Fall Lime Report is Now Available

Soil acidity is one of the biggest soil factors affecting plant growth and ultimately crop yield and profitability. Most soils in Kentucky are naturally acidic so periodic applications of lime are needed to neutralize acidity and maintain crop productivity. Lime quality can vary widely depending on the chemical properties of the stone and the particle size.

Materials commonly used as lime are either ground-up limestone rock, ground-up marl or products of limestone which have been altered by burning to make them more water soluble than the ground-up rock itself. By far the most common liming material in Kentucky is ground limestone (aglime), most of which is calcium carbonate.  In some instances, there is enough magnesium carbonate present for the lime to be termed “dolomitic.”

When applied to soil, the liming material reacts with soil moisture to release particles of calcium or, in the case of dolomitic lime, magnesium. The rate at which the lime material dissolves to release these particles is largely controlled by how finely it is ground and the chemical form of the material (carbonate, oxide or hydroxide). The finer the material, the more rapidly it dissolves. Oxides (burned lime) and hydroxides (hydrated lime) are more soluble in water and react much more quickly than carbonate forms of lime (calcitic aglime or dolomitic aglime).

Calcium or magnesium particles are attracted to and are held by clay particles in soils after the liming material dissolves. This neutralizes soil acidity, increasing soil pH readings. It also means that lime does not move very fast downward through soil. For this reason, lime can be applied when-ever practical, although it should be applied far enough before planting to allow time for adequately reacting with the soil and neutralizing acidity, ideally during the fall.

Even when ag lime is applied according to soil test recommendations, the actual adjustment in soil pH is not always predictable, because the quality of Kentucky ag lime varies among quarries and over time.  Because of this, the Kentucky Department of Agriculture collects samples and tests the quality of lime from quarries around the state and then provides the University of Kentucky with the data.  UK then publishes the lime report in spring and fall.  Just this past Friday, the fall lime report was released with current RNV’s (Relative Neutralizing Value) for lime in Kentucky. 

The University of Kentucky makes lime recommendations based on a 100% effective lime (100% RNV).  Because ag lime is 100% effective, the bulk lime rate required needs to be determined for each available lime source based on the RNV.  Once you have the RNV, you can determine how much bulk lime will be needed with this simple formula: Bulk Lime Rate=100% Effective Lime Rate/(RNV X 100).

The 2014 Fall Lime Report can be found online at http://soils.rs.uky.edu/technical_Info/.  For more information on lime and nutrient recommendations, contact the McLean County Extension Office  at (270)273-3690.   Educational programs of the Cooperative Extension Service serve all people regardless of race, color, sex, religion, disability or national origin.