Most soils in the estern part of the United States are naturally too acid for best results with lawns and vegetable and flower gardens. Lime can be applied to reduce soil acidity, but first a soil test to indicate the needed amount is desirable. Application of too much would be harmful and too little would be inadequate.
Residents of the District can have their soil tested for free by D.C. Cooperative Extension Service, Washington Technical Institute (629-4181) and Virginia and Maryland residents can get tests free charge from their state universities. Contact your county extension agent, listed under the county government in the phone book, for information on how to take the samples for testing and where to send them.
The degree of acidity or alkalinity of a soil is designated by the term pH. The pH scale ranges from 0 to 14. At pH 7.0, the acidity increases; pH 6 is slightly acid, pH 5 strongly acid and pH 4 very strongly acid.
Most lawns grasses and vegetable and flower plants do best in very slightly alkaline soils.
One of the best times to apply lime is in the fall as lime is a slow-acting substance because of its insolubility. While dilute acids gradually work on it, they do so at a snail's pace.
Acids work only on the outer surface of lime particles. Thus, the more surface exposed, the faster they work. Fineness of grind is the secret of getting lime to dissolve rapidly. Fineness of grind does not increase solubility; it merely provides more surface.
If the soil is too acid, application of lime furnishes calcium, reduces soil acidity (both the natural acidity as well as that created by most fertilizers), favors root growth, reduces winter killing, encourages legume bacteria to fix more nitrogen from the air and promotes better soil granulation.
Acidity and liming have important effects on the solubility, availability and sometimes the toxicity of a number of elements. As acidity increases, the solubility of aluminium, cooper, iron, manganese, and zinc also increases. Sometimes toxic concentrations of these elements may occur in highly acid soils.
Rainfall percolates through the soil and leaches (washes) lime out in the drainage water or below the reach of plant roots (soils in the East are more acid because of greater rainfall); harvested crops remove lime from the soil; and erosion may wash away as much as 50 pounds of lime from each acre every year.