Lime requirement studies on selected soils

It is recognized that there are important relationships of lime to soil fertility and crop production and that soils differ in related chemical and physical properties. Recommendations for applications of lime in Tennessee are made for both field and horticultural crops on soils of widely differing properties including differences in parent material, texture, humus content, and clay mineral type. At present, state recommendations for applications of lime are made largely on a basis of pH of the surface soil alone without considering texture, organic matter content, or other soil properties. A "rule of thumb" is used to recommend 2 tons of ground limestone per acre for each pH unit increase desired. This system includes a lime factor of about 2, recommending twice the required amount of calcium carbonate to compensate for coarseness, mixing, time required for reaction, and other factors which would limit the completeness of the reaction.

In the future some soils not now used may be needed for agricultural production, or a more intensive management may be required on many soils than is now practiced. Either situation would tend to require a more precise system of making lime recommendations. The present distribution of soil samples may not represent all the soil conditions of the state, or the degree their future use might indicate. Some reports indicate that following present recommendations does not accomplish the pH adjustment desired. Liming recommendations should give some consideration to the subsurface layers of soils within the rooting depths of commonly grown crops.

These possibilities coupled with the considerable differences among soils indicate the desirability of a study of the surface and subsurface layers of certain differing soils with respect to characteristics affecting lime relationships.