• Wear gloves when handling dry product to avoid skin irritation
• Use eye protection (safety glasses or goggles) during application
• Wear a dust mask when spreading dry product in windy conditions
• Wash hands thoroughly after handling

• Store in a cool, dry place in the original sealed container
• Product may absorb moisture if exposed — keep container tightly closed
• Keep out of direct sunlight and away from heat sources
• Keep away from children and pets

• Avoid direct contact with plant stems and foliage when applying to soil
• Water thoroughly after soil application to prevent root irritation
• Do not exceed recommended application rates
• Avoid blending with calcium nitrate or high-calcium fertilizers unless compatibility has been confirmed; these combinations may be incompatible in blended or solution applications

• 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.

K-Mag (sulfate of potash magnesia, also called langbeinite fertilizer or potassium magnesium sulfate) is a naturally mined mineral fertilizer with a guaranteed analysis of 22% potassium (K₂O), 11% magnesium (Mg), and 22% sulfur (S). Its triple-nutrient profile is unique because it delivers potassium without nitrogen — ideal during fruit development and ripening. The low chloride content (less than 2.5%) makes it a preferred low chloride potassium fertilizer for chloride-sensitive crops like tobacco, potatoes, tomatoes, and berries, where higher-chloride sources like muriate of potash may cause chloride-related stress.

Choose K-Mag when growing chloride-sensitive crops (tobacco, potatoes, tomatoes, peppers, berries), when magnesium is also needed, for late-season soil fertilization when nitrogen isn't desired, or on sandy and acidic soils low in both magnesium and sulfur. K-Mag also helps prevent grass tetany in pastures where magnesium is crucial for livestock health. For a deeper look at how potassium benefits your crops, see our guide on What's the Function of Potassium (K) in Plants?

K-Mag works through three complementary nutrient pathways. Potassium (22% K₂O) regulates water uptake, supports drought tolerance, and enhances fruit size and overall plant resilience under stress. Magnesium (11% Mg) is the central component of chlorophyll and supports phosphorus utilization — deficiency shows first as interveinal chlorosis on older leaves. Sulfur (22% S) is required for protein synthesis, enhances nitrogen efficiency, and improves crop flavor and aroma. In potassium- or magnesium-deficient soils, correcting these nutrients with K-Mag can help improve yield and tuber quality, including reduced internal brown spot in potatoes.

Potassium deficiency appears as yellowing or browning of leaf edges (marginal chlorosis), weak stems, poor fruit quality, and increased susceptibility to stress. Magnesium deficiency shows as interveinal chlorosis on older leaves first, with reduced photosynthesis and poor fruit set. Sulfur deficiency causes uniform yellowing of young leaves (unlike nitrogen deficiency which affects older leaves first), stunted growth, and delayed maturity. Soil-test thresholds vary by lab and soil type, but deficient or low K and Mg levels are a strong signal to consider K-Mag application. For more on magnesium deficiency, read What's the Function of Magnesium (Mg) in Plants?

K-Mag is compatible with most dry fertilizers including urea, ammonium sulfate, DAP, MAP, and most micronutrients. Avoid blending with calcium nitrate or high-calcium fertilizers unless compatibility has been confirmed; these combinations may be incompatible in blended or solution applications. K-Mag is primarily intended for soil application. For fully water-soluble potassium needs — such as fertigation or foliar feeding — consider MKP 0-52-34 or Potassium Sulfate 0-0-53 instead.

Manganese activates enzymes involved in carbohydrate metabolism and root health, which supports efficient potassium uptake. When manganese levels are adequate, plants develop root systems better equipped to absorb potassium from the soil. This relationship is especially important in high-carb crops like potatoes and corn. For a detailed look at this nutrient interaction, see Why High-Carb Crops Demand Plenty of Potassium (and How Manganese Can Help).

Langbeinite is a naturally mined mineral input that may be allowed in organic production depending on certification rules. Always verify with your certifying body (such as OMRI or your local organic certification program) before use, as requirements can vary by program and region.

• Sourced from premium-grade natural langbeinite mineral deposits
• Independently tested by third-party laboratories for purity and nutrient content
• Independently lab tested for heavy metal content
• Registered with the California Department of Food and Agriculture (CDFA)
• Packaged in our facility in Madera, California

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
• Natural mineral source with low chloride and no added nitrogen
• Less soluble than fully water-soluble salts — nutrient release is generally more gradual, which may help reduce rapid nutrient movement compared with highly soluble alternatives

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

Family-owned since 1989. Making gardens — and their humans — healthier for over 35 years.