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Electrical Conductivity (EC) A short background on Electrical Conductivities (ECs)- they are a simple way to estimate how much salt (fertilizer) is in the irrigation water. EC is actually measuring how well the solution conducts electricity, and the EC probe cannot distinguish between a solution with high calcium from one with high sodium. EC must be considered as an estimate of the total fertilizer content of the irrigation water. Just to confuse the issue, ECs can be reported in several different units of measure. But fortunately, all of the units are easily converted from one to another. The scientific literature tends to favor µS/cm (microSiemens per centimeter) as the unit of measure, but those values are identical to an older unit called micromhos per centimeter (µmhos/cm) (1µS/cm = 1 µmho/cm). The change from one system to another started in the 1970’s. Sometimes, milliSiemens per centimeter (mS/cm) is used, which is just µS/cm x 1000 (1 mS/cm = 1000 uS/cm). Other units include “total dissolved solids” (TDS) or “parts per million” (PPM), which are both simply calculations assuming certain salts are present in “normal” relative proportions. In general, to convert from µS/cm to PPM, simply multiply the µS/cm value by 0.64. To convert from mS/cm to PPM, multiply mS/cm by 640 (1 mS/cm = 640 PPM).

Indeterminate Plants -plants that have a vine-like character. Contrast to a bush-like character, called a “determinate” plant. These terms come from the botanical terminology referring to plants that cease growing larger as soon as flowers are produced, so their size and shape is “determined” by flowering. Indeterminate plants continue growing even after flowers are set)

Additional Glossaries

(1) or
(2) MSU’s glossary of greenhouse terms