The micronutrients, or trace elements, are used in rather small amounts by plants and are not as well known. Even though these hydroponic nutrients are only needed in small amounts they are still needed none the less and are just as important to the plant as the macronutrients.
Many standard fertilizers do not contain these nutrients because standard fertilizers are designed to work with, not in place of, the dirt-bacteria environment. Here bacteria and other mechanisms supply the micronutrients. This is the main reason you should not be using any fertilizer you find without first checking for these elements.
Iron (Fe) is used during the formation of chlorophyll. An iron deficiency can cause chlorosis often called iron chlorosis.
Boron (B) is used in the formation of carbohydrates and sugars and is also involved in the regulation and use of some nutrients. A boron deficiency can cause slowed growth and may cause younger leaves to die off.
Manganese (Mn) takes part in the breakdown of carbohydrates, in the formation of chloroplasts, and used in the Nitrogen Cycle of the plant. If this cycle is disrupted it can cause a nitrogen deficiency which will lead to spots of discoloration on the leaves.
Zinc (Zn) helps regulate the consumption of sugars and is used in the transformation of carbohydrates. It is also essential in DNA transcription and is required in many enzymes. A zinc deficiency can cause stunted leaf growth or “little leaf”.
Molybdenum (Mo) helps plants use nitrogen and is important in building amino acids as a cofactor to enzymes. A deficiency of molydenum can cause the cupping or scorching of leaves and possibly chlorosis.
Copper (Cu) is important as a cofactor to many enzymes and in photosynthesis. It takes part in reproductive growth or seed development and is used in the manufacture of cell walls. A copper deficiency may cause chlorosis.
Other Nutrients
Cobalt (Co), Nickel (Ni), and Silicon (Si) are some other nutrients used by plants that currently do not appear in hydroponic nutrients. They are sometimes mentioned as plant nutrients and on occasion I will see them in hydroponics articles. Now if these nutrients are not included in hydroponic nutrients, where do plants get them from? Most likely the amounts are so small that they get enough from the seed. Or with so many things “nature will find a way”.
A component of Vitamin B12, Cobalt is needed for nitrogen fixation in legumes. Therefore a cobalt deficiency can cause symptoms similar to a nitrogen deficiency. Nickel is needed for seeds to properly germinate, so a deficiency here can cause unviable seeds. Nickel is also used in one of the enzymes used to breakdown urea, which nitrogen usable by the plant. Silicon can help protect plants against stress and can help reduce fungal diseases in some species.
For information on the macronutrients please read my article “Hydroponic Nutrients – MacroNutrients”.
It really does not matter whether a nutrient is classified as a primary or secondary nutrient or as a macro or micro nutrient. They are all needed by the plant and an abundance or deficiency of just one in your hydroponic nutrient solution cause problems or even plant death. Take the time to learn and understand the effects of all the hydroponic nutrients and you well on your way to a successful hydroponic garden.