Articles
THE LIMER SERIES OF ANALYTICAL PROTOCOLS FOR LIME IN CONTAINER SUBSTRATES
Article number
891_11
Pages
111 – 118
Language
English
Abstract
Limestone is used to neutralize substrate acidity, buffer pH and supplement Ca and Mg in container substrates.
The objective was to develop a series of analytical protocols for limestone in container substrates that together describe and predict pH dynamics.
The LimeR protocols include four analytical procedures (lime reactivity test, substrate lime requirement test, substrate pH buffering test, residual lime test) and an overall LimeR pH model.
The LimeR pH model is a research tool that integrates parameters generated from analytical tests in order to support decision-making.
The lime reactivity test describes the expected pH response for liming materials based on particle size efficiency and lime neutralizing value in CaCO3 equivalency.
The lime requirement test for a batch of horticultural substrate is determined using a pH titration curve with Ca(OH)2. The residual lime test protocol quantifies residual carbonate and bicarbonate (in units of CaCO3 equivalents (CCE) per liter of substrate) using a gasometric method, whereby a strong mineral acid (HCl) is applied to a substrate sample and the evolved CO2 gas can be measured by liquid volume displacement.
The substrate pH buffering test rapidly assesses substrate pH buffering capacity by measuring substrate-pH changes after a single dosage with HCl.
The LimeR pH model has been validated in experiments that compared expected and observed substrate pH using 30 commercial limestones and 10 container media.
The validation trials resulted in a close correlation and little bias between expected and observed pH values.
The LimeR protocols and model are currently being tested by commercial growing media companies.
The objective was to develop a series of analytical protocols for limestone in container substrates that together describe and predict pH dynamics.
The LimeR protocols include four analytical procedures (lime reactivity test, substrate lime requirement test, substrate pH buffering test, residual lime test) and an overall LimeR pH model.
The LimeR pH model is a research tool that integrates parameters generated from analytical tests in order to support decision-making.
The lime reactivity test describes the expected pH response for liming materials based on particle size efficiency and lime neutralizing value in CaCO3 equivalency.
The lime requirement test for a batch of horticultural substrate is determined using a pH titration curve with Ca(OH)2. The residual lime test protocol quantifies residual carbonate and bicarbonate (in units of CaCO3 equivalents (CCE) per liter of substrate) using a gasometric method, whereby a strong mineral acid (HCl) is applied to a substrate sample and the evolved CO2 gas can be measured by liquid volume displacement.
The substrate pH buffering test rapidly assesses substrate pH buffering capacity by measuring substrate-pH changes after a single dosage with HCl.
The LimeR pH model has been validated in experiments that compared expected and observed substrate pH using 30 commercial limestones and 10 container media.
The validation trials resulted in a close correlation and little bias between expected and observed pH values.
The LimeR protocols and model are currently being tested by commercial growing media companies.
Authors
P.R. Fisher, Jinsheng Huang, W.R. Argo, P.V. Nelson
Keywords
lime reactivity, limestone, peat, pH, residual lime, soil test
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