Maximum Yield USA April 2018 | Page 65

MEASURING DISSOLVED OXYGEN The dissolved oxygen concentration of a nutrient solution can be measured with a device known as a dissolved oxygen meter. A dissolved oxygen meter will give calculate the concentration in parts per million (ppm). A very general rule of thumb for hydroponic gardeners is to maintain a dissolved oxygen content of at least six to nine ppm within the nutrient solution. TEMPERATURE AND DISSOLVED OXYGEN The temperature of the nutrient solution is the most crucial physical factor associated with dissolved oxygen. Temperature inversely controls the solu- bility of oxygen in water. So, as the temperature rises, the potential dissolved oxygen content is reduced. As the temperature decreases, the potential dissolved oxygen content increases. Fully oxygenated water at 68°F can hold around nine ppm of dissolved oxygen. “A VERY GENERAL RULE OF THUMB for hydroponic gardeners is to maintain a dissolved oxygen content of at least six to nine ppm within the nutrient solution.” grow cycle 65