PI Ed Dan Sullivan
OSU Dept. of Crop and Soil Science

Co-PI Aaron Heinrich
OSU Dept. of Horticulture

Executive Summary

Several new powdered limestone products that are more finely ground (smaller particle size distribution) than products historically used have become commercially available. A major factor influencing the effectiveness of a liming material is its particle size distribution, with smaller particles reacting more quickly. Because lime efficiency estimates for various particle size fractions were established in the 1950’s, there is a need to evaluate current guidelines to determine if they adequately predict liming efficiency for these new products. The objective of this study was to assess the reactivity of commercially available powdered lime products (both calcitic and dolomitic) and various particle size fractions over a year with the goal of evaluating current OSU lime guidelines.

The products evaluated included two produced from Ashgrove Cement Company (Ashgrove Ag Lime and Ashgrove Ground Dolomite) and two finely-ground limes produced by Columbia River Carbonates (Microna Ag H2O and Microna Ag Lime sold under the trade name Access lime). Of these products, Ashgrove Ag lime is the most widely utilized in the Willamette Valley. The following particle size fractions (US mesh) of calcitic limestone were also evaluated: 10-20, 20-40, 40-60, 60-100, and 100-200. The performance (ability to increase soil pH or exchangeable Ca (X-Ca)) of the lime products and particle size fractions were evaluated in field and laboratory studies.

Initially the dolomitic lime was the least reactive product (this is due to the low solubility of magnesium carbonate relative to calcium carbonate), but was equal in performance to other products at 12 months. Although the Microna products were generally more reactive than the Ashgrove Ag lime at 1 month, from 3 months on there were little or no differences in pH or XCa between products. In our study, there was no observed increase in lime performance for particles <20 mesh (i.e., all particles <20 mesh performed equally) measured at 12 months.