• Wear gloves and eye protection when handling dry powder or concentrated solutions
• Avoid inhaling dust — use in well-ventilated areas or wear a dust mask when measuring large quantities
• Wash hands thoroughly after handling

• Store in a cool, dry place in the original sealed container or airtight bag
• Product is hygroscopic — it will absorb moisture from the air if left exposed
• Keep out of direct sunlight and away from heat sources
• Keep away from children and pets

• Dissolve completely in water before adding to hydroponic or fertigation systems to avoid clogging
• Do not mix concentrated stock solutions with calcium-containing fertilizers (forms insoluble calcium sulfate)
• Avoid foliar application in direct sunlight or during peak heat — spray early morning or late evening
• Water thoroughly after soil application to move nutrients into the root zone

• Eye contact: Flush with clean water for 15 minutes. Seek medical attention if irritation persists
• Skin contact: Wash affected area with soap and water
• Ingestion: Do not induce vomiting. Contact Poison Control (1-800-222-1222) or seek medical attention
• Inhalation: Move to fresh air. Seek medical attention if symptoms persist

Refer to the Safety Data Sheet (SDS) for complete safety information.

Potassium sulfate (0-0-53) is a premium potassium fertilizer containing 53% K₂O and 17% sulfur, with virtually no chloride content. Unlike muriate of potash (potassium chloride), which contains about 47% chloride, potassium sulfate is safe for chloride-sensitive crops including tobacco, potatoes, tomatoes, berries, and citrus where chloride reduces sugar content and storage life. While more expensive than muriate of potash, the quality improvements and yield benefits often justify the cost for high-value crops. For a deeper comparison of potassium fertilizer options, see our guide on What is the Best Potassium Fertilizer?

Timing varies by crop, but key application periods include:

• Fruit trees: Split applications — early spring and during fruit development
• Vegetables: At planting and again during fruit or tuber formation
• Grapes: From veraison (color change) through harvest for quality enhancement
• Field crops: Pre-plant or side-dress during rapid growth
• Lawns & perennials: Late summer or fall to improve winter hardiness

Potassium is especially important during fruit development, as it directly improves size, color, sugar content, and storage quality. Late-season applications enhance crop quality without promoting excessive vegetative growth.

Potassium plays multiple critical roles in plant health: it controls stomatal function for efficient water use, activates over 60 enzymes involved in growth, drives CO₂ fixation and sugar transport during photosynthesis, thickens cell walls for disease resistance, and enhances drought, cold, and salt tolerance. Plants with adequate potassium show improved resistance to fungal diseases, better recovery from environmental stress, and enhanced winter survival. For a complete explanation, see our article What's the Function of Potassium (K) in Plants?

Yes, potassium sulfate is excellent for hydroponics due to its complete water solubility and dual nutrient content. It provides both potassium and sulfur without adding chloride, won't clog drippers or emitters when properly dissolved, and is compatible with most hydroponic nutrients. Typical rates are 2–3 tablespoons per gallon, contributing approximately 0.7–1.0 mS/cm to EC. Always dissolve completely in warm water before adding to your reservoir, and keep it in a separate stock tank from calcium-based fertilizers.

Potassium deficiency symptoms typically appear on older leaves first and include marginal chlorosis (yellowing or browning of leaf edges), necrotic spots, weak stems prone to lodging, poor fruit quality (small size, poor color, low sugar), increased disease susceptibility, and reduced overall yields. Deficiency is most common in sandy soils, after heavy rainfall, or when high nitrogen rates are used without balanced potassium. Soil tests showing less than 150 ppm K typically indicate supplementation is needed.

The 17% sulfur in potassium sulfate is a valuable secondary nutrient that supports protein synthesis, amino acid formation (cysteine and methionine), enzyme activation, and vitamin production. Sulfur also helps lower alkaline soil pH, improving the availability of phosphorus, iron, and other pH-sensitive nutrients. For crops like garlic, onions, and brassicas, adequate sulfur directly enhances flavor and nutritional quality. For more on sulfur's role, read Secondary Nutrients in Gardening: Complete Guide to Ca, Mg, & S.

Not in concentrated stock solutions. When potassium sulfate is mixed with calcium-containing fertilizers (like calcium nitrate) in a concentrated tank, the sulfate ions react with calcium to form insoluble calcium sulfate (gypsum) that precipitates out and clogs irrigation lines. In hydroponic and fertigation systems, always use separate A and B stock tanks — potassium sulfate goes in Tank B, calcium nitrate goes in Tank A. In soil applications at normal dilution rates, this interaction is not a concern.

For premium fruit production, potassium sulfate is strongly preferred over potassium chloride (muriate of potash). Chloride can reduce sugar content, degrade flavor profiles, shorten storage life, and cause salt buildup in soils. Potassium sulfate delivers equivalent potassium without these drawbacks, plus provides beneficial sulfur. The higher cost per pound is offset by improved fruit quality and market value. For a complete analysis of how potassium impacts fruit production, see our article on What Types of Fertilizers Should I Use to Improve Fruit Yield?

• Manufactured in Madera, California, USA
• Tested by independent third-party laboratories for purity
• Registered with the California Department of Food and Agriculture (CDFA)
• Rigorously tested for heavy metal content
• Premium-grade crystalline form with complete water solubility

If you're not completely satisfied, we offer a 90-day money-back guarantee. Simply return the unused portion in its original packaging, and we'll process a full refund. No questions asked.

• Recyclable packaging materials
• Precise nutrient formulation to reduce environmental runoff
• Chloride-free formula prevents soil salt accumulation
• Support for integrated pest management (IPM) practices

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