Composting is a way of integrating your household more fully into natural cycles.  When we compost we are not only reducing the amount of waste that ends up in a landfill, we are helping to create healthy soils.  If you grow ornamental or food plants, adding compost to the soil replenishes a very essential component – soil organic matter.  This organic matter, or humus, provides a steady supply of available nutrients for growing plants and also improves the structure of the soil so adequate amounts of air and water can be present.

The important thing to remember about composting is that what we want to do is provide is an ideal environment for bacteria to decompose raw organic matter.  The bacteria take in nutrients from the compostable materials and then release them slowly into the soil in forms that the plant roots can absorb. And the kind of bacteria that do this best need pretty much the same things we need in order to keep our bodies going – the right amounts of air, water, and nutrients.  

The nutrients we need to pay the most attention to when making compost are carbon and nitrogen.  This isn’t as complicated as it may sound as everything organic contains carbon (C) and nitrogen (N). But the important thing is to provide these elements in the ideal proportions for the bacteria to grow.  Basically, 20 to 30 parts carbon to 1 part nitrogen is the ratio we want to achieve.  So in building the compost pile, a good way to achieve this ratio is to alternate layers of brown, dry materials such as straw or dead leaves, which a have a C/N of about 50 or higher, with layers of green, moist materials such as fresh grass cuttings or kitchen scraps, which have a C/N ratio of around 10.  Raw chicken, horse, or cow manure is also an excellent source of a high N material if you can get a hold of some.  The dry material provides spaces for air and water to be present, the other important aspects of composting to pay attention to.

The compost pile also needs to have sufficient volume so that the heat generated by the biological activity of the bacteria can build up and be sustained.  Good compost piles will reach temperatures of around 120 degrees F, which is hot enough to kill weed seeds and plant pathogens.  To achieve this, the pile should be at least a cubic yard in size (3 ft X 3 ft X 3 ft).  

Maintaining adequate moisture and air space is also very important for getting the compost pile to heat up.  Watering the pile from time to time so that the material appears wet, but not soaked, and turning the pile with a pitchfork every other day or so after it starts to heat will achieve these ends. If the pile does not heat up, it means one of the factors – water, air, or C/N ratio is not ideal.  Tinkering with these factors is fun and will teach you a lot about composting.

As the pile heats, its volume will be reduced, and after a period of a couple weeks, depending on the degree of heating, what was once dead organic matter is now rich humus that will make your soil and plants very happy.  

Text by John Burket