Guideline Index

Chapter 3: Plant Nutrient Requirements

3.3 The essential plant nutrients

Seventeen nutrients are known to be essential for plant growth. For a nutrient to be classified as essential it must be:

  • Essential for the plant to complete its life-cycle.
  • Unique, not able to be replaced by another.
  • Required by a substantial number of plant species, not just a single species or two.
  • Directly involved in plant metabolism, that is, it must be required for a specific physiological function.

The essential nutrients can be divided into two categories:

  • Major nutrients (macronutrients).
  • Minor nutrients (micronutrients), often referred to as trace elements.

These are listed in Table 3.1. (See also Table D.1 in Appendix D.) 

Table 3.1  The essential nutrients required by plants
Table 3.1 The essential nutrients required by plants

Other minor elements, such as sodium, silicon, cobalt, strontium and barium, do not fit the criteria to be universally essential. These are called beneficial nutrients, as are the seventeen nutrients listed in Table 3.1, although the soluble compounds of some may increase plant growth. Other elements required for animal health, such as selenium, fluorine and iodine, have no known value to plants.

A deficiency in any one of the 17 essential nutrients will reduce growth and production, even though the others may be abundantly available. Optimum pasture production can only be obtained if all the requirements for plant growth are met. This fundamental principle is known as “the law of the limiting” or “Liebig’s Law of the minimum” and often represented by the barrel with uneven staves as in Figure 3.1.

Figure 3.1  Liebig’s Law of the Minimum.   (Source:
Figure 3.1 Liebig’s Law of the Minimum.(Source:

Liebig’s Law of the minimum says:

“The yield of a plant is limited by a deficiency of any one essential element, even though all others are present in adequate amounts.”

Even though Liebig’s law is discussing essential nutrients, the same principle applies to all other facets of pasture management, for example soil moisture, soil structure, grazing management and ground cover. Pasture production will not reach full potential if any one management aspect is limiting even though plant nutrients are in adequate supply.

The first three major nutrients, carbon, hydrogen and oxygen, are non-mineral and generally considered to come from carbon dioxide in the atmosphere and from water. Combined, they make up 90% to 95% of the dry matter of all plants.

The remaining nutrients are found in the soil and are taken up through the root system of the plant. However, legumes (such as clovers, lucerne and medics) also have the ability to convert atmospheric nitrogen into a plant-available form – see Section