Article Index
Foliar Nutrition
Reasons for deficiency
Plant Nutrients
Requirements & signs of deficiencies
Symptoms of nutrient deficiencies
Trace element deficiency table
Influence of the least nutrient
The influence of pH
The effect of pH
Absorbition of nutrients IONS
All Pages

Plant Nutrients

Basic elements
Ninety-two natural mineral elements are known to exist, but only sixty of these have been found in plants. Of these sixty, only sixteen are considered essential for plant growth.

To be considered essential for healthy plant growth, an element must fulfill four criteria.

  • It must be necessary for the plant to complete it's life cycle.
  • It's action must be specific, that is, not wholly replaceable by any other element.
  • It must be directly involved in the nutrition of the plant, that is, required for the action of an essential enzyme.
  • It must not antagonise the toxic effect of another element.

The sixteen elements that are generally considered essential for plant growth are divided into macro-elements (those that are required in relatively large quantities) and micro-elements or trace elements (those required in considerably smaller quantities.)
Macro-nutrients Micro-nutrients
carbon (C) boron (B)
hydrogen (H) chlorine (Cl)
oxygen (O) copper (Cu)
nitrogen (N) iron (Fe)
phosphorus (P) manganese (Mn)
potassium (K) molybdenum (Mo)
calcium (Ca) zinc (Zn)
magnesium (Mg)
sulphur (S)

Essential Elements; The lack of just one essential element can ruin the chances of a good crop, even if all the other essential nutrients are there.
Before deciding which plant nutrients should be provided for in a plant it is necessary to know the function of each element.
The macro-nutrients and micro-nutrients are almost always taken up by the plant in the form of ions, which are positively or negatively charged particles.

Macro-nutrients are those which the plants need in large quantities and consist of the following:

images/stories/flower.gif Calcium (Ca)
Responsible for the structural and physiological stability of the plant tissue ; for efficient cell division, cell wall formation and cell extension. It sometimes interferes with the ability of magnesium to activate enzymes.
images/stories/flower.gif Carbon (C)
A constituent found in all organic compounds.
images/stories/flower.gif Hydrogen (H)
A constituent of all organic compounds of which carbon is a constituent. It is important for the cation exchange in plant-medium relations.
images/stories/flower.gif Magnesium (Mg)
As the central atom of chlorophyll (leaf green), it is of particular importance in the process of photosynthesis. It also promotes the absorption and translocation of phosphorus, and appears to aid in the formation of oils and fats. It supports the assimilation of carbon dioxide(CO2) and the synthesis of protein.
images/stories/flower.gif Nitrogen (N)
Nitrogen is used in various forms to promote rapid vegetative growth, leaf, flower, fruit and seed development,and chlorophyll development, and to increase the protein content in all plants. Nitrogen is absorbed in the form of ammonium (NH4), nitrate (NO3) or urea (CO(NH2) 2).
images/stories/flower.gif Oxygen (O)
A constituent of many organic compounds. It is essential in the anion exchange between roots and the external medium.
images/stories/flower.gif Phosphorus (P)
It promotes and stimulates early growth and blooming and root growth. It hastens maturity and seed growth, and it contributes to the general hardiness of the plant.
images/stories/flower.gif Potassium (K)
It promotes disease resistance and good development of carbohydrates, starches and sugars, and it increases fruit production. It is also instrumental in regulating the plant's water retention.
images/stories/flower.gif Sulphur(S)
As a constituent of amino acids, sulphur promotes the synthesis of protein. Sulphur deficiency symptoms are therefore similar to nitrogen deficiency. It also promotes the synthesis of soils and good cell wall structure.

Micro-nutrients consist of the following:

images/stories/flower.gif Boron(B)
Promotes the formation of protein which is required in order to sustain meristem activity (meristem is embryonic tissue). Being part of the cell walls, it promotes the transfer of carbohydrates through the cell membranes and supports the assimilation to supply the roots and is important for blossom formation.
images/stories/flower.gif Chlorine(Cl)
Is essential for photosynthesis where it acts as an enzyme activator during the production of oxygen from water.
images/stories/flower.gif Copper(Cu)
Participates in the production of carbohydrates and proteins via photosynthesis; 70% of the copper in a plant is in the chlorophyll. It is also thought to be involved in nitrogen fixation.
images/stories/flower.gif Iron(Fe)
Acts as a catalyst in the photosynthesis and respiration process, and is essential for the formation of sugars and starches. Iron also activates certain other enzymes.
images/stories/flower.gif Manganese(Mn)
Activates one or more enzymes in fatty acid synthesis and the enzymes responsible for DNA and RDA formation. It also participates directly in the photosynthetic production of oxygen from water and may be involved in chlorophyll formation. Manganese is closely associated with copper and zinc.
images/stories/flower.gif Molybdenum(Mo)
Essential for the activation of nitrate reductase, which is the conversion of nitrate into nitrite. There is a higher Mo requirement when NO3 is supplied as a feed than with NH4. It's most important function is the fixation of nitrogen, particularly in legumes.
images/stories/flower.gif Zinc(Zn)
Similar to magnesium and manganese in its physiological activity, it influences the formation of starch and the synthesis of RNA, so promoting the production of protein.