Molybdenum: The Essential Trace Mineral Your Plants Crave

  • , by Agriplex India
  • 5 min reading time

Molybdenum

Soil is made up of 45 % minerals, 25 % water 25 % air, and the remaining 5 % Organic Matter, because of organic matter, the soil is said to be biological live. In the earth there are 92 naturally occurring chemical elements, among these 17 essential minerals are very much required for plants (Figure-1) further these nutrients are classified based on the requirements of the plant. Primary nutrients are Carbon, Hydrogen, and Oxygen are obtained naturally from the Air and Water. Major essential elements are Nitrogen, Phosphorus, and Potassium. Secondary nutrients are Calcium, Magnesium, and Sulfur. Micronutrients are Iron, Zinc, Manganese, Copper, Boron, Molybdenum, Chlorine, and Nickle are supplied either from soil minerals and soil organic matter or by organic or inorganic fertilizers.

These essential nutrients play a specific role in plant metabolic activities if deficiency of any nutrients can not be substituted with other nutrients.  However, if any one of the essential nutrients is failed to supply during the crop life cycle, may significantly affect the plant growth and may not get the desired yield.

In this topic we shall discuss one such essential Micro nutrient called Molybdenum which is also called Ultra micronutrient required by plants in the least concentrations of 0.1 ppm (1/1000000), we shall try to understand the source, plant uptake form, functions, and deficiency symptoms.

Source     

In agricultural soils, Molybdenum is available 0.5 to 5 mg Mo/kg.  molybdenum is present in many different complexes depending on the chemical specification of the soil zone. Release of molybdenum from solid mineral forms is through weathering.  Primary soluble soil form is molybdate anion (MoO42–) and availability is pH dependent, Molybdenum availability tends tending increase tenfold for each unit increase in soil pH i.e., it is the only micronutrient that is more available if soil pH is greater than 6. Whereas in the acid soils, pH is less than 6, Molybdenum is strongly absorbed by Iron (Fe), and Aluminum (Al) oxides become unavailable to plant uptake.

Fertilizer Forms

Multiplex Molybdenum (Ammonium molybdate 52%), Sodium molybdate (41%), Molybdenum trioxide (66%Mo), Molybdic acid(53%Mo) 

Role of Molybdenum

  • Molybdenum is a necessary component of more than 40 enzymes out of which two major enzymes in plants, nitrate reductase and nitrogenous, which are required for normal assimilation of Nitrogen in plants.
  • In non-leguminous plants helps in the assimilation of Nitrate to amino acids and proteins.  
  • Molybdenum is necessary for the process of symbiotic nitrogen fixation by Rhizobia bacteria in legume root modules.
  • Molybdenum helps in nodule formation in legumes and increases the size of the nodules.
  • In leguminous crops during symbiotic Nitrogen fixation, molybdenum co-factors the synthesis of enzymes which assists in the conversion of elemental Nitrogen into ammonium (NH4+) ions.
  • Molybdenum helps to synthesis Ascorbic acid (Vitamin C), especially for citrus and lemon plants
  • In coffee crops Molybdenum plays a significant role in the assimilation of Nitrogen resulting in new flush, better berry development, and increased yield.
  • Molybdenum helps in the synthesis of sugars, Indole-3-acetic acid, and regulates the synthesis of Abscisic acid which controls plants against abiotic stress.  
  • Mo supply can strengthen plant metabolism at different growth stages through an improved enzymatic and non-enzymatic antioxidant defense system and enhance other pharmacological/medicinal properties of the plant.
  • It is evident that Tomato Molybdenum sprays help to induce disease resistance against Verticillium wilt

Deficiency symptoms

  • Occurs in acid soils (Low pH) sandy soil and leached soils. Using excess sulphate fertilizers can induce Molybdenum deficiency.
  • Mo deficiency symptoms often resemble N deficiency symptoms with stunted growth, chlorosis poor development of nodules in legumes
  • In grapevines, molybdenum deficiency shows a bunch development disorder called Millerandage or ‘hen and chicken’ it is characterized by grapevine bunches showing the uneven size of the berries.
  • Grapes vines showing Millerandage disorder also show symptoms of shortened zigzag-shaped inter nodes, pale-green leaves, increased cupped and flaccid leaves, and marginal leaf necrosis
  • In cauliflower, the middle lamella of the cell wall is not formed completely when Molybdenum is deficient, with only the leaf rib formed, thereby giving a whiptail appearance.
  • In maize, molybdenum deficiency shortens internodes, decreases leaf areas, and causes the development of chlorotic leaves
  • Mo deficiency in citrus is commonly called "yellow spot." The deficiency occurs when trees are unable to absorb sufficient Mo from an acidic soil. Deficiency symptoms appear on the leaves as large, interveinal chlorotic spots.
  • The inhibition of pollen formation with molybdenum deficiency may explain the lack of fruit formation in molybdenum-deficient watermelon.
  • In coffee plants bright yellow spots develop near leaf margins and between leaf veins. These areas can turn necrotic. Leaves become distorted and narrow, rolling downwards. Older leaves are affected first.
  • In molybdenum-deficient tomatoes, lower leaves appear mottled and eventually cup upward and develop marginal necrosis.

Management

To overcome Molybdenum deficiency, use Multiplex Molybdenum which contains (Ammonium Molybdenum 52 %),

Foliar Spray: Dissolve 0.5 g in one litre of water and spray on leaves liberally 20 to 30 days after germination/transplantation.

Seed Treatment: Apply about 1 g per kg of seed. Use Maxiwet/ Nagastha- 180 as sticking.

Fertigation: Use Multiplex Molybdenum 100 g/ acre through drip.  

Conclusion

The availability of molybdenum is pH dependent, and only Micronutrients are available above pH 7. Molybdenum increases Nitrogen fixation, helps to assimilate nitrogen to synthesize amino acids, proteins, chlorophyll pigments, and enzymes, and enhances absorption of other nutrients from the soil and seed treatment with molybdenum is beneficial for all types of leguminous/ vegetables. Early application of Molybdenum through spraying helps in robust plant growth and development, induces more flowering, increases pollen fertility, and induces resistance against pest and diseases in Cereals, Horticultural, Plantation, and floriculture crops.

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