How to Reduce Worm Castings In Your Lawn

The following post is excerpted from the May/June 2005 issue of Horticulture


Question:
I’m having a bad problem with worm castings in my lawn. The turf is turning a lumpy, muddy mess. What can I do?

Of the more than 200 species of earthworms in North America, the common night crawler (Lumbricus terrestris) is most likely to be causing your problem. They are a dominant species in temperate regions and play a big role in the breakdown of organic matter and the development of soil.

Night crawlers produce deep vertical underground burrows and feed on organic matter mainly on the soil surface. As they excavate their burrows, these worms consume mineral soil and litter. They excrete their fecal matter, or casts, in mounds on the soil surface. Researchers estimate that earthworms carry 20 to 25 tons of soil per acre up to the surface each year.

The casts actually benefit your lawn, because they contain readily available nutrients. The burrowing activity of the night crawlers and their soil mixing also improve the soil’s drainage, porosity, aeration, and structure. Finally, earthworms decompose thatch and stimulate microbial activity.

However, extraordinarily high populations of night crawlers can produce so many mounds of soil that grass blades are smothered. On sloped ground, the casts can be carried away in heavy rains. Use a rake to scatter the castings across the lawn. If you have an automatic irrigation system, increase the interval between waterings to allow the top few inches of soil to dry out, forcing the earthworms to tunnel deeper into the soil. Also, mow your lawn at the higher end of its recommended height range to hide the castings. An acidifying fertilizer, such as ammonium sulfate, will reduce the soil pH and make it less favorable for night crawlers. However, do not let the pH fall below the 7.0 that is generally needed for the grass to grow well.

Image Credit: Wikimedia Commons

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One thought on “How to Reduce Worm Castings In Your Lawn

  1. OK… maybe it’s just me. The advertising links below this article. The one saying: Mask worm castings with these decorative lawn ornaments.

    How many of these ornaments do you need all over your lawn to hide the castings? Do you put them directly over each mound?

    I know you are trying to sell us stuff, but really, that one suggestion doesn’t seem to fit this subject even remotely. Maybe if you’d worded this item differently… not using the word ‘mask’. How about: Distract attention from worm castings with these decorative Lawn Ornaments.

    If you MUST push advertising on us, please make sure it’s relevant. Even the Related Posts are completely unrelated to the topic of worm castings. I know you want to show us more articles, but why not say what they really are. These are not RELATED. How about just using the words… other posts instead of related posts?

    Don’t know why this bugs me, but it does. Sorry to rant.

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