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Grazing Too Short in Fall and Winter Can Mean More Weeds in the Spring

By   /  October 1, 2018  /  No Comments

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Back in September of 2016, On Pasture readers were wondering if their fall and winter grazing might have an impact on the health of their pastures come spring. Turns out, it’s always a good idea to leave enough grass so you don’t add to your spring weed problems.

Results of a study by University of Wisconsin-Madison researchers show that if you graze shorter you’re helping weed seeds get the light and resources they need to germinate well in the spring. Their study focused on burdock, but results could be similar for other weed species that germinate in early spring.

Photo courtesy of Wikipedia

Photo courtesy of Wikipedia

Agroecology Researcher Mark Renz and Marie Schmidt hypothesized that fewer burdocks would be established where more residual grass blocked sunlight from reaching the ground in March through early April when burdocks and other weeds begin growing. To test their idea, they clipped pasture plots to mimic grazing to five different heights: two inches, four inches, six inches, eight inches and unclipped. This November clipping was timed so it was as similar as possible to managed grazing pastures nearby.

Since burdock needs light to germinate, Renz and Schmidt went back to their plots in April to measure the amount of light being intercepted by foliage. As you’d guess, the shorter the foliage, the more light made it to the ground. The plots grazed to two and four inches at the Arlington farm intercepted 41% less light than the six and eight inch plots. At the Franbrook Farm the four inch plots intercepted 34% less light than the six and eight inch, and unclipped plots.

Though the differences in how much light was being intercepted diminished as the grass grew into May, the damage was already done. There was more burdock in the plots that were clipped shorter. At the Arlington Farm, researchers found that when only 30 percent of the light was intercepted, as it was in the two and four inch clipped plots, they could predict .46 burdock plants per square foot, or 20,000 per acre. With residual of 6 to 8 inches, 75 percent of the light was intercepted for .17 burdock per square foot or only about 7400 per acre.

It’s important to note that the researchers found differences in their plots between the two farms. Franbrook started with lower weed densities than the Arlington Farm, and also had a greater diversity of pasture plants. Overall there were fewer burdock at Franbrook, even in plots clipped to two and four inches.

What Can You Expect?

Renz and Schmidt’s study shows that retaining a six to eight inch residual height through the fall and into the start of the next grazing season can reduce burdock establishment by an average of 82 percent. They expect that other biennial pasture weeds such as bull thistle and common mullein may react similarly. They  also pointed out that your results may vary because animals don’t graze each plant to the exact same height, and some may even graze burdock.

biennial-weeds-list

Can’t Beat It? Eat It!

A dish containing a Japanese appetizer, kinpira gobō, consisting of sautéed burdock root and carrot, with a side of sautéed dried daikon. Photo courtesy of Wikipedia

A dish containing a Japanese appetizer, kinpira gobō, consisting of sautéed burdock root and carrot, with a side of sautéed dried daikon. Photo courtesy of Wikipedia

Burdock is actually a quite palatable weed, high in nutritional value for both livestock and humans. While it’s fallen out of favor in European cuisine, the taproot is still harvested and eaten as a vegetable in Japan. Cut the stalks before they flower, peel them and boil them in water and you have a vegetable that tastes like an artichoke (to which burdock is related).

Let us know how your grazing goes, both by livestock  and in your own kitchen!

Hey! A Big Thanks to the On Pasture supporters providing financial support. You make On Pasture happen every week! To be sustainable, we need community-wide support. If it’s an option for you, consider becoming an “Ongoing Supporter” at just $5/month. Being able to show that kind of support is especially helpful when we’re approaching outside funders.

Thanks to the National Grazing Lands Coalition for making this article possible.

NatGLC’s The 7th National Grazing Lands Conference is coming up in December 2 – 5 in Reno. It’s one of On Pasture’s favorites because folks just like you are the speakers, sharing their great experiences. Register before October 16 to get the best price. It’s just $395 for you and you can bring a friend or spouse for $175 more. On Pasture will be there. Come see us!

 

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About the author

Publisher, Editor and Author

Kathy worked with the Bureau of Land Management for 12 years before founding Livestock for Landscapes in 2004. Her twelve years at the agency allowed her to pursue her goal of helping communities find ways to live profitably AND sustainably in their environment. She has been researching and working with livestock as a land management tool for over a decade. When she's not helping farmers, ranchers and land managers on-site, she writes articles, and books, and edits videos to help others turn their livestock into landscape managers.

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