid closed containers.
Food – Carbon, Nitrogen, Minerals. In a feeding systems they need to be balanced. There are lookup tables showing makeup of inputs and available minerals.
If you have 100 pounds of worms and are giving 50 pounds of food — consider moisture content of the food to know how much you’re actually feeding.
Feeding trial: Horse manure .5 of weight per day was lowest – 1 of weight per day was mid, plate scrapings were highest.
Temperature. Range is between 40 degrees F to 85 degrees F. Optimum is around 77 degrees.
pH: affects nutrient availability for worms and plants. Note: ammonia gas becomes toxic in a high pH system.
Soluble salts: impacts moisture availability. They accumulate in a system over time and will stress the worms. Not a problem in a flow through system.
Bulk density — impacts oxygen transfer — indicates if there is too much soil which results in migration.
Conclusion — quantifying can take away guesswork in worm composting.
The reference text sold at the conference, Vermiculture Technology: Earthworms, Organic Wastes, and Environmental Management, is available on Amazon.com in hardcover and for Kindle.