Goal: Use the saturated paste extract method (SPE) to test substrate pH and electrical conductivity (EC) for container-grown plants. This method is also called the saturated medium extract (SME).
Plants are very sensitive to substrate-pH and EC. Low substrate-pH level may lead to micronutrient toxicities, whereas deficiencies in micronutrients are common at high pH. Plants will become deficient in nutrients if substrate-EC remains low. High EC can lead to salt burn of roots, root diseases and stunted growth.
Step 1. Requirements
Step 2. Sample collection
Step 3. Add distilled water into substrate samples to the saturation point
Step 4. Measure pH and EC
The Saturated Paste Extract method is commonly used by laboratories. The SPE can also be successfully conducted onsite by growers, so long as careful attention is paid to how the sample is prepared.
To ensure the highest quality data, the testing procedures need to be consistent.
Acceptable pH range for greenhouse floriculture plants
EC value (mS/cm) for greenhouse floriculture plants
Target EC levels are lower for slow-growing plants, and crops grown with controlled-release fertilizers. A range from 1.0 to 1.5 mS/cm is recommended for woody ornamentals by Mylavarapu, R. and T. Yeager. 2011. UF/IFAS Extension Nutrient Management Series: Container Media Nutrient Test Interpretation. EDIS Bulletin SL180, edis.ifas.ufl.edu.
For more information: Contact authors Jinsheng Huang and Paul Fisher of University of Florida IFAS Extension. Thanks to our Floriculture Research Alliance at University of Florida sponsors including A.M.A. Plastics, Blackmore Co., Everris, Fafard et Frères Ltd (Canada), Fine Americas, Greencare Fertilizers, Pindstrup, PremierTech Horticulture, Quality Analytical Laboratories, Sun Gro Horticulture, and leading young plant growers. August 23, 2014.