Using Wood Ash in the Garden

Reader Contribution by Vicki Mattern
Published on February 21, 2013
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We’ve accumulated a lot of wood ash over the winter. Can we add it to our garden soil or compost pile?

Whether using wood ash in the garden is a good idea depends on your garden soil’s pH and fertility levels. If a soil test has shown your garden soil’s pH to be below 6.0 (meaning it’s moderately acidic), adding wood ash could be beneficial, says Garn Wallace, who holds a doctorate in biochemistry and is general manager of Wallace Laboratories in El Segundo, Calif.

In acidic soils, wood ash can increase soil fertility by increasing the availability of phosphorus and potassium as well as some micronutrients — although wood ashes won’t supply any nitrogen. Also rich in calcium, wood ashes are effective for raising soil pH — a potential benefit in places where pH is below the ideal level for most vegetables (6.0 to 7.0).

“Moderation is the key,” Wallace says. “People tend to over-apply nutrients. And after you add something to the soil, you can’t take it away without replacing the soil. If you apply wood ashes without a soil test, it is possible to ruin soil in just one year.”

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