Composting

How many of you know that Sierra Vista recycles a greater percentage of its waste stream than any other city in Arizona - 15 percent to be exact? I didn't know that either until I heard Pat Bell of the Sierra Vista Department of Public Works speak at a recent Cochise County Master Gardeners Association meeting where I learned that this remarkable percentage is the result of the city's highly successful composting program. Later at the High Desert Gardening & Landscaping Conference, I had the opportunity to visit the city's composting facility and see first-hand how it operated. I was especially impressed by the scientific rigor with which the composting process is regulated. Ed, the plant supervisor and our guide for the tour, was very knowledgeable about carbon-nitrogen ratios, optimum temperatures, moisture levels, and the like. My curiosity prompted me to see what information I could find about composting on the web. A quick search using the Alta Vista search engine found 20,000 documents containing the word "compost."

A favorite site of mine that turned up in the search is hosted by Cornell University (http://www.cals.cornell.edu/dep/compost/). Here is listed everything you ever wanted to know about composting. One section deals with the scientific and engineering principals involved in the composting process. Another section discusses composting projects that can be used by school teachers in the classroom. And a third section contains extensive lists of references. I found the scientific and engineering discussions to be the most interesting.

One of the biggest problems for composters in Sierra Vista at certain times of the year is finding enough green stuff (nitrogen-rich materials) for the pile. A page at the Cornell site discusses using nitrogen fertilizers for this purpose. It says that organic nitrogen sources (green stuff) decompose slowly, releasing nitrogen at rates comparable to the rate of growth of microorganisms in the compost. Synthetic fertilizers, on the other hand, release nitrogen at very fast rates that exceed the ability of the microorganisms to use it. This is especially true during the colder months when lower temperatures slow down the growth rate of the microorganisms. As a result, more nitrogen is released than can be taken up and the excess is released as ammonia gas.

In order to preclude the formation of ammonia gas (which can be detected with your nose) you should apply nitrogen fertilizers lightly in a series of applications over a period of time. Also, the total amount of fertilizer to be applied is much less than might be expected from its nitrogen content alone, although no research results are available to quantify the rates or amounts.

This site offers something for everyone interested in composting. If you are the engineering type who likes to quantify everything, there are tables of carbon, nitrogen, and moisture values for a wide variety of materials and formulas to determine the optimum mixes of everything going into your compost pile. If, on the other hand, you are a free spirit who uses the pds (pinch, dab, and smidgen) method of constructing your compost pile, you will also find plenty of practical, easy to understand instructions to make your composting experiences even better.