To support the life of growing things over a prolonged period of time, all soil will inevitably need to be enriched in some way. Plants use up many of the nutrients within it, and others are leached away as water passes through. The vegetables, herbs, and flowers that we grow can obtain the carbon, hydrogen and oxygen that they need from air and water. Any complete commercial fertilizer can provide the three other nutrients that they primarily use: nitrogen, phosphorus, and potassium. Relying solely upon fertilizers, however, can eventually result in soil that is stripped of many other health-giving ingredients. They cannot correct or improve soil structure, for example; this requires the addition of organic matter. Also, fertilizers cannot compensate for unbalanced soil pH.
Humus, the end result of composting, can sustain a garden just as well as fertilizers in the short term while also bringing with it such beneficial things as microbes, enzymes, and earthworms. Composted materials also improve the soil structure, providing it with aeration and allowing for greater moisture retention. Introducing composted soil into our gardens over time can adjust the pH and bring it into proper balance. Because it does not carry nutrients in concentrated form, there is no danger that the surface feeder roots of our plants will be burned when we apply it. Humus is, in short, the most natural and complete substance that is available to us for replenishing the soil in our gardens.
Unfortunately, a stretch of time is required before we are able to obtain it: as much as a year, or 6 or 7 months from early autumn until spring at the least. If we intend to use composted soil in our gardens then we have to plan ahead and begin setting out our organic materials to decompose long before the growing season begins. Frequent turning and moistening can speed up this process, as can the introduction of earthworms. Still, the period of time can be longer than the eager gardener is willing to wait through.
One compromise that works well for many gardeners is to use fertilizer to “jump start” the garden soil and then use composted soil to sustain it over the long haul. Most soil will benefit from a complete fertilizer – that is, one that contains nitrogen, phosphorus, and potassium all in balanced proportion. This should be mixed into the soil, and watered in, before any planting is done. Our gardens will then have the basic nutrients that they need to thrive; and in the meantime, we can allow nature to do its work in the compost. Once the compost is ready to be drawn from, we can begin to rely upon it more and more until, finally, it is supplying everything we need to sustain our gardens – in a never-ending cycle.