Salt levels in the root substrate can be measured using an electrical conductivity (EC) meter. A high substrate-EC may result from excess fertilizer or contaminants such as sodium and chloride in the irrigation water. High EC leads to salt burn to plant roots, and toxicity symptoms in the foliage. This outline discusses the causes and corrections of high substrate-EC. Test corrective actions on a small group of plants first, and as a long-term strategy rely on prevention rather than cure.
Test substrate-EC and pH using a standard procedure and a calibrated meter to confirm it is a high EC issue. Target EC ranges vary between testing methods and crop types. Evaluate plant appearance. Typical symptoms of high salts are stunted overall growth, dark green and thick leaves, marginal burn and yellowing on older leaves, and limited root growth or damaged root tips. Other causes such as pesticide phytotoxicity or low pH can give symptoms similar to high EC, so run an onsite soil test and evaluate crop history.
Avoid the combination of high substrate-EC with low substrate-pH: this practice could result in high deposits of both macronutrients (e.g. N, P and K) and micro-nutrients (e.g. iron and manganese), resulting in micronutrient toxicity for iron-efficient crops (like geraniums and marigold).
For more information: Contact authors Jinsheng Huang and Paul Fisher of University of Florida IFAS Extension, and Dr. Bill Argo of Blackmore Co. Thanks to our Floriculture Research Alliance at University of Florida sponsors including A.M.A. Plastics, Blackmore Co., Everris, Fine Americas, Greencare Fertilizers, Klasmann-Deilmann, Pindstrup, Premier Tech Horticulture, Quality Analytical Laboratories, Sun Gro Horticulture, and leading young plant growers. The University of Florida does not endorse any product, and our research focuses on quality testing on these and competing products to assist grower success. June 30 2015.