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ROLE OF COBALT IN AGRICULTURE
Rhizobia and other nitrogen (N)-fixation bacteria require Co and cobalamin for fixing atmosphere dinitrogen (N 2) into ammonia (NH 3), providing plants with the essential macronutrient of N. Co plays a vital role in interaction with iron, nickel, and zinc in maintaining cellular homeostasis.
Cobalt: An Essential Micronutrient for Plant Growth?
Cobalt has been considered an essential element for prokaryotes, human beings, and other mammals. Co is essential for the growth of many lower plants, such as marine algal species including diatoms, chrysophytes, and dinoflagellates, as well as for higher plants in the family Fabaceae or Leguminosae.
The essentiality of leguminous plants is attributed to their role in nitrogen (N) fixation by symbiotic microbes, primarily rhizobia. Cobalt is an integral component of cobalamin or vitamin B12, which is required by several enzymes involved in N2 fixation.
Functions of cobalt
1. Cobalt is required for symbiotic and non-symbiotic nitrogen fixation.
2. It is a part of vitamin B-12.
3. It improves growth, transpiration, and photosynthesis.
4. Take parts in leg hemoglobin metabolism and ribonucleotide reductase.
The symptoms of cobalt deficiency in plants tend to be vague, but may include the following:
• Stunted growth.
• Reddening of stems.
• Uniform paling, yellowing, or reddening of leaves.
• Small root nodules on legumes.
• Nitrogen deficiency symptoms in legumes.
• Reduced seed production.
• Reduced germination of the next generation of seeds in dry conditions.
Most forages are a good source of cobalt with a range of 0.1-0.3 mg/kg DM, or ppm. Poorly drained soils tend to lead to higher concentrations of cobalt in herbage grown on these soils. Over-liming soils to increase the pH above 6.0 will reduce the availability of cobalt and may lead to deficiency.
Cobalt cannot be synthesized by the body and hence must be derived from food. Umpteen dietary resources contain ample volumes of cobalt, namely cruciferous vegetables like cabbage, and lettuce, whole grain cereals such as barley, oats, dairy produce, animal meat, fish, oysters, and eggs.