SECONDARY NUTRIENTS AND MICRONUTRIENTS FOR INDOOR HYDROPONICS
The primary nutrients of a plant are nitrogen (N), Phosphorus (P) and Potassium. Plants require these in larger amounts than the secondary nutrients: sulfur (S), magnesium (Mg), and calcium (Ca). Both primary and secondary nutrients are called macronutrients. Micronutrients aid plant chemistry at much lower concentrations than the macronutrients. For basic information on macronutrients, see this post.
THE SECONDARY NUTRIENTS
Soil generally contains sufficient quantity of these secondary nutrients. However for the hydroponics gardener, indoor or out, you must supply these as well.
Among other actions, sulfur is required to produce chlorophyll. It is also the cause of the distinctive taste of many vegetables, including onions and garlic.
Another necessary mineral for the production of the chlorophyll molecule, correct magnesium levels are also critical for reactions producing fats and carbohydrates.
Calcium aids in cell growth and division. It is also required to take up nitrogen and other minerals. It plays an important role in the movement of water in cells.
All the secondary nutrients are important for the funciton of enzymes. Enzymes are proteins that catalyze biochemical reactions, i..e, help them occur in the internal environment of the plant.
THE MICRONUTRIENTS
A partial list follows of the micronutrients: iron (Fe), manganese (Mn), zinc (Zn), boron (B), and copper (Cu).
Iron is another critical component in the production of chlorophyll in a plant.
Manganese supports the absorption of the macronutrient nitrogen.
Zinc, again is a nutrient which is involved in enzymatic processes in the cell. Zinc is also involved in the formation of auxins, plant hormones stimulating grownth, as well as carbohydrate metabolism and protein synthesis.
Boron is involved in a broad range of biochemical activities, including but not limited to cell wall formation, membrane integrity and calcium uptake.
Found primarily in plant root, copper is involved in nitrogen metabolism.
FORM OF MACRONUTRIENTS AND MICRONUTRIENTS
Plants require these minerals to be dissolved in water. Therefore fertilizers are in the form of salts. A salt is a which when dissolved in water breaks up into ions.
WARNING REGARDING THESE NUTRIENTS
This is not a case of the “more the better”. Excess amounts can kill your plants. Err on the side of caution. Unless you get recommendations specific to hydroponics methods, reduce the amount given to 1/4 to 1/3 of the amount recommended. Doing this your first indoor hydroponics exeriences should be good ones.