These factors determine the quantity of salts being "active" and available to the plants. As the plant nutrients, like nitrate, potassium, etc., are salt ions, the measurement of "active" salt ions gives an immediate information about the plant nutrition status.
The measuring principle of "activity" has been developed by Prof. Dr. Tepe, a former director of the Research Institute for Soil Science and Plant Nutrition Geisenheim, Germany. Since then this method has been applied as an easy, fast and reliable control of plant nutrition.
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