Potassium (K)
The third number in an NPK ratio. Potassium strengthens grass cell walls, improves drought and cold tolerance, and boosts disease resistance. It is the key ingredient in "winterizer" fertilizers applied in fall.
Potassium (K) is sometimes called the "stress nutrient" because it helps grass withstand environmental pressure — drought, cold, heat, disease, and foot traffic. It does not drive visible growth or color the way nitrogen does, but it makes the plant tougher overall.
Fall application: High-potassium fertilizers (winterizers) applied in fall help grass store energy and harden cell walls before winter. This leads to stronger spring green-up.
Sources: Potassium in fertilizers usually comes from muriate of potash (0-0-60) or sulfate of potash (0-0-50). Both are effective.
More on Fertilizer
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