ISHS Acta Horticulturae 779: International Symposium on Growing Media
EVALUATION OF LIMESTONE PHYSICAL AND CHEMICAL PROPERTIES ON NEUTRALIZATION CAPACITY |
| Authors: | J.F.M. Rippy, P.V. Nelson, T.E. Bilderback, D.L. Hesterberg, E.J. Kamprath, WM.H. Swallow, D. Jahn |
| Keywords: | calcium/magnesium content, density, hardness, porosity, size, soundness, specific surface |
| Abstract:
Although several physical and chemical properties of limestone have been shown to affect limestone neutralization capacity, particle size distribution and CaCO3 content have been deemed adequate measures to classify agricultural limestones. When using agricultural limestone to neutralize substrate acidity in horticultural endeavors, problems of inconsistent initial pH in substrates created using standard formulas for limestone additions, and pH drift from the initial target in those substrates, occur. This study was conducted to evaluate the effects particle size, CaCO3 and MgCO3 content, internal porosity, hardness, soundness, specific gravity, and specific surface of limestones from twenty quarries (selected to maximize differences in properties) on limestone reactivity in order to determine the degree of influence of these factors on neutralization capacity of the limestones. Data for all these physical/chemical properties were analyzed in multiple regressions with particle size included and with particle size held constant at coarse [30–50 mesh (600–300 µm)], medium [170–200 mesh (90–75 µm)], and fine [325–400 mesh (45–38 µm)] fractions. Particle size accounted for slightly more than half of the neutralization capacity of the limestones. With particle size held constant, CaCO3 or MgCO3 had the greatest impact on limestone reactivity, accounting for about 50% of the reactivity. Specific surface did not correlate significantly to particle size, thus addressed an additional aspect of limestone reactivity. Porosity, hardness and bulk density were highly correlated to each other, thus measured the same aspect of limestone reactivity. Soundness had little influence on reactivity. Adding specific surface measurements to particle size and CaCO3 content increased the power of the reactivity prediction model to 83% of the reactivity. The addition of a fourth measurement; either porosity, hardness or bulk density, increased the model strength to only 88%. Adding specific surface measurements to the description of limestones used for horticultural purposes would be advantageous. | |
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