When added to your soil, the micro-organisms go to work on the organic matter, causing a release of nitrogen, phosphorous and other plant nutrients. Carbon dioxide and a number of organic acids released from the undecomposed part of the humus help dissolve minerals in the soil, providing even more nutrients.
Thus, your soil is best served by having a constant supply of compost-humus in it. The results are not hard to notice. Your plants are healthier and stronger. If the micro-organisms are present in great numbers, they actually prevent fungi and other organisms that are harmful to your plants from getting a foothold in your soil.
In addition, humus lends texture to soil, allowing excess moisture to drain through while still retaining enough of it to provide for the plants' needs.
As as experiment, spread some compost on a patch of hard, compacted soil. Put some water on, not a whole lot, and wait a week. Then put a shovel in it. You'll find that the compost has actually softened up the hard top layer of the soil, making it much easier to dig into and turn over. The more you apply and the longer you keep it there, the more it works on the soil surface to break it up into a crumbly, easily-worked form. Such treatment is what underlies some of the well-known "no-work, no-dig" approaches to gardening.
Dig it in; the better the mix, the better the results. Once down in the soil, the micro-organisms go to work and the soil becomes something different, a more productive medium for your plants.
Compare the soil of a well-composted farm or garden with that to which chemical fertilizers have been added to produce crops and you will understand why farmers in this county are losing tons of topsoil each year. Chemically-treated soil has no body, no tilth, as they say in the gardening books, nothing to hold it down when the wind blows. It requires more and more chemical fertilizer for the same level of production. And, like a State Department explanation, it won't hold water. Such a comparison is the best demonstration of why you want compost in your soil, in ever-increasing amounts.
Next issue: How to make compost.
Copyright Mendocino Environmental Center 2002
Permission granted to excerpt or use this article if source is cited