Plant nutrition is the study of the chemical elements and compounds necessary for plant growth, plant metabolism and their external supply. In 1972, E. Epstein defined two criteria for an element to be essential for plant growth:
- in its absence the plant is unable to complete a normal life cycle
- or that the element is part of some essential plant constituent or metabolite.
This is in accordance with Liebig's law of the minimum.[1] There are 14 essential plant nutrients. Carbon and oxygen are absorbed from the air, while other nutrients including water are typically obtained from the soil (exceptions include someparasitic or carnivorous plants). Plants must obtain the following mineral nutrients from the growing media:[2]
- the primary macronutrients: nitrogen (N), phosphorus (P), potassium (K)
- the three secondary macronutrients: calcium (Ca), sulfur (S), magnesium (Mg)
- the micronutrients/trace minerals: boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu),molybdenum (Mo), nickel (Ni)
The macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.2% to 4.0% (on a dry matter weight basis). Micro nutrients are present in plant tissue in quantities measured in parts per million, ranging from 5 to 200 ppm, or less than 0.02% dry weight.[3]
Most soil conditions across the world can provide plants with adequate nutrition and do not require fertilizer for a complete life cycle. However, humans can artificially modify soil through the addition of fertilizer to promote vigorous growth and increase yield. The plants are able to obtain their required nutrients from the fertilizer added to the soil. A colloidal carbonaceous residue, known as humus, can serve as a nutrient reservoir.[4] Even with adequate water and sunshine,nutrient deficiency can limit growth
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