Importance of Limestone Specific Surface for Assessing Neutralization Effectiveness in Soilless Root Substrate

The relationship of specific surface to particle diameter and calcium carbonate (CaCO₃) content of limestone was examined. Limestones obtained from 20 North American quarries were wet sieved into eight particle diameter fractions (600 to ?38 µm). Specific surface of particles was measured in each fraction following the Brunauer-Emmett-Teller theory. The range in specific surface across the 20 sources varied from 74-fold in the coarsest particles (600–300 µm) to 20-fold in the finest particles (?38 µm). The pattern of specific surface progressing from the coarsest to the finest particles varied radically between sources. The relationship between specific surface and CaCO₃ content was likewise very weak. While particle diameter and CaCO₃ equivalent remain the traditional measurements for defining limestone for field production, specific surface provides additional information valuable to define the stricter neutralization capacities of limestone for soilless root substrates.