Three Criteria for Essentiality of Nutrients:
- A plant cannot complete its life-cycle in the absence of the element
- The action of the element must be specific, with no other element being able to completely substitute for it
- The element must be shown to be directly involved in the nutrition of the plant. It must be a constituent of a metabolic pathway or at least be required for the activity of an essential enzyme.
Eighteen Essential Nutrients for Plant Growth
There are 18 essential nutrients for plant growth: 3 structural, 6 macronutrients, and 9 micronutrients
Plants need large amounts of macronutrients relative to other essential nutrients.
- Three structural are: Carbon (C), Hydrogen (H), Oxygen (O)
- Six macronutrients are from soil: Nitrogen (N), Phosphorus (P), Potassium (K), Magnesium (Mg), Calcium (Ca), Sulfur (S)
Compared with macronutrients, the concentrations of the nine (9) micronutrients in plants may be very small. This does not mean they are not important. Deficiencies or excesses of the micronutrients can cause yield loss just as macronutrient deficiencies or toxicities. Micronutrients are often considered enzyme nutrients:
- All micronutrients are from soil
- Six micronutrients are cations: Copper (Cu), Manganese (Mn), Iron (Fe), Zinc (Zn), Nickel (Ni), Cobalt (Co)
- Three micronutrients are anions: Chloride (Cl), Boron (B), Molybdenum (Mo).