Agricultural Nutrient Profile: Micronutrients-Part 1

Posted in: Agronomy and Soil Health

An introduction to micronutrients in crop production

While much of the focus around fertilizer programs involves macronutrients (nitrogen, phosphorus, and potassium) and secondary nutrients (calcium, magnesium, and sulphur) – one cannot underestimate the importance of micronutrients in crop production.

There are several micronutrients that are essential for proper crop development. These are:

  • Boron (B): Plays a central role in germination of pollen grains and pollen tube growth. Needed for seed and cell wall formation and sugar translocation.
  • Chlorine (Cl): Is required by all plants in small quantities and is available as chloride. It is involved in energy reactions.
  • Cobalt (Co): Required for stem growth and coleoptile elongates, which contribute to overall growth and CO2
  • Copper (Cu): Necessary for enzyme function, cell wall formation, electron transport and oxidation reactions.
  • Iron (Fe): Required many enzyme functions involving energy transfer, nitrogen reduction and fixation, and lignin formation.
  • Manganese (Mn): Involved in several enzyme systems and metabolic reactions. Necessary for photosynthesis. Speeds up germination and maturity. Increases P and Ca availability.
  • Molybdenum (Mo): Needed for the enzyme nitrate reductase. Required for symbiotic nitrogen fixation involving Rhizobia.
  • Zinc (Zn): Required for a complex array of plant functions involving enzymes, leaf and bud development, production of IAA (Indoleacetic Acid) and calcium absorption.

Availability of micronutrients

Inorganic micronutrients exist naturally in the soil. As minerals break down, micronutrients become readily available to the plant in 2 types- adsorbed onto soil colloids (very small soil particles) and in the form of salts dissolved in the soil solution. Decomposing organic matter is another secondary source of micronutrients.

Availability and uptake of micronutrients in crop production can be reduced in soils that:

  • Are low in organic matter (less than 2.0%)
  • Have high levels of organic matter (over 30% to a depth of 30 cm)
  • Are cool and/ or wet
  • Have a high pH level (molybdenum is an exception)

Source: Alberta Agriculture and Forestry

Next: Spotlight on Zinc, Boron, Copper, and Manganese

In the next part of this series we go into more detail, focusing on four micronutrients in crop production that are the most likely candidates for deficiency in western Canada: zinc, boron, copper, and manganese.

We will look at the function of these micronutrients, factors that impact the availability of each, as well as strategies to address deficiencies.

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