How Much Potash is in Winterizer Fertilizer?

Rates of Potash

• There is no standard amount of potash in a winterizer fertilizer. Different forms of potash are available in winterizer and potassium fertilizers. Some common forms include muriate of potash, which contains 60 percent potassium by volume (0-0-60); potassium sulfate, which contains 50 percent potassium by volume (0-0-50); potassium nitrate, which contains 13 percent nitrogen and 44 percent potassium by volume (13-0-44); and other common formulations such as 5-5-25, containing 5 percent nitrogen, 5 percent phosphorous and 25 percent potassium. Whichever formulation is chosen, actual application rates on turf should not exceed 1 lb. of actual potassium per 1,000 square feet of lawn area.

Precautions

• Too much potash applied to lawns in winterizer fertilizers or at any time of year is harmful to turf. When potash is applied to wet turf, foliar burn can occur. Always apply when the grass is dry and then water the application in. High potassium levels in the soil present competition problems for turf grasses. Nutrients that may be present in the soil in sufficient amounts for healthy turf are not readily absorbed by the roots as the potassium essentially blocks their uptake. This is particularly true for magnesium.

The Debate

• Research and analysis by investigators at Kansas State University and Colorado State University into the role that potassium plays in winterizer fertilizers suggests that they may at best be unnecessary, and at worst, be harmful to the lawn. Cool-season grasses such as fescues and bluegrass do not use very much potassium once established. The recommendations for fall applications on these lawns is to still use fertilizers higher in nitrogen than in potash.

Soil Testing

• The surest way to know how much potassium should be added to your lawn at any time of year is to perform a soil analysis. This can be done with a do-it-yourself kit available at most garden stores, or by sending a sample to your county cooperative extension office. This will reveal the current levels of potassium as well as the pH of your lawn's soil and the current rate of other nutrients. A professional lab analysis will also yield recommendations as to how much fertilizer to apply and when.