What Makes Compost?
Worms, Bugs and Shrews in your Pile.
Your compost pile is a beautiful dance of organisms, ranging from the very small bacteria and fungi to the bigger slugs, worms and frogs. As the conditions in the pile change from cool to warm, from new material to nearly decomposed material, from wet to dry, the various players shift to favor the ones who are most efficient under the current conditions. The pile becomes a mini-ecosystem, each team member relying on the other ones.
In this second part of our series "What Makes Compost?", we will look at the "Team Compost" players which you can see most easily--the macroorganisms.
The macroorganisms are the players we notice the most.
Worms, in particular, are welcomed by gardeners as a sign of healthy soil and a good compost pile. In fact, in the world of decomposition, there is a subset called vermiculture based on these guys alone.
Worms are only one of the many, many kinds of macroorganisms, and again, in healthy pile they are abundant. One teaspoon of compost can contain 30-300 nematodes. In a square yard of woodland soil, you may find 30 million nematodes, and 250 species of mites. As general categories, macroorganisms are grouped as earthworms, bugs, nematodes and larger creatures.
Macroorganisms help decomposition in a physical way. While the microorganisms used chemicals to break down the vegetable matter, macroorganisms chomp and grind the organic matter into smaller bits, as well as eat other organisms to keep the populations fresh.
Earthworms are such friends to decomposition that entire books have been written about them alone. Earthworms are to the macroorganisms what bacteria is to the microorganisms. They are the stars.
When earthworms eat, the organic matter is broken up and digested by hormones, enzymes, and other fermenting substances. In the gizzard, the matter is finely ground. At the back end, the digested vegetable matter is released as casts, one of the most highly prized compost substances for organic gardeners. Casts have a high bacteria count, organic material, nitrogen, calcium, magnesium, phosphorus, and potassium. On top of this, a worm can produce its own weight in castings each day.
Besides providing us with Compost Gold (casts), the earthworms don't laze around eating their fill. While eating, they work--churning and turning the pile as they slither through it. Earthworms play a significant role in mixing soil.
Earthworms work closely with bacteria in decomposition. Worms digest for bacteria and bacteria digest for worms. Then in the end, the worms eat the bacteria, and the whole cycle continues.
Insects and Bugs
Insects include all bug-like creatures (I'm not being scientific with the use of this word) including millipedes, centipedes, sow bugs, springtails, beetles, ants, flies (and their dear little cherubs: maggots), spiders, mites and I'm sure there are more. All these small crawly things help break your grapefruit rind into something your roses can use. Some of these digest the organic matter while others play a role in digesting other bugs. In either case, they are integral to a healthy compost community.
Nematodes are a type of tiny worm averaging less than 1/8" (2mm) long. If you seem them, they usually look like moving human hairs. They are the second most dominant form of life, with maybe as many as 1 million species world wide. Many gardeners think of them as parasites that damage the roots of their plants, yet this only part of the picture.
Nematodes can be divided into 3 groups: those that eat decaying organic matter, those that are predators to other nematodes, bacteria, algae, protozoa, etc, and those that are garden pests attacking plant roots.
Obviously, you don't want your plant roots eaten, but of the other two groups, nematodes play an important role in the pile. Next time you hear the word "nematode", make sure you're not being specie-est in your prejudices!
With the abundance of bacteria, worms, insects and fungi, it is inevitable that larger creature come to join the banquet. Frogs, snail, slugs, shrews, and others eventually join in the performance.
Compost piles are like a Russian novel--a complex play of many actors, events and themes, all acting both randomly and in harmony. When you observe your pile, it is quite nice to stop and marvel about how well it works. The tricky part is managing this chaos. It's a bit like herding cats.