Soil test results indicate that approximately 40 to 60 percent of the cropland in Tennessee is too acidic for optimum crop production. Because of this, determining the need for lime by soil testing should be the first step in developing a sound crop fertilization program. Lime neutralizes excess soil acids and increases soil pH which is a measure of soil acidity. Levels of extractable aluminum (Al) and manganese (Mn) are reduced to a nontoxic range as soil pH increases. If not limed as needed, soils continue to become more acidic, reducing the potential for production of healthy plants and profitable yields. The need for lime and the optimum soil pH depends upon the type of crop to be produced.