Composting turns garden and kitchen waste into humus. Humus is Nature’s best fertilizer and soil conditioner. The process of decomposition that we call composting happens in nature as billions of microorganisms feed, grow, reproduce, and die as they recycle kitchen and garden waste.
Compost will happen gradually over time. Set a pile of leaves or grass clippings in the corner of the yard and come back in a year: compost, perhaps humus. When you build a compost pile or use a commercial bin, you can speed things up. What Mother Nature will do on her own in a year’s time you can help her do more quickly.
Compost is partially decomposed organic matter. Humus is fully decomposed compost. Humus is the composter’s objective.
There are three types of composting: cold, slow, or passive composting; hot, fast, or active composting; and sheet compositing.
Sheet composting simply involves spreading undecomposed organic materials over the soil’s surface, then working them into the soil to decompose.
Cold, slow, or passive composting involves piling organic matter into a heap and letting Nature takes its course. Little or no turning is involved and composting will occur in time. In cool temperatures, passive composting can take more than a year.
Hot, fast, or active composting requires that the compost pile be turned or aerated and that some attention be paid to the ratio of high-carbon materials–such as dry leaves, straw or steer manure–and high-nitrogen materials–such as fresh grass clippings, green prunings, and kitchen peelings. (An ideal ratio of carbon to nitrogen for hot composting is about 25:1.)
To speed along the work of your compost pile follow these suggestions:
• Set a foundation of plant debris (leaves, weeds, or grass clippings) 6 to 8 inches deep on the ground or in the bin. Add a 1 to 2-inch layer of soil, fresh cow or horse manure, or a few handfuls of blood meal, and then lay the first layer of ingredients for composting.
• Mix “brown” ingredients–such as straw and dry leaves–with “green” ingredients–such as grass clipping and kitchen waste.
• Chop or grind large materials such as plant stems into small pieces. Mix coarse material with finer material such as grass clippings.
• Keep the compost pile moist, but not wet. Compost should never be wetter than a squeezed-out sponge. Cover the pile with a plastic sheet or tarp during heavy rainfall.
• Turn the pile every 3 to 4 weeks to introduce oxygen into the pile and allow the contents to decompose evenly. (This will also discourage odor and flies.)
• Add a 1 to 2-inch layer of nitrogen-rich topsoil (rich in microorganisms and earthworms) or fresh manure or blood meal between each deeper layer of “brown” or “green” ingredients. This will speed decomposition.
• For significant decomposition to occur within the compost pile the heat within the pile must reach 140º to 150ºF. For this to happen, the air temperature surrounding the compost heap must be greater than 50ºF.