Originally Published In The Deseret News -- Wednesday, November 8, 1995
`Recycling' Pile Is Worth Effort. Elements Include Organic Matter, Oxygen And Carbon-nitrogen Ratio.
Larry Sagers Is A Horticulturalist With The Utah State University Extension Service.
I am frequently asked by gardeners how they can make gardening more enjoyable and more productive. The easiest and most concise answer is to improve the soil. Nothing is more difficult or limits productivity as much as poor-quality, unworkable soil. This week I will explain the general composting process, and next week I will cover specific materials and how to compost them.
Fall is the most important time of the year for soil improvement. One excellent, abundant and inexpensive soil-improvement material is now free for the hauling. This abundant resource is, of course, the fallen leaves that now blanket the city. Most gardeners covet the deep, rich, black soil that they often see as they hike in forested areas. The soil got that way because every year the leaves fall underneath the trees and are never removed. Trees actually grow best in materials they recycle themselves year after year.
Composting replicates this system of breaking down organic matter on the forest floor or prairie grassland. Nature recycles everything - twigs, fruits, cones, leaves and plants, along with animal waste and the animals themselves into a nutrient rich humus that feeds the plants and allows them to flourish.
Occasionally, I hear protests from gardeners who consider composting to be too much of a problem. Yet, the benefits to the soil are so great that serious gardeners will never protest. A little technical data help gardeners understand the process and will make their efforts more successful.
The carbon-nitrogen ratio is the basis for successful composting. The ideal ratio of raw material is between 25 and 30 parts carbon to one part nitrogen by weight. It is difficult for home gardeners to achieve this ratio scientifically. Achieving a proper mix is usually a matter of trial and error. A good rule is that green materials are high in nitrogen while woody materials are high in carbon.
In excess of 95 percent of the raw material being composted is carbon, hydrogen and oxygen from plant photosynthesis. Sugars from photosynthesis are converted to all kinds of plant products. Decomposition changes the plant components back to basic raw materials. High carbon materials do not decompose without adequate nitrogen in relationship to carbon. Too much carbon results in a pile that decomposes slowly because the microorganisms require nitrogen to synthesize proteins in their own bodies. Without nitrogen, they reproduce very slowly. Decomposition occurs from the feeding of these microorganisms. Consequently, the faster they reproduce, the faster the compost is formed.
Microorganisms that break down the material chemically include many types of bacteria, fungi and actinomycetes. In addition to the microorganisms, there are larger invertebrates that break down the material physically. These include earthworms, centipedes, mites, nematodes, certain beetles, sow bugs and symphylams, earwigs and even slugs and snails.
A well-maintained compost pile has a moisture content of 40 percent to 60 percent. Since most gardeners lack sophisticated moisture meters they depend on the ones at the ends of their arms. Pick a handful of compost and squeeze it tightly. If water runs out, the pile is too moist, if the material feels dry, it needs additional water. The proper moisture content usually feels similar to a sponge that has been soaked and wrung out so it is damp.
Composting also requires oxygen. Decomposition occurs from organisms feeding on plant material. This respiration process requires oxygen. Without it, the air is used up and anaerobic bacterial take over decomposition. Although it still occurs, it is very slow.
A successful compost pile requires adequate material. The minimum size pile is at least three feet in each direction. Smaller amounts do not heat and decompose well. Piles that are too large also exclude air near the center. Generally, home compost operations should be limited to piles that are approximately 5 feet in each direction. Gardeners who do not want to deal with compost piles should consider sheet composting. This involves spreading a layer of organic matter over the entire garden area and tilling it in. Add nitrogen fertilizer to stimulate the microorganisms to grow and break down the organic materials.
© 1998 Deseret News Publishing Co.