What Is Potash
Potash is a broad term for potassium compounds used in fertilizers and agriculture. The name comes from the historical practice of soaking plant ashes in pots to extract potassium salts. Today, potash is mined from underground deposits and processed into several fertilizer forms.
In fertilizer terminology, potash refers to the potassium content expressed as K2O (potassium oxide). When a fertilizer bag reads 10-10-10, the third number (10) represents 10 percent potash, meaning 10 percent of the bag’s weight is potassium oxide equivalent.
What Potash Does for Plants
Potassium is essential for three critical plant functions. First, it regulates water movement in and out of cells (osmotic regulation), which directly affects drought tolerance. A potassium deficient lawn wilts faster and recovers slower during dry periods.
Second, potassium strengthens cell walls, making grass blades and stems physically tougher. This improves wear tolerance on high traffic lawns and resistance to fungal diseases that penetrate weak cell walls.
Third, potassium activates enzymes involved in photosynthesis and energy transfer. Without adequate potassium, grass cannot efficiently convert sunlight into the sugars it needs for growth and root development.
Types of Potash Fertilizer
| Type | Chemical Formula | K2O Content | Other Nutrients | Best For |
|---|---|---|---|---|
| Muriate of Potash (MOP) | KCl | 60 to 62% | Chloride | Most lawns and gardens (cheapest option) |
| Sulfate of Potash (SOP) | K2SO4 | 50 to 52% | Sulfur (18%) | Chloride sensitive plants, gardens |
| Potassium Nitrate | KNO3 | 44% | Nitrogen (13%) | Dual feeding situations |
| Wood Ash | Variable | 3 to 7% | Calcium, trace minerals | Organic gardens, soil pH increase |
| Greensand | Glauconite | 3 to 5% | Iron, trace minerals | Slow release organic option |
When Your Lawn Needs Potash
A soil test is the only reliable way to determine potassium levels. Most lawn soils in the Midwest contain adequate potassium, but sandy soils, heavily irrigated lawns, and soils with low organic matter often test low. Your county extension office offers soil testing for $10 to $25.
Visual symptoms of potassium deficiency include yellowing of older leaf blades starting at the tips and margins, increased susceptibility to drought stress, slow recovery from mowing or traffic, and higher than normal disease incidence (especially brown patch and dollar spot).
If a soil test shows potassium below 150 ppm, apply muriate of potash at 1 to 2 pounds of K2O per 1,000 square feet. Split into two applications (fall and spring) for best results. Retest in 12 months to verify levels have improved.
How to Apply Potash
Use a broadcast spreader for even distribution. Calculate the amount needed based on your soil test recommendation and the K2O percentage of your product. For example, if you need 1 pound of K2O per 1,000 square feet and your muriate of potash is 60 percent K2O, apply 1.67 pounds of product per 1,000 square feet.
Water in with 0.25 to 0.5 inches of irrigation after application. Potassium is water soluble and moves into the root zone quickly. Avoid applying potash to dormant or stressed grass during summer heat.
