Variability of Soluble Salts Using Different Extraction Methods on Composts

Compost Science & Utilization, (2004), Vol. 12, No. 2, 180-184

Kara L. McLachlan1, Calvin Chong2, R. Paul Voroney1, Hua-Wu Liu3 and Bruce E. Holbein3

1. University of Guelph, Department of Land Resource Science, Guelph, Ontario
2. University of Guelph, Department of Plant Agriculture, Guelph, Ontario
3. Eastern Power Ltd./Super-Blue-Box-Recycling Company (SUBBOR), Guelph, Ontario

Soluble salts represent dissolved inorganic ions in solution and are typically measured in terms of electrical conductivity (EC). Often soluble salt measurements from different studies or laboratories cannot be cross-referenced or there is much confusion when comparing these results. The soluble salts from 13 composts and horticultural substrate materials were extracted using six different methods: saturated medium extract; pour-through, a water displacement method; and water suspensions using various ratios (by volume) of water:substrate (1:1, 1:2, 2;1, 5:1). EC ranged from 0.1 (peat and perlite) to 23.1 dS m-1 (turkey litter compost). A linear regression model was developed to allow cross-referencing between extraction methods of measurements of soluble salts concentration of the composts and substrates.

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