Rotting watermelons, pig manure, fish guts, weeds, low grade paper, spoiled oysters, decomposing lettuce, leaves from oaks, maples, and other trees, worn out wool sweaters, even old cotton underwear - these are just some of the ingredients we use to make the compost which is critical to our success in growing fruits and vegetables.
Anything that was once alive can be composted. Compost results when biological processes break down once-living materials and reform their components into humus which can nourish successive generations of living organisms. Humus is the nearly magical substance which brings life to soils.
Composting is the Earth's digestive process. In the presence of air and water, the beneficial decomposers (that is the bacteria, fungi and molds which are everywhere in our environment) begin to multiply, feasting on materials only slightly different from what we eat. After the feast, they leave behind a rich, dark, soil-like material that is full of living things and has an earthy fragrance which speaks to ancient memories of bountiful harvests.
This decomposition into fertile soil happens anywhere organic matter accumulates. A few leaves blown onto barren rock or the corner of a parking lot decay to begin the process of soil creation, perhaps supporting moss or lichen. Unhindered, this process will continue, year after year, nurturing successively larger organisms, which leave behind more waste to decay into soil. In this way, life inhabited the young Earth and now reclaims barren and abused sites.
Although the nature of life on Earth favors decomposition wherever organic matter accumulates, there are some advantages to making compost in larger quantities. A cube of materials about three feet on a side can heat up to 150 degrees due to the action of certain bacteria. At that temperature, decomposition proceeds faster so that insects, weed seeds and diseases are killed. Although many piles never heat up, they can still produce great compost. The rich soil of the forest shows that even without human intervention, leaves, sticks and the wastes of small animals become good humus.
Compost is alive. It contains billions of organisms per teaspoonful, ready to work on mineral particles and organic matter, to digest them and release their goodness. Other organisms in compost collect sunlight, while they capture and process nitrogen. Besides the life it brings to soil, compost is valuable for the structural changes it creates. It aerates clay soils and helps sandy soils retain water. Humus is like a sponge, storing rainfall for slow release to plant roots. Because of its electro-chemical nature, it also holds nutrients. The beneficial organisms in compost are so numerous that they suppress harmful organisms. Some composts are even being used to control soil-borne diseases.
Although the rotting watermelons and other smelly ingredients of our compost all turn to a valuable, fragrant resource in a matter of months, the non-biodegradable debris of our society - chip bags, fast food packaging, plastic, aluminum and glass containers that slip in with a batch of leaves or food waste - still look pretty much the same, only dirtier. As I pick these items out, I dream of the future where only biodegradable packaging and refillable bottles will be used.
We avoid composting materials which are contaminated with toxic substances such as heavy metals and pesticides which are not easily degraded. However, in controlled situations, the powerful life force of the compost process may be the best way to decompose or neutralize toxic substances.
If you're not composting yet, it's easy to start with leaves this fall. As you participate in one of nature's most important cycles, you'll be producing one of our most essential resources - fertile soil.
This is Bill Duesing, Living on the Earth
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