On Evaluating Crop Response to Lime in the Tennessee Valley Region

Excessive soil acidity has long been recognized as one reason soils become unproductive, and liming to neutralize excess acidity has been practiced at least since the second century B.C. [5, p. 125]. Although liming has become a common practice, some researchers contend that farmers use too little lime [e.g., 5, p. 125]. Although lime is sometimes used to supply calcium or magnesium, it is principally used to neutralize soil acidity [3, p. 178], commonly measured by soil pH. Many agronomists agree that most crops require some lime if pH falls below 5.0 and that most require no lime if pH is 7.0 or higher [17, pp. 221–222]. When legumes supplied nitrogen for other crops in rotation, most lime recommendations were designed to raise soil pH to 6.5 or higher to accommodate the legumes. Now, however, nitrogen requirements for most crops are supplied from fertilizer, and some lime recommendations aim for pH levels somewhat below 6.5, at least for non-legumes such as corn and cotton.