Monday, July 21, 2014

Compost: A Primer

My compost bins when I arrived at our new place.
Compost is a gardener and farmers gold, and is probably one of the best things we can do for our planet much less our soil. Yet, for many gardeners it remains something of a mystery. The questions I often hear are: How do I make it? How do I use it? What exactly is so great about it? What can I compost? Here’s a quick primer to get folks started on making their own and putting it to good use. 

What is compost?

Compost is essentially a crumbly black soil-like material that results when organic matter (leaves, food waste, fish bones, coffee grounds and the filters, grass clippings, etc.) is broken down by assorted organisms living in the soil. The process tends to be rather slow, but like many good things, it is worth the wait. A teaspoon of compost, according to Lowenfels and Lewis in their classic, Teaming with Microbes, contains “up to a billion bacteria, 400 to 900 feet (150 to 300 meters) of fungal hyphae, 10,000 to 50,000 protozoa, and 30 to 300 nematodes.” While that might sound a little scary, it shouldn’t. Healthy soil is very much alive with all sorts of things that quietly go about their business, literally and figuratively creating the foundation for our lives. Compost also comes with other critters like worms as well as the assorted minerals and nutrients plants need to lead healthy, robust lives. (Here when I say plants I don’t just mean vegetables, but I’m also talking about trees, grass, flowers, shrubs, and herbs to name but a few.) It is a life-giving substance that teems with life itself. It is easily the best thing a grower at any scale can give to their soil and plants.

What to compost?

Technically, any organic material can be composted. This includes coffee filters, newspaper, cardboard, kitchen scraps, tea bags, paper plates, grass clippings, garden waste, and fish bits and bones. Old cotton and wool rugs and t-shirts, too, have found their way to my bin with good effect; however, it is worth noting that these were bins set in the soil. Certainly, there are those who would have a longer and a shorter list than that, but for my purposes these items work well. I do make certain exceptions at different times, such as using garden waste and grass clippings as mulch, but that is just another form of composting in a different place.

There is a great deal of talk about C:N (Carbon to Nitrogen) ratios in a compost pile that can seem intimidating to beginners. Carbon comes in the form of leaves, woody stems, momigara (rice hulls), soba hulls, straw, as well as newspaper and cardboard. This keeps the engines running, so to speak, of the decomposers in the soil. Just like runners before a race, the decomposers use the carbon in the soil to keep their energy levels steady. Nitrogen goes in as fresh grass clippings, kitchen waste, and urine. It helps the decomposers make the enzymes and proteins that let them process the organic matter.

If there is too much carbon, the microbes use up all the nitrogen and can’t produce the enzymes and proteins to break down the carbon. The breakdown process will slow down until the balance is restored. Too much nitrogen, and the microbes will focus on eating it and leave the carbon for later. A balance then, is needed to keep the system running.

Composting is an art as much as a science, so being overly fussy about how much of what goes in isn’t necessary unless the gardener wants it to be. Lowenfels and Lewis among others offer excellent advice on tailoring compost for specific purposes, such as trees versus vegetables versus grass, which is worth knowing but doesn’t have to be strictly followed. Gardeners should simply begin and see what happens.

Next: How to make compost

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