March 3, 2000 | By: Mark Eclov

The early part of the new year brought icy conditions to many Midwestern sidewalks and driveways. One recommendation making the rounds again suggests using lawn or garden fertilizer as a substitute for normal salt de-icers.

"That idea has probably been around ever since someone discovered that fertilizers are basically soluble salts and that they interact with ice and change it's freezing point and cause it to melt," said John Grove, agronomy professor in the UK College of Agriculture.

"The biggest problem of using fertilizer salts as a de-icer is that you have to think about where the water is going," said Grove.

When water travels in most urban areas, it enters a storm sewer or drain system and the fertilizer nutrients leave with the water. In other cases, this salty water travels to the edge of the sidewalk and may eventually provide some nutrients to grass and shrubs located near the edge of the sidewalk, but typically most of the water ends up somewhere other than the yard.

"The second issue is the amount of salt in the water," noted Grove. "All fertilizers have the capability of becoming too salty before they provide nutrients and too much salt can result in dead spots in the lawn."

The third issue is timing. If fertilizers are used as de-icers anytime up until mid-winter, they usually are of little benefit to the lawn because the nitrate part of the ammonium nitrate could be long gone before it can benefit the grass.

"The phosphorus and potassium will stick around, but again they tend to stay localized around the edge of the sidewalk," added Grove. And do you need these extra nutrients? Chances are if you have a maintenance program already in place, this part of your lawn will not benefit at all from the added fertilizer.

There also is more than a little testimonial evidence that suggests the continual use of significant amounts of fertilizer actually may hurt the pavement.

"I do not know all the chemistry associated with the process, but over time, ammonium nitrate fertilizer in particular is known to react with concrete and can cause the upper surface of the concrete to lose that troweled-off look," said Grove. "You can end up with your first layer of aggregate exposed."

Another bottom line issue is cost. Typically speaking, most fertilizers are significantly more expensive than common de-icing salt.

"Anyone who is still tempted to try fertilizer as a de-icing salt substitute should consider using potash," suggested. "It is the cheapest of the fertilizer formulations and is effective as a de-icer."

Grove specifically recommended muriate of potash. Many tobacco producers have sulfate of potash available on the farm, but it's not going to be as effective. Muriate of potash is also about half the cost of sulfate of potash.

"This formulation is normally found at farm supply stores or some large lawn and garden centers and would be labeled as an 0-0-60 formulation," said Grove.

Grove recommended any homeowner with fertilizer questions should check with their local county Cooperative Extension Service agent for agriculture.


John Grove 606-257-5852