Molybdenum (Mo) Deficiency

Molybdenum (Mo) Deficiency

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Scientific Name
Molybdenum (Mo)
Atomic Number
42
Atomic Weight u
95.95
Elemental Group
Micro elements (B, Cl, Cu, Fe, Mn, Mo, Ni, Zn) | Micronutrients
Available Forms

Available forms of Molybdenum (Mo) for Horticultural Production

  • Ammonium molybdate [(NHâ‚„)₆Mo₇O₂₄·4Hâ‚‚O] – highly soluble; widely used in foliar sprays and fertigation programs.
  • Sodium molybdate (Naâ‚‚MoO₄·2Hâ‚‚O) – soluble; effective for substrate incorporation or foliar correction.
  • Potassium molybdate (Kâ‚‚MoOâ‚„) – soluble; supplies both K and Mo, occasionally used in fertigation solutions.
  • Molybdenum trioxide (MoO₃) – less soluble; incorporated into granular or slow-release fertilizers for long-term supply.
  • Chelated molybdenum (Mo-EDTA, Mo-DTPA, Mo-EDDHA) – stabilized forms; effective across a wider pH range for fertigation or foliar use.
  • Molybdic acid (Hâ‚‚MoOâ‚„) – soluble; occasionally included in micronutrient blends or substrate amendments.
  • Mo-enriched micronutrient blends – controlled-release or combined formulations supplying Mo with other trace elements.

Molybdenum (Mo) Deficiency

Container Nursery Stock, Pot & Bedding Plants

Symptoms

  • Older leaves show pale green or yellowing, often with interveinal chlorosis.
  • Leaf margins may curl, cup, twist, or become distorted; crinkling may occur in severe cases.
  • Stunted growth, shortened internodes, reduced branching, and smaller leaves.
  • Poor or delayed flowering; abnormal flower formation in severe deficiencies.
  • Necrotic spots, marginal burn, or dieback can develop in advanced cases.

Causes

  • Mo is required for nitrate reduction and other enzymatic functions; deficiency is most common in acidic substrates (pH < 5.5).
  • Low Mo levels in sandy, leached, or aged substrates with poor micronutrient supply.
  • Excessive nitrogen, particularly ammonium-based fertilizers, can antagonize Mo uptake.
  • High levels of iron, manganese, aluminum, or sulfur may reduce Mo availability.
  • Waterlogged or poorly drained soils limiting root uptake.

Correction

  • Foliar sprays: Apply soluble Mo salts such as ammonium molybdate or sodium molybdate for rapid recovery.
  • Substrate incorporation: Add small amounts of Mo-containing fertilizers to the growing medium for sustained supply.
  • pH management: Adjust substrate to slightly acidic to neutral (pH 6.0–7.0) to improve Mo availability.
  • Fertilizer balance: Moderate nitrogen inputs and avoid excess ammonium to encourage uptake.

Prevention

  • Include molybdenum in routine micronutrient or balanced fertilizer programs.
  • Regularly monitor substrate pH and maintain within the optimal 6.0–7.0 range.
  • Avoid over-application of antagonistic fertilizers (ammonium-N, Fe, Mn, Al).
  • Test substrate and plant tissue periodically to ensure adequate Mo levels and detect early signs of deficiency.
  • Maintain proper irrigation practices to prevent nutrient leaching or waterlogging.

Molybdenum (Mo) Deficiency

Molybdenum (Mo)
Scientific Name
Molybdenum (Mo)
Atomic Number
42
Atomic Weight u
95.95
Elemental Group
Micro elements (B, Cl, Cu, Fe, Mn, Mo, Ni, Zn) | Micronutrients
Available Forms

Available forms of Molybdenum (Mo) for Horticultural Production

  • Ammonium molybdate [(NHâ‚„)₆Mo₇O₂₄·4Hâ‚‚O] – highly soluble; widely used in foliar sprays and fertigation programs.
  • Sodium molybdate (Naâ‚‚MoO₄·2Hâ‚‚O) – soluble; effective for substrate incorporation or foliar correction.
  • Potassium molybdate (Kâ‚‚MoOâ‚„) – soluble; supplies both K and Mo, occasionally used in fertigation solutions.
  • Molybdenum trioxide (MoO₃) – less soluble; incorporated into granular or slow-release fertilizers for long-term supply.
  • Chelated molybdenum (Mo-EDTA, Mo-DTPA, Mo-EDDHA) – stabilized forms; effective across a wider pH range for fertigation or foliar use.
  • Molybdic acid (Hâ‚‚MoOâ‚„) – soluble; occasionally included in micronutrient blends or substrate amendments.
  • Mo-enriched micronutrient blends – controlled-release or combined formulations supplying Mo with other trace elements.
Molybdenum (Mo) Deficiency
Image Source: NCSU (USA), PPO Boskoop (NL), WUR Glastuinbouw, Bleiswijk (NL), care of ICL

Molybdenum (Mo) Deficiency

Container Nursery Stock, Pot & Bedding Plants

Symptoms

  • Older leaves show pale green or yellowing, often with interveinal chlorosis.
  • Leaf margins may curl, cup, twist, or become distorted; crinkling may occur in severe cases.
  • Stunted growth, shortened internodes, reduced branching, and smaller leaves.
  • Poor or delayed flowering; abnormal flower formation in severe deficiencies.
  • Necrotic spots, marginal burn, or dieback can develop in advanced cases.

Causes

  • Mo is required for nitrate reduction and other enzymatic functions; deficiency is most common in acidic substrates (pH < 5.5).
  • Low Mo levels in sandy, leached, or aged substrates with poor micronutrient supply.
  • Excessive nitrogen, particularly ammonium-based fertilizers, can antagonize Mo uptake.
  • High levels of iron, manganese, aluminum, or sulfur may reduce Mo availability.
  • Waterlogged or poorly drained soils limiting root uptake.

Correction

  • Foliar sprays: Apply soluble Mo salts such as ammonium molybdate or sodium molybdate for rapid recovery.
  • Substrate incorporation: Add small amounts of Mo-containing fertilizers to the growing medium for sustained supply.
  • pH management: Adjust substrate to slightly acidic to neutral (pH 6.0–7.0) to improve Mo availability.
  • Fertilizer balance: Moderate nitrogen inputs and avoid excess ammonium to encourage uptake.

Prevention

  • Include molybdenum in routine micronutrient or balanced fertilizer programs.
  • Regularly monitor substrate pH and maintain within the optimal 6.0–7.0 range.
  • Avoid over-application of antagonistic fertilizers (ammonium-N, Fe, Mn, Al).
  • Test substrate and plant tissue periodically to ensure adequate Mo levels and detect early signs of deficiency.
  • Maintain proper irrigation practices to prevent nutrient leaching or waterlogging.