The Alchemy of Composting

Creating Soil fertility through composting

This installation of the practical blog is about Composting for Maintaining Soil Fertility.

Composting is ultimately a process that involves Alchemy. There are many methods and recipes out there, some of which you may already be familiar with. At the highest level, success with any of these methods is a result of keeping in balance the 4 traditional elements:

* Fire

* Air

* Water

* Earth/Rock

The 4th element, although commonly referred to as Earth, I prefer to think of as Rock. This is to keep in mind that we are not speaking about the entire Planet Earth in this case, just the densest, coarsest, most solid material found on her surface: Rock. Weathered rock is the parent material for all soils, but to form good fertile soil, the elements of Water and Air are needed and Fire to spark biological activity. Let's see how each Earth Element is represented in the compost pile:

Rock - the densest material is represented by brown, fully matured carbonaceous plant matter. Usually, when composting, it is found in the form of straw, but anything that has hardened and is biodegradable can potentially be used: fallen leaves, twigs and branches, wood shavings, animal bones. Carbon materials give a compost pile its' substance.

Fire - the element of lowest density, is represented by green, supple plants containing high percentages of nitrogen. Nitrogen is what sparks biological life and plant growth in our gardens. Nitrogen sparks microbe activity in the compost pile. Although represented by lush vegetative growth, any plant matter that has been cut while green, even if allowed to dry, can be used as a fire element: hay, grass, clippings, tomato and potato vines, green leaves, table scraps. Similarly, animal manures are also high in nitrogen and both fresh and dry manure can be added to compost piles.

Water - is represented by the water we deliberately add to our compost pile, by rain we allow to fall onto a pile, as well as by the moisture contained in the plant and animal materials that we build our piles with. Too much water creates an anaerobic condition. In general, soggy anaerobic conditions can produce harmful bacteria and should be avoided. Not enough moisture and the composting process stops, too much Air.

Air - is represented by the open spaces within a compost pile. Certain materials, such as branches, are very effective at keeping air pockets within a pile, while other materials, such as grass clippings, tend to mat down and resist air infiltration. In general, it is more important to ensure that Air has access to the bottom and center of the pile, than it is to the top and sides of one.

Keeping a proper Air to Water ratio is one important key to composting success. Good, loose, friable garden soil can be used as an example. This good garden soil contains ~50% pore space. Ideally, this pore space is half-filled with water and half left open to air. Of course, in practice, the water content in both soils and compost piles, is constantly fluctuating between one extreme and the other. Our job as Gardeners is to keep this 50/50 Air to Water ratio as best as we can (with some adjustments, in certain situations). Compost piles should be managed with the same goal in mind: keep that 50/50 balance as best as we can, over time.

The other balance to keep in mind when composting is that of Rock and Fire, that represented by carbon and nitrogen. In general, if carbonaceous materials and nitrogenous materials, as defined above, are added in equal parts, by volume, again a 50/50 ratio, by volume, this will keep an effective Carbon to Nitrogen in balance in the pile. This 50/50 ratio of Rock to Fire is more difficult to achieve than that of Air to Water, because there is much more variability in these carbon and nitrogen materials. However, the truth is, that as long as the Air to Water ratio is kept fairly well-balanced, the microbial life in the pile will transform almost any combination of carbon to nitrogen materials into finished usable compost within one year's time in most locations. So, please do not be hesitant to start composting by what may seem to be, at first, an overly complex process. The microbial life within the compost pile will find the food combinations that they need. The only question is one of efficiency, and that we can improve through practice. Speaking of microbial life, this brings us to a final analogy.

The compost pile can be seen as one large stomach, a giant digester. When we build a pile, we are feeding the microbial life in that pile, the 'bioherd'. This microbial life prefers a balanced diet, just as our own bodies do. Nitrogenous materials (Fire) are analogous to us living on a diet of fruit and salad vegetables. Fruit, especially, gives us quick energy to get going, but does not sustain our activities over time. Carbonaceous materials (Rock) are analogous to a diet of grains and root vegetables. Grains give us energy for the long haul, but without some Fire accompanying our meal, these foods can leave us feeling too heavy to get started. Likely, I believe , that we have all gotten by on an imbalanced diet for a time, until learning better habits from the experience. Both kinds of energy, fast and slow, are necessary for our bodies and for the body of the compost pile.

Next blog, we will continue by describing how we actually apply the principles presented today to the building of compost piles here at Living Earth Garden Project.