The soil must be regarded as a living organism. An acid fertilizer, because of its acids, dissolves the cementing material, made up of the dead bodies of soil organisms, which holds the rock particles together in the form of soil crumbs. This compact surface layer of rock particles encourages rain water to run off rather than enter the soil.
For example, a highly soluble fertilizer, such as 5-10-5, goes into solution in the soil water rapidly so that much of it may be leached away into our ground water without benefiting the plants at all. This chemical causes the soil to assume a cement-like hardness. When present in large concentrations, they seep into the subsoil where they interact with the clay to form impervious layers of precipitates called hardpan.
Many artificial chemical fertilizers contain acids, as sulfuric and hydrochloric, which will increase the acidity of the soil. Changes in the soil acidity (pH) are accompanied by the changes in the kinds of organisms which can live in the soil. For this reason, the artificial fertilizer people tell their customers to increase the organic matter content of their soil or use lime to offset the effects of these acids.
There are several ways by which artificial fertilizers reduce aeration of soils. Earthworms, whose numerous borings made the soil more porous, are killed.
The acid fertilizers will also destroy the cementing material which bins rock particles together in crumbs. Chemical fertilizers rob plants of some natural immunity by killing off the micro organisms in the soil.
Many plant diseases have already been considerably checked when antibiotic producing bacteria or fungi thrived around the roots. When plants are supplied with much nitrogen and only a medium amount of phosphate, plants will most easily contract mosaic infections. Host resistance is obtained if there is a small amount of nitrogen and a large supply of phosphate. Fungus and bacterial diseases have been related to high nitrogen fertilization, and lack of trace elements.