Basics of Composting

I subject I was thinking about as I cleared weeds and roots out of old raised garden beds, and set up a new garden bed. Backwoods Magazine has a story the covers the basics of composting:

It's the action of those unthanked microbes that are responsible for successful composting. Microbes break down larger things — banana peels, cow manure, ageing lettuce — while digesting them. This digestion process results in the release of elements in a form that plants can use. That's why rot is such a critical component of the natural cycle. Animal and vegetable materials all contain critical nutrients, but not in a form usable to plants. But if the material is decomposed and mixed with soil, then the nutrients are released into a form plants can use.

But microbes can't work in a vacuum. They need certain conditions in order to survive and do their job. Specifically they need four things: 

• Energy (in the form of carbon). Microbial carbon is supplied through whatever dry, bulky vegetative waste you have on hand: leaves, straw, cornstalks, even sawdust. 

• Protein (in the form of nitrogen). Nitrogen (sometimes called an Activator) is what stimulates the microbes, and is found in grass clippings, green vegetation, and such additives as kelp meal or blood meal. (Microbes need much less nitrogen than they do carbon, so don't overdo the protein.) 

• Oxygen. Oxygen merely means that microbes must operate in an aerobic (as opposed to an airless anaerobic) environment. Occasionally turning your compost pile provides this; alternately, the actions of worms and other soil dwellers help aerate the compost as well, though it will take longer. 

• Moisture. Moisture is necessary for rot to happen. In fact, reducing moisture (dehydration) is an ancient form of food preservation, since microbial action requires some moisture in order to work. But too much moisture — a waterlogged compost pile — will slow down microbial action as well, since it contributes to an anaerobic environment. That's why adequate drainage is necessary for compost piles.

The author goes on to explain:

 Ideally, a compost pile consists of a ratio of two parts vegetable matter (leaves, grass, straw) to one part animal matter (manure). The ratio of carbon to nitrogen should be about 30:1, meaning you should have 30 times more dry bulky vegetative waste than nitrogen-rich sources such as grass clippings or sea kelp. 

Materials should be mixed rather than thickly layered; or at least layered thinly. If you pour several cubic yards of grass clippings onto your compost pile, for example, it's likely to compress into a stinky anaerobic sludge. However if you first dry the clippings (or take the green clippings and mix them thoroughly with leaves) before adding them to the compost pile, the materials will break down more efficiently and with less smell. Avoid grass clippings or other materials that have been heavily sprayed with pesticides or herbicides. 

Leaves are particularly useful. Here in north Idaho we're surrounded by almost pure conifers; but for those lucky souls who live in deciduous areas, leaves are one of your greatest assets. Left alone, leaves compost very slowly; but decomposed leaves are one of the best possible natural composts. The richness of eastern gardens grown in "humus" illustrates this. 

So rather than complain about the massive volume of leaves you have to rake each fall, instead layer those leaves into your compost pile and wait for the goodness to come forth. If possible, chop or shred the leaves first. This will reduce matting and speed up the decomposition. Mix the chopped leaves with other stuff and the leaves will decompose about four times faster than if they were simply piled and left alone.