By Bob Battel
As harvest progresses throughout the state, farmers can take advantage of the open ground to apply lime to acidic soils. Liming acidic soils to a near neutral pH (6.5 - 6.8) is one of the most important practices in managing soil fertility according to Michigan State University Extension. Properly limed soils have improved nutrient availability, microbial activity and overall soil productivity.
Traditionally, farmers use ground calcitic limestone (CaCO3) or dolomitic limestone (MgCO3●CaCO3) to reduce soil acidity. Some farmers may have the opportunity to use byproducts of municipal water softening, or sugar beet processing to lime their soils. Growers can use these materials effectively to raise soil pH. These materials are often available to farmers for less expense than agricultural lime. Often the farmer pays a small fee, plus trucking, or perhaps pays only trucking charges for the byproduct lime. However, users should be aware of the properties of these materials, and be prepared to handle them differently than ground agricultural lime.
Municipal water treatment can include the use of hydrated lime to remove dissolved calcium and magnesium ions from the water, thus softening it. Farmers can use the resulting byproduct as a liming agent. The acid neutralizing value of the water treatment lime can be similar to, or even greater than ground ag lime. The material is also very fine, and dissolves and reacts quickly in the soil solution.
By the nature of its production, water treatment lime is very wet – 40-50% moisture. Because of its wet, fine particles, water treatment lime can be difficult to spread in a uniform fashion, resulting in bands of heavy lime alternating with bands of light lime applied throughout the field. These bands can ultimately result in areas of very high soil pH. Care should be taken to ensure an even spread. A special spreader designed to handle wet materials may be needed. Because the product dissolves so quickly, users may consider using less of the product than a soil test recommends and apply the product more frequently. Agricultural lime contains a range of particle sizes to raise and maintain the soil pH over a 3-to-5-year period. Water treatment lime will raise the pH quickly, but not maintain it.
Lime is also used in processing sugar beets to remove impurities from the sugar. The resulting byproduct is a liming material that generally has a lower acid neutralizing value than agricultural limes. Therefore, the beet lime should be spread at a greater per acre rate than traditional ground agricultural lime. Beet lime contains fine particles so reacts quickly in the soil, but may not maintain the soil pH as long as ag lime. Beet lime can also have a lot of moisture, and similar to water treatment lime, care should be taken to ensure an even spread.
Knowing the Neutralizing Value (NV) of a lime source is useful in calculating spreading rates for lime sources. Pure, finely ground CaCO3 has an NV of 100. Typical agricultural limes, with minor impurities and an array of particle sizes, has an NV of 90. Soil test recommendations for spreading lime are based on a material with an NV of 90. Water treatment and sugar beet limes have neutralizing values of up to 120 and 80-90, respectively. Hence, it takes less water treatment lime, and often more sugar beet lime to neutralize acid soils.