This Crop File discusses the factors and calculations used to identify the relative “quality” of various materials used as agricultural lime (aglime) sources. (See also Crop File 2.03.001, “Agricultural Liming Materials – Terms”.)
Size distribution influences agronomic effectiveness (see Fig. 4 and Fig. 5).
Coarse particles react very slowly and have essentially no neutralizing value.
Medium size particles dissolve slowly and neutralize pH over a longer time period (e.g., 3 to 5 years)
Fine particles react and dissolve quickly to neutralize soil acidity in short time (e.g., 1 to 2 years).
Seems to be little agronomic advantage for grinding coarse lime to particles finer than 60 mesh.
Particles finer than 100 mesh appear to have same agronomic effectiveness over time as 60 to 100 mesh particles.
Some lime sources have large proportion of very fine particles (e.g., sugar beet process lime, water softening lime), but may be difficult to apply uniformly due to moisture content.
Fineness factor = percentage (by weight) of liming material that will pass designated sieves, multiplied by specific “effectiveness” factor.
Effectiveness ratings based on amount of lime likely to react in one year.
Aglime particles should be fine enough to dissolve within four to five years after application.
Each effectiveness factor based on range of particle size.
Coarse particles ≈ 0% to 10% effective.
Medium particles ≈ 20% to 60% effective.
Fine particles ≈ 90% to 100% effective.
State laws specify specific effectiveness factor for specific range of sieve sizes.
Fineness factors for each particle size range are added together to obtain single fineness factor for lime source.