pH AND THE COMPETITIVE ABILITY OF PLANTS
Logically then, rhododendrons and other ericaceous plants (broad-leaved evergreens) thrive in acid soil because their roots can take up the form of nitrogen available to them in acid soil. Such plants also have a high iron requirement; iron is an element which becomes less and less plentiful as alkalinity increases. Here, then, is a key to the competitive ability of various species of plants. We expect to find rhododendrons and azaleas ablaze on acidic granite ridges in the Great Smokies, while clovers thrive on lime-rich soils in the Middle West. We seldom see clover growing well in New England except where farmers have applied lime freely. Thus pH has a way of determining the appearance of our native landscape by favoring one group of plants over another.
Soil pH is a scale of acidity-alkalinity that is neither complex to understand nor difficult to use. Relative acidity affects many aspects of soil use and plant productivity. Make pH tests of separate samples of soil from different parts of your property; do not mix the samples. Use a home "do-it-yourself" test kit if your budget cannot stand the cost of professional testing of numerous samples. Investigate first, however, for your state agricultural station may offer the service free. Armed with test results and the knowledge of pH presented in this chapter, you can manipulate applications of lime, sulfur, organic matter and fertilizer to best advantage so that your soil will favor desirable plant growth.