This Unit is about Micro- nutrients in Agriculture.



Sources of iron.

  • Rock materials
  • Organic matter
  • Iron
  • Most irons are rick in poorly aerated soils concentrating may reach toxic levels.
  • Volcanic soils are also rich in iron.

Importance of iron.

  1. Chlorophyll formation.
  2. It activates a number of important respiratory enzymes.

Un availability of iron to plants may be caused by:-

  • Excess manganese copper or zinc
  • Abundant sandy materials

Deficiency of iron

Severe chlorosis especially in young leaves.


Originates from weathering of rocks.

High acidity toxicity

High alkalinity deficiency.

Importance of manganese

  • Its associates with plant respiratory enzymes.
  • Increase availability of calcium, magnesium and phosphorous.
  • Essential for certain nitrogen transformation in plants and micro organisms.
  • Catalyst in chlorophyll formation.

Deficiency of manganese

  1. Stunted growth
  2. Failure to reproduce
  3. Molted chlorosis in younger leaves.


Zinc is essential for the normal healthy growth and reproduction of plants, animals and humans and when the supply of plant-available zinc is inadequate, crop yields are reduced and the quality of crop products is frequently impaired.

Released from weathering and farm yard manure.

Importance of Zinc

  • Chlorophyll formation
  • Stem elongation and normal development of growth hormones.
  • Concerned with reproductive process in certain

Deficiency of Zinc

  1. Common in alkaline soils and heavy leached soil.
  2. Young leaves are almost entirely without chlorophyll
  3. In woody plants, shoots do not elongate.

Excess zinc is toxic


Copper (Cu) is an essential nutrient for plant growth, but because only a small amount is needed, it is classified as a micronutrient. Most Minnesota soils contain adequate amounts of this nutrient for optimum crop yields.

Organic or peat soils are exceptions and Cu might be needed in a fertilizer program when small grains are grown on these soils. Wheat is the most sensitive to Cu deficiency. Although barley and oat crops are less sensitive, Cu use will increase their yield when grown on organic soils.


Available from weathered minerals especially in acidic soils.

Importance of copper.

  • Chlorophyll formation
  • Consistent of some plants enzymes.
  • Involved in respiration.
  • Controls utilization of iron

Deffiency of copper

  1. Results in die black woody tissues.
  2. Twings begin to die and leaves turn yellow green colour

Excess copper toxic


Boron is an essential micronutrient for growth and development of healthy plants. In small concentrations boron compounds are used as micronutrients in fertilizers, in large concentrations they are used as herbicides, algaecides and other pesticides.

Release during rock weathering

Accumulates in organic matter.

Importance of Born

  • All division
  • Its associated with calcium utilization
  • Plays apart in water absorption and translocation of sugar

Defficiency of Boron

  • Common in leached soils
  • Common in soils with low organic matter content. During the dry season when organic matter decomposition i.e. limited deffiences occur.
  • Stunted growth.
  • Death of terminal bud.
  • Shortening of inter nodes.


  • Released from weathering  and accumulation of organic matter.
  • More available in alkaline soils in acidic soils its fixed by iron.
  • Application of phosphatic and sulphur fertilizers increased up take of
  • Molybdenum by plants.

Importance of molybdernium.

  • Essential in symbiotic nitrogen fixation.
  • Plays an important part in enzyme systems.
  • Important in protein formation.

Associated with nitrogen deficiency and its symptoms.


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