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SHORTCUTS

What are plant nutrients?

The essential nutrients

Sixteen nutrients are essential for the growth of most plants. They are derived from the surrounding air, water and soil.

  • From air: carbon as carbone dioxide (CO2)
  • From water: hydrogen and oxygen
  • From soil, fertilizer and animal manure:
    • nitrogen N
    • phosphorus P
    • potassium K
    • calcium Ca
    • magnesium Mg
    • sulphur S
    • iron Fe
    • manganese Mn
    • zinc Zn
    • copper Cu
    • boron B
    • molybdenum Mo
    • chlorine Cl
    Other chemical elements are also taken up by plants. While these elements are beneficial to some plants, they are not essential to the growth of all of them.

The role of nutrients

Soils may be naturally low in nutrients, or they may become deficient due to nutrient removal by crops over the years without replenishment - or when high-yielding varieties are grown that have higher nutrient requirements than do local varieties.

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2 main types of nutrients

The two main types of nutrients

All of the essential nutrients are important but in varying quantities

  • Macronutrients are needed by plants in large quantities. The "primary nutrients" are nitrogen, phosphorus, and potassium. Today, sulphur is also considered a key macronutrient. Macronutrients include both primary and secondary nutrients.
  • Micronutrients (or "trace elements") are required in very small amounts for correct plant growth. They need to be added in small quantities when they are not provided by the soil.

Every plant nutrient, whether required in large or small amounts, has a specific role in plant growth and food production. One nutrient cannot be substituted for another.

Nitrogen N

Nitrogen is the motor of plant growth. It is taken up from the soil in the form of nitrates or ammonium. As the essential constituent of proteins, nitrogen is involved in all the major processes of plant development and yield formation.

Phosphorus P

Phosphorous performs a key role in the transfer of energy. It is essential for photosynthesis and other chemico-physiological. Phosphorous is indispensable for cell differentiation, as well as for the development of the tissues that form a plant's growing points. Most natural and agricultural soils are phosphorus deficient. When there are problems with phosphorous fixation, this also limits its availability.

Potassium K

Potassium activates more than 60 enzymes, (the chemical substances that govern life and play a vital part in carbohydrate and protein synthesis). It improves a plant's water regime and increases tolerance to drought, frost and salinity. Plants that are well supplied with potassium are less affected by disease.

Sulphur S

Sulphur is an essential constituent of protein. It is also involved in the formation of chlorophyll. Sulphur is as important in plant growth as phosphorous and magnesium, but its role has often been underestimated.

Magnesium Mg

Magnesium is the central constituent of chlorophyll, the green pigment in leaves that functions as an acceptor of the energy supplied by the sun: 15-20% of the magnesium in a plant is found in the green parts. Magnesium is also involved in enzyme reactions related to energy transfer.

Calcium Ca

Calcium is required for root growth and as a constituent of cell wall materials. Most soils contain sufficient plant-available calcium. Deficiencies may occur in strongly calcium-depleted tropical soils. Calcium is usually applied to limit or reduce soil acidity.

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