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Essential Nutrients

Toxicities and Deficiencies | Soil pH | Soil Sampling | Nitrogen Cycle

What elements are essential for plant growth?
These elements are essential for plant growth:

  • Carbon (C)
  • Oxygen (O)
  • Hydrogen (H)
  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Sulfur (S)
  • Calcium (Ca)
  • Magnesium (Mg)
  • Iron (Fe)
  • Manganese (Mn)
  • Copper (Cu)
  • Zinc (Zn)
  • Molybdenum (Mo)
  • Boron (B)
Carbon for plant growth is obtained from the atmosphere as part of photosynthesis. Plants do not absorb carbon from the soil. Atmospheric carbon is incorporated into carbohydrate molecules and sets up the cycling of organic matter (the energy flow system) in soil.

Oxygen is gained from both the atmosphere (photosynthesis and respiration) and as a constituent of soil water. Hydrogen is also obtained from soil water. The remaining nutrients are obtained from ions dissolved in the soil solution.

Nitrogen is one important exception. Plants cannot obtain it from the atmosphere, but symbiotic Rhizobia can. Legumes can form associations with such organisms (in nodules on plant roots) and internally trade organic compounds for nitrogen.

What additional nutrients are essential for legumes?
In addition to the above,
Rhyzobia in legume nodules have a specific requirement for cobalt and molybdenum to fix nitrogen. Therefore, cobalt and molybdenum fertilisers can be needed by legumes for Rhyzobia to fix nitrogen.

What additional nutrients are essential for grazing animals?
In addition to the above, grazing animals also require these nutrients:

  • Sodium (Na)
  • Chlorine (Cl)
  • Iodine (I)
  • Fluorine (F)
  • Nickel (Ni)
  • Cobalt (Co)
  • Selenium (Se)
  • While these nutrients can be applied to the soil/plant as fertilisers, they are better supplied directly to the animal.
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