A soil analysis will tell whether a field needs lime to raise the soil pH. The lime rate per acre will be determined from the buffer pH or lime test index of the soil analysis. Lime recommendations are generally given as tons per acre.
Any lime source may be used to correct soil acidity; however, lime sources will vary in price and quality of material. The Ohio Department of Agriculture evaluates all liming sources sold commercially in Ohio. Part of the evaluation process requires an analysis of the lime material to determine its effectiveness to neutralize soil acidity in a timely manner, which will be reported as the Effective Neutralizing Power (ENP). A retailer selling lime in Ohio is required to have the ENP value as part of the lime analysis and have the lime analysis available for the buyer. The value will be expressed as pounds per ton. The ENP value incorporates all quality components of lime: purity (calcium and magnesium content), particle size, and water content. The ENP allows producers to compare different liming sources regardless of differences in purity, fineness of grind or water content between sources.
To determine the amount of lime needed with the ENP value use the following equation:
Tons of lime material = (Lime rate from soil test) * (2000/ENP)
The actual cost of a lime source may also be used with ENP by the following equation:
Cost ($/acre) = (Lime rate from soil test/ (ENP/2000)) * ($/ton)
Economics and the ability to evenly apply the material should be the primary factors in selecting a lime source. Calcium content and magnesium content of a lime source should not matter unless the soil analysis shows a need for one of these nutrients. If the soil test magnesium levels are less than 50 ppm (100 lbs) then dolomitic lime should be use since it will cost considerably less than other magnesium sources. Hi cal (calcitic) lime should be used if the percentage of base saturation of calcium from the soil analysis is equal to or lower than the percentage of base saturation of magnesium. If the soil test does not show a special need for magnesium or calcium then select the least expensive lime source for your area whether it be dolomitic or hi-cal.
Since ENP incorporates grind size in its formula, pelletized lime may be compared to regular lime sources. Pelletized lime is a regular lime source that has been ground to a finer particle size and held together by a binder to form a pellet. A pelletized lime will also have an ENP value from the lime analysis sheet. The lime rate for pelletized lime will use the same formula as regular lime to determine the tons of material by using the ENP value.
Lime recommendations from soil testing laboratories assume a soil incorporation depth of eight inches. Rates should be adjusted for incorporation depths less than eight inches. For no-till fields or lime left on the surface, assume 4 inch incorporation. Adjust your lime rate by the following equation:
Lime rates for < 8 inches incorporation = (Soil test lime rate/8) * lime incorporation depth
More detailed information on lime may found in the OSU Fact Sheet: Soil Acidity and Liming for Agronomic Production (http://ohioline.osu.edu/agf-fact/0505.html)
Recommendations and the lime discussion in this article are for Ohio. Lime regulations often vary from state to state and may be different than Ohio.