Nutrient Basics - Molybdenum


As I wrap up my nutrient basics series of articles I want to suggest to the good growers that molybdenum and the next post on cobalt are two nutrients that may benefit the beneficial organsims as much or more than the plant it self. Molybdenum is proven to benefit symbiotic nitrogen fixation and it is used by plants for protein synthesis.

Molybdenum deficiencies show up as leaves of young plants are chloritic, leaf margins yellow and curl. Older leaves become abnormally large, while young leaves remain very small You may also notice interveinal chlorosis which occurs first on older leaves, then progresses to the entire plant. Molybdenum deficiencies frequently resemble nitrogen deficiencies, with older leaves chlorotic with rolled/curled margins and stunted growth. If you are adding a high nitrogen fertilizer during vegetative growth you should look for twisted younger leaves which eventually die which means it is molybdenum and not nitrogen..

Casues are usually due to pH, often with acidic soils (soils with a pH of 5.2 and below). An excess of sulfur or copper can also cause a molybdenum deficiency.

Molybdenum toxicity will cause a discoloration of leaves depending on plant species. This condition is rare but could occur. You will notice it right away after adding a fertilizer that is high in molybdenum. Since it is used by the plant in very small quantities, I would not recommend adding it. I say this not just to avoid harming your plant, there may be health effects from consumption of high amounts of molybdenum so if you are not 100% sure you have a deficiency, don’t worry about it.
Good Growing,
Dr. E.R. Myers

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