As part of my permaculture design for Rukmapura Park Hotel, I will create community garden plots and build compost bins nearby; I will then use those bins to make and store compost for the gardens. For those that don’t know, compost is a soil amendment created through the controlled decomposition of organic materials such as leaves, twigs, straw, grass clippings, and vegetable food waste.
Compost has four key elements: nitrogen, carbon, water, and air. For nitrogen, add layers of green plants and manure; for carbon add layers of brown materials–such as leaves, straw and mulch; hose down and flip the pile to introduce water and air.
BUILDING THE PILE
The ideal compost pile is 3 foot tall by 3 foot wide; you will build it up by repeatedly layering three materials: brown (carbon), green (nitrogen), and soil. The first, or bottom layer, should be 3 inches of brown materials.
Next, pile on 2 to 6 inches of green. *If your green material is dense and will mat together, the layer should be only 2 inches; this would include things like grass clippings and kitchen scraps. *If the green material is loose, the layer should be 6 inches; this would include things like vines or stems.
The third layer is soil; it provides clay and mineral content as well as microorganisms that enhance decomposition. *If your green layer contains weeds with soil attached to their roots, you can skip this layer. Repeat these three layers until you have a 3×3 foot pile. *The final layer should be brown.
MANAGING THE PILE
The microorganisms–in their breaking down of the materials–will generate heat. For this reason, the pile needs to be kept moist; otherwise it will become so hot that the (beneficial) bacteria responsible for the decomposition will not be able to survive, and the pile will go inert. Make sure the pile is only moist; if you squeeze a handful of material and water comes out, the pile is too wet.
The pile’s beneficial bacteria also need air to survive. For this reason, the pile should be turned over every so often. More precisely, on days 7, 11, and 18. *As you are flipping make sure that the outside layers, get moved into the inside of the pile, as the materials on the inside breakdown faster.
After day 18, the compost can be used as a fertilizer and soil amendment. However, the longer you let it breakdown (continuing to flip) the better the compost becomes. The best compost will have gone through the decomposition process for one to two years.
You will know the health of your pile by its smell: the only smell a healthy compost gives off is that of earth–which is very subtle. However, an unhealthy pile can result in either a strong ammonia or sewage like smell.
The smell of ammonia is an indicator that the pile contains too much nitrogen. The smell of sewage indicates that the pile has gone anaerobic–due to too much moisture or compaction. *Both of these issues can be fixed by flipping the compost into a looser pile and adding layers of straw.
Straw is an excellent choice of brown material; it breaks down nicely, and helps with aeration because it has hollow stems which allow for air flow. *Use it whenever possible.
HOW TO APPLY / HOW MUCH TO USE
Spread the finished product over the top of the soil, mixing it in shallowly-into the top two inches of the soil. (Earthworms and other soil organisms will do the rest). *A generous application of a 1 inch depth is recommended.
At this one inch depth, one cubic foot of compost will cover a garden area of 12 square feet. *To determine how many cubic feet of compost you have, simply calculate the volume of your compost pile. You do this by multiplying height by width by length (assuming your compost container is a cube).
So for example, if your compost bin is 3 feet tall, 3 feet wide, and 4 feet long , it will hold 36 cubic feet of compost. (3 ft x 3 ft x 4 ft = 36 ft). But how many square feet is this? (It depends on the depth).
Since we’ve already established that one cubic foot of compost laid an inch deep will cover 12 square feet, we simply multiply our total cubic feet (36) by 12 to find out how many square feet our compost will cover (when spread in a one inch layer). So: 36 X 12 = 432 square feet.
If your compost bin is a shape other than a cube (such as a cylinder), formulas for determining the volumes of various shapes can be found under the Math tab.