Sulfur (S) Deficiency

Sulfur (S) Deficiency

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Scientific Name
Sulfur (S)
Atomic Number
16
Atomic Weight u
32.06
Elemental Group
Meso elements (Ca, Mg, S ) | Secondary macronutrients
Available Forms

Available forms of Sulfur (S) for Horticultural Production

  • Elemental sulfur (S⁰) – slow-release; requires microbial oxidation to become plant-available; used in granular or powder form.
  • Gypsum (CaSO₄·2H₂O) – moderately soluble; supplies both Ca and S; commonly used in substrate amendments.
  • Ammonium sulfate ((NH₄)₂SO₄) – highly soluble; provides both N and S; suitable for fertigation and quick substrate correction.
  • Potassium sulfate (K₂SO₄, “Sulfate of potash”) – soluble; provides both K and S; widely used in fertigation and soil mixes.
  • Magnesium sulfate (MgSO₄·7H₂O, “Epsom salt”) – soluble; provides Mg and S; rapid correction via foliar sprays or substrate application.
  • Magnesium sulfate monohydrate (MgSO₄·H₂O) – concentrated soluble source of Mg and S; used in fertigation and blending.
  • Sodium sulfate (Na₂SO₄, “Glauber’s salt”) – soluble; less commonly used in horticulture; corrective option for S deficiency.
  • Calcium polysulfide (CaSₓ) – soluble; used for sulfur supplementation and occasionally pH adjustment.
  • Chelated sulfur formulations – specialized stabilized products for rapid S uptake in foliar or fertigation programs.

Sulfur (S) Deficiency

Symptoms

  • Chlorosis: younger leaves turn pale green to yellow first (unlike nitrogen deficiency, which affects older leaves).
  • Leaves may show reddish or purplish tinges on veins, petioles, or margins.
  • Stunted growth, thin stems, and reduced branching; plants appear spindly with poor canopy coverage.
  • Leaves become smaller, thinner, and less vibrant.
  • Delayed flower initiation and smaller blooms; in severe cases, brittle stems and poor bract or flower development.

Causes

  • Low sulfur availability in substrates, especially in soilless mixes with little organic matter (peat, coir, bark).
  • Modern fertilizers often lack sulfur (e.g., pure nitrate salts such as calcium nitrate or potassium nitrate).
  • Leaching: sulfate is highly soluble and easily washed from container media by frequent irrigation.
  • Reduced atmospheric sulfur deposition has lowered natural background supply.
  • Low microbial activity limiting conversion of elemental sulfur to sulfate in container systems.

Correction

  • Foliar sprays: Apply soluble S sources such as magnesium sulfate (Epsom salts, MgSO₄·7H₂O) or ammonium sulfate ((NH₄)₂SO₄) for rapid relief.
  • Substrate amendments: Use gypsum (CaSO₄·2H₂O), potassium sulfate (K₂SO₄), or controlled-release fertilizers containing sulfate.
  • Balanced fertilization: Incorporate S-containing fertilizers into fertigation (e.g., 20-20-20 with sulfate forms).
  • Monitor irrigation to avoid excessive leaching of sulfates.
  • Maintain a proper Ca:Mg:S ratio to avoid nutrient antagonisms.

Prevention

  • Include sulfur routinely in fertilization programs; avoid exclusive reliance on sulfate-free nitrate fertilizers.
  • Use complete fertilizers supplying 50–80 ppm S for container and bedding plants.
  • Periodically test substrate and plant tissue to confirm adequate sulfur nutrition.
  • Prevent over-irrigation that increases sulfate leaching from substrates.
  • Ensure balanced fertilization with correct ratios of calcium, magnesium, and sulfur.

Sulfur (S) Deficiency

Sulfur (S)
Scientific Name
Sulfur (S)
Atomic Number
16
Atomic Weight u
32.06
Elemental Group
Meso elements (Ca, Mg, S ) | Secondary macronutrients
Available Forms

Available forms of Sulfur (S) for Horticultural Production

  • Elemental sulfur (S⁰) – slow-release; requires microbial oxidation to become plant-available; used in granular or powder form.
  • Gypsum (CaSO₄·2H₂O) – moderately soluble; supplies both Ca and S; commonly used in substrate amendments.
  • Ammonium sulfate ((NH₄)₂SO₄) – highly soluble; provides both N and S; suitable for fertigation and quick substrate correction.
  • Potassium sulfate (K₂SO₄, “Sulfate of potash”) – soluble; provides both K and S; widely used in fertigation and soil mixes.
  • Magnesium sulfate (MgSO₄·7H₂O, “Epsom salt”) – soluble; provides Mg and S; rapid correction via foliar sprays or substrate application.
  • Magnesium sulfate monohydrate (MgSO₄·H₂O) – concentrated soluble source of Mg and S; used in fertigation and blending.
  • Sodium sulfate (Na₂SO₄, “Glauber’s salt”) – soluble; less commonly used in horticulture; corrective option for S deficiency.
  • Calcium polysulfide (CaSₓ) – soluble; used for sulfur supplementation and occasionally pH adjustment.
  • Chelated sulfur formulations – specialized stabilized products for rapid S uptake in foliar or fertigation programs.
Sulfur (S) Deficiency
Image Source: Everris Research (NL), LVG Heidelberg (D) care of ICL

Sulfur (S) Deficiency

Symptoms

  • Chlorosis: younger leaves turn pale green to yellow first (unlike nitrogen deficiency, which affects older leaves).
  • Leaves may show reddish or purplish tinges on veins, petioles, or margins.
  • Stunted growth, thin stems, and reduced branching; plants appear spindly with poor canopy coverage.
  • Leaves become smaller, thinner, and less vibrant.
  • Delayed flower initiation and smaller blooms; in severe cases, brittle stems and poor bract or flower development.

Causes

  • Low sulfur availability in substrates, especially in soilless mixes with little organic matter (peat, coir, bark).
  • Modern fertilizers often lack sulfur (e.g., pure nitrate salts such as calcium nitrate or potassium nitrate).
  • Leaching: sulfate is highly soluble and easily washed from container media by frequent irrigation.
  • Reduced atmospheric sulfur deposition has lowered natural background supply.
  • Low microbial activity limiting conversion of elemental sulfur to sulfate in container systems.

Correction

  • Foliar sprays: Apply soluble S sources such as magnesium sulfate (Epsom salts, MgSO₄·7H₂O) or ammonium sulfate ((NH₄)₂SO₄) for rapid relief.
  • Substrate amendments: Use gypsum (CaSO₄·2H₂O), potassium sulfate (K₂SO₄), or controlled-release fertilizers containing sulfate.
  • Balanced fertilization: Incorporate S-containing fertilizers into fertigation (e.g., 20-20-20 with sulfate forms).
  • Monitor irrigation to avoid excessive leaching of sulfates.
  • Maintain a proper Ca:Mg:S ratio to avoid nutrient antagonisms.

Prevention

  • Include sulfur routinely in fertilization programs; avoid exclusive reliance on sulfate-free nitrate fertilizers.
  • Use complete fertilizers supplying 50–80 ppm S for container and bedding plants.
  • Periodically test substrate and plant tissue to confirm adequate sulfur nutrition.
  • Prevent over-irrigation that increases sulfate leaching from substrates.
  • Ensure balanced fertilization with correct ratios of calcium, magnesium, and sulfur.