The Basics of Lime Testing

The majority of our soils in the Great Lakes region require regular liming in order to maintain pH levels that are within the appropriate range to maximize crop growth and productivity. The quality and effectiveness of a liming material can vary tremendously depending on the source, composition, and physical properties of the material, so having a reliable lime analysis is critical to ensure that the proper type and quantity of liming material is used to get the desired effect.

Agricultural lime quality is usually measured by three characteristics:
 

1. Purity - commonly expressed as calcium carbonate equivalent (CCE)

2. Particle size – finer particles react more quickly to raise soil pH

3. Moisture – increases weight of the material without increasing effectiveness, essentially “diluting” the material

 
A number of materials can be used to increase the pH of the soil, but historically the most common material is ground limestone, commonly referred to as ag lime. Ag lime is finely ground rock containing high levels of calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃). It is actually the carbonate (CO₃^-) in lime that reacts with acidity (hydrogen) to increase soil pH.

Calcium and magnesium in lime, in addition to being essential plant nutrients, exchange with hydrogen (H⁺) held on cation exchange sites, moving H⁺ into soil solution where it can be neutralized by carbonate.

Particle size determines how quickly lime will dissolve and react in the soil. Generally, 40-50% of the particles in a good quality liming material will pass through a 60-mesh sieve. States in this region have different lime quality systems, with state-specific terminology and measurements.

A&L Great Lakes offers a Fact Sheet, entitled Adjusting Lime Rates, which provides details on how to make adjustments. A & L Great Lakes has also developed a spreadsheet which outlines various states’ systems and helps adjust rates for a particular liming material. These useful tools are available from our website at www.algreatlakes.com.