KC Gardens

Despite old wives’ tale, spreading wood ash on your lawn may not be great idea

Most Kansas City-area soils are already naturally high in potassium and pH levels. Adding ash into it means you run the risk of saturating the soil of both.
Most Kansas City-area soils are already naturally high in potassium and pH levels. Adding ash into it means you run the risk of saturating the soil of both. Submitted

When it comes to improving soil, local gardeners are always searching for that magic concoction.

One old wives’ tale is that wood ash makes an excellent soil amendment, helping to make the soil more fertile.

Though ashes do contain significant amounts of potassium or potash, they contain little phosphate and no nitrogen. And that’s why gardeners should beware.

Here is the problem: most local soils are already naturally high in potassium and do not need more. Adding more potassium means you run the risk of saturating the soil.

The result is that the other micronutrients found naturally in the soil and necessary for plant growth become unavailable to plants.

Spreading wood ash on our local soils also raises the pH level. Our soils, for the most part, tend to run on the high side. Adding ashes over time will increase the pH, which will also reduce nutrient availability and result in a decline of growth.

The bottom line is wood ashes add little benefit and may actually harm many local soils. So how do you dispose of the ash without putting it in the trash?

The key is to spread the ash out and dilute their negative properties.

Ash can be added to the compost pile, where it will be defused and continue to break down. Sometimes, the more acidic nature of the compost can offset the additional pH within ash.

A small amount of ash can be lightly broadcasted — or scattered — over the lawn, where the concentration would be lessened. But continued applications to the same area year after year will result in problems with the soil.

For those who burn wood from time to time, broadcasting is the best method of disposal. If you burn a large amount of wood, then you may need to get more creative about where to apply the ash.

A soil test offered through your local county extension office can help reveal the pH of your soil. This will let you know if ash should or should not be applied.

The cost of a soil test varies by each county, but it’s usually provided for a minimal fee. The results provide base-line fertility levels for a healthy lawn and garden.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org.

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