These three points are chiefly important now, at the beginning of
our discussion on converting a native soil into Gardener's Loam. They will lose their importance once we have incorporated soil amendments and extra organic matter into the soil, for then original type will be so modified that it will have to be revaluated in light of its new characteristics.
An accurate test of texture and type requires an involved laboratory procedure. A rough check, accurate enough for gardening purposes, can be made by the soil wash test, as described in the chapter on testing (Chapter Three).
A CULTURE OF MICROORGANISMS
"I certainly don't want to add germs to my soil," exclaimed one gardener when I tried to persuade him to treat peas and beans with a nitrogen-bacteria culture. He would have been astounded if he could have seen the billions upon billions of microorganisms he harbored in his relatively poor soil. He just could not accept the idea that soil is a culture of such organisms, just as much as it is a mechanical support for plant roots.
Few gardeners deliberately set out to increase the biological life of soil, yet this is the main purpose behind every addition of organic matter. (Long before he knew why, man observed that plants grew best around places where rotting plants and manure had accumulated.) When we treat soils so that beneficial bacteria and useful fungi are stimulated, plants grow better and returns for time, effort and money used are increased. Much of this benefit concerns plants that prefer near-alkaline soils. Acid-soil species, however, are also benefited by the stimulation of useful fungi. A good example of this are the mycorrhizae-specialized fungi that form a feltlike covering on roots of acid soil plants and help them use ammonia as a source of nitrogen. Without these fungi operating in the soil, rhododendrons, azaleas, blueberries, hollies and many other ericaceous plants grow poorly, if at all. When we provide conditions that favor rapid increase and continued growth of mycorrhizae, these plants thrive. If, however, plants are set in heavy clay or planted so deeply that air does not move freely around the roots; or when soil moisture fluctuates widely (sometimes wet and sometimes dry), or when a
protective mulch is missing, both plant and fungi suffer. I have several times made the statement, "To a considerable extent, the culture of acid-soil plants is the culture of mycorrhizae. Do what is good for the fungi and the plants will thrive." The same might be said for plants that thrive in less acid soils as well.