The pH of the nutrient solution is an important factor in hydroponics. It is a measure of the acidity and alkalinity on a scale from 1 to 14, with 1 being very acidic, 7 being neutral, and 14 being very alkaline. Most of the plants in your classroom hydroponics projects grow best when the pH of the nutrient mix is between 5.8 and 6.5. At pH readings above or below this range, certain nutrients become unavailable to plant roots. The range that allows the plant to use the dissolved minerals most effectively is just slightly acidic. pH levels vary in different nutrient mixes and water sources. If you change your nutrient solution every 10 to 21 days, as suggested, you needn't be concerned with adjusting pH, but doing so can be an engaging focus for students. You can use narrow-range pH paper, reagent type test kits, or a pH meter to do so. (Check with aquarium suppliers or science supply catalogs.) In the classroom, drops of white vinegar can lower the pH while baking soda can raise it. Hydroponic suppliers offer other products for adjusting pH.

 

pH: The Acid Test

 

 

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