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Two Grasses Show Us Why Grazing Management is Both an Art and a Science

By   /  July 6, 2020  /  1 Comment

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Different grasses respond differently to grazing. Knowing what those responses are might change how we manage our pastures to get maximum productivity. From July of 2016, here’s some food for thought.

How is grass productivity above and below ground affected by grazing at different heights or by leaving different residuals after grazing? A study at UW-Madison found no simple answer to this question. Productivity of pasture grasses varies across grazing management strategies and species.

The Study

Want more study details? Click here.

Want more study details? Click here.

Nadia Alber with the UW-Madison Nelson Institute for Environmental Studies experimented with grazing management of different cool season grass species at the U.S. Dairy Forage Research Center farm near Prairie du Sac, Wisconsin. She grazed 1,000 pound Holstein heifers on paddocks where half were seeded with ‘Bartura’ meadow fescue, and half with ‘Bronc’ orchardgrass. Grazing began when the grass was either 12 inches tall or 24 inches tall and continued from April to October in 2009 and 2010. The heifers grazed off either 50% or down to 1.5 inches of stubble (100%). Alber measured above- and below-ground production using a rising plate meter and root cores.

What Happened

There’s a lot of information packed into the two graphs below showing what happened to above- and below-ground production for the two different grasses in 2009 and 2010. First, you can see that production was affected by rainfall. Production was much lower in 2009, with 26.5 inches of rainfall than in 2010 when there was 40 inches of rainfall. The exception was that in the drier year (2009) meadow fescue below-ground production increased when grazing started when the grass was 12 inches high and then grazed down to stubble (100%). Alber can’t explain why this might have happened. Another unexpected result was that in the drier year (2009), both grasses produced greater above-ground biomass with 100 percent grazing at both 12- and 24-inch grazing heights than with 50 percent grazing. Of course, this results in longer recovery times, and given what we know about long-term over-grazing, this probably isn’t sustainable.

The graphs also show that the below-ground production of orchardgrass remained relatively constant regardless of how it was grazed, but meadow fescue showed increased below-ground production when grazed at 24 inches in 2010. This was true at both the 50 and 100 percent defoliation levels, indicating that these two grasses have different potentials for storing carbon in the soil. Alber hypothesizes that the structure of orchardgrass allows it to maintain photosynthesis and a level of carbon supply sufficient to support growth without depleting below-ground carbon, unlike meadow fescue, but more research is needed to test her theory.

Alber study graphs

Take Home Message

The differences shown between just these two species demonstrate once again that there is no such thing as a simple, cookbook approach to grazing that will maximize production above- and below-ground for all cool-season grasses. While it’s complicated to try and manage when you have multiple species, don’t let that convince you to go mono-culture. Different species provide different benefits. Here meadow fescue provides more root mass, which is good for feeding our soil, while orchard grass provided more forage, which is good for feeding our livestock. Feeding both is critical to our success.

Thanks to the National Grazing Lands Coalition for making this article possible. Click on over to see the great work they do for all of us. Thank them for supporting On Pasture by liking their facebook page.

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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.

1 Comment

  1. Tim Gieseke says:

    So, the tall-to-short program worked in the 2-year study, but you mention that “Of course, this results in longer recovery times, and given what we know about long-term over-grazing, this probably isn’t sustainable.” I have leaned a bit more toward the tall-to-shorter strategy the last couple of years. I like that I am growing a bigger root and don’t mind giving up that root-pruned carbon to the soil. With our 14 paddocks, it does give each paddock ~ another two weeks of rest after it was taken down low. Of course, weather has an influence on my decisions.

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