• Wear safety glasses or goggles when handling powder to avoid eye contact
• Use chemical-resistant gloves during mixing and application
• Wear a dust mask or N95 respirator when measuring or mixing fine powder in enclosed areas
• Long sleeves and pants recommended during field applications
• Wash hands, forearms, and face thoroughly after handling

• Store in original, sealed container in a cool, dry, well-ventilated area
• Keep away from direct sunlight and heat sources
• Store separately from incompatible materials (strong oxidizers, strong bases)
• Keep out of reach of children and pets
• Do not store near food, feed, or potable water

• Do not apply foliar sprays during heat stress, drought stress, or when plants are wilting
• Do not apply to deciduous tree crops during bloom — may cause phytotoxicity
• In hydroponics, excessive Mn can antagonize iron and zinc uptake — stay within 0.5–2 ppm range
• Manganese toxicity can occur in waterlogged, very acidic soils — do not apply if soil pH is below 5.5 without testing
• Avoid runoff into waterways, storm drains, or aquatic environments

• Eye contact: Immediately flush with clean water for 15–20 minutes, holding eyelids open. Seek medical attention if irritation persists
• Skin contact: Wash affected area with soap and water. Remove contaminated clothing. Seek medical attention if irritation develops
• Ingestion: Do not induce vomiting. Rinse mouth with water. Contact Poison Control (1-800-222-1222) or seek medical attention immediately
• Inhalation: Move to fresh air immediately. Seek medical attention if breathing difficulty, coughing, or irritation persists

For chemical emergencies contact CHEMTREC: +1-703-527-3887. Refer to the Safety Data Sheet (SDS) for complete safety information.

Manganese sulfate is a water-soluble micronutrient fertilizer providing 31% manganese and 18% sulfur. Manganese is essential for the oxygen-evolving complex of photosystem II — the water-splitting reaction that powers photosynthesis and enables plants to convert light into energy. Without it, plants cannot function normally. Manganese also activates more than 30 plant enzymes involved in nitrogen metabolism, chlorophyll function, and structural support through lignin formation. The sulfur component contributes to protein synthesis and can support local acidifying effects in the rhizosphere over time, which may improve manganese availability in alkaline soils.

For a deeper look at how manganese and potassium interact in plant nutrition, see: What is the Role of Manganese and Potassium?

Frizzle top is a progressive manganese deficiency disorder affecting palms. New fronds emerge chlorotic, undersized, and weak in the early stage. As deficiency worsens, fronds become withered, scorched, and distorted — the "frizzled" appearance that gives the condition its name. In advanced cases, only small brown stubs emerge from the spear, eventually leading to palm death.

Most susceptible species are Queen Palms, Royal Palms, Pygmy Date Palms, Paurotis, and Coconut Palms. Because manganese is immobile in plant tissue, deficiency symptoms always appear on new growth first — making early intervention critical. Preventive applications every 3 months are more effective than trying to rescue severely affected palms.

The most reliable indicator is interveinal chlorosis on young leaves — the tissue between veins turns yellow or pale green while the veins themselves remain green. This contrasts with iron deficiency, which looks similar but can be distinguished by soil pH and the specific crop affected. Other symptoms include gray specks or necrotic spots on leaf tissue (common in cereals), stunted growth, reduced fruit set, and delayed maturity.

Manganese deficiency is most common in soils with pH above 7.0, sandy soils with low organic matter, over-limed soils, and waterlogged soils where Mn converts to unavailable oxidized forms. A soil or tissue test is the most reliable confirmation before applying. For more on diagnosing nutrient deficiency symptoms, see: 8 Reasons Why Your Plant Leaves Are Turning Yellow

Foliar spray is often the most efficient method for rapid correction — 1–3 lbs per 100 gallons delivers manganese directly to leaf tissue, with visible improvement in new growth often appearing within 1–2 weeks. Best applied before full leaf expansion. Always test on a small area first.

Soil application (20–60 lbs/acre broadcast, 10–30 lbs/acre banded, based on soil test) is longer lasting but less efficient due to soil tie-up in high-pH conditions. Adding 50+ lbs/acre ammonium sulfate can significantly improve Mn availability. For palms, apply 2–16 oz per tree to soil under the canopy every 3 months. For hydroponics, target 0.5–2 ppm in the completed nutrient solution — use the calculator on this page for exact dosing.

To understand how sulfur works alongside manganese in plant nutrition, see: What is the Function of Sulfur in Plants?

The 50 lb size of our manganese sulfate is repackaged from OMRI Listed® material, which means it may be suitable for use in certified organic production where soil manganese deficiency is documented. Other sizes carry CDFA registration but are not repackaged from OMRI Listed® material.

Organic compatibility requirements vary by certifying agency. Always verify current approval status with your certifier before use, and keep documentation of your soil deficiency on file as most certifiers require it to justify micronutrient applications.

Manganese sulfate (MnSO₄) releases Mn²⁺ ions directly into the soil solution. It is cost-effective and works well in moderately acidic to neutral soils (pH 5.5–7.0) where ionic manganese remains available. In soils above pH 7.0, Mn²⁺ can rapidly oxidize to unavailable Mn⁴⁺ forms, reducing effectiveness.

Chelated Manganese EDTA binds manganese in an organic cage that resists pH-driven oxidation, keeping Mn plant-available across a wider pH range including alkaline soils. Chelated forms cost more per unit but the difference is justified in high-pH conditions where sulfate forms would be largely immobilized. For a detailed comparison of sulfate and chelated micronutrient sources, see: Sulfate vs. Chelated Fertilizers

• Registered with the California Department of Food and Agriculture (CDFA)
• 50 lb size repackaged from OMRI Listed® material — suitable for certified organic production
• Independently tested for heavy metals by third-party laboratories — results consistently well below required limits
• Over 99% purity — fine crystalline powder
• Consistent particle size for uniform dissolution and application
• Packaged at our facility in Madera, California

If you're not completely satisfied with your purchase, we offer a 90-day money-back guarantee. Return the unused portion in its original packaging and we'll process a full refund — no questions asked.

• Biodegradable packaging materials
• Precise nutrient formulation reduces excess application and potential runoff
• Support for eco-friendly and sustainable farming practices
• No unnecessary fillers or additives — pure active ingredient

1% of all profits go to our foundation, focused on improving educational opportunities for children.

With over 35 years in business, Greenway Biotech, Inc. is a family-owned specialty fertilizer and wellness products manufacturer based in Madera, California. We hold CDFA registration for our fertilizer line and are committed to third-party testing, technical accuracy, and regulatory compliance — making us a trusted source for commercial growers and home gardeners alike.

Learn more about our story →