Remember the R’s: Roots Key to Resilience

For Tri-State Livestock News, sixth in a 6-part online series763 words main story, 114 words sidebar

Remember the R’s: Roots Key to Resilience

There’s a grazing line you shouldn’t cross to keep roots healthy

By Lynn Betts

There’s a reason soil health specialists recommend you take a spade with you when you take a look at your pastures. The first reason is to see whether your soil has pore spaces that rapidly infiltrate and store rainwaters, or if it is compacted with a platy structure which slows water infiltration.

But an equally important reason is to take a close look at the root systems. That’s because the grass you see—or don’t see—above ground is directly reflected in the supporting root system below ground. Generally speaking, in healthy grasslands, the amount of biomass below ground is much greater than that above ground.

An important grazing fact many people don’t know is that in most years, about one-half of a grass plant’s roots die naturally. They have to be replaced by new roots; the speed and amount of new root growth is directly affected by how much of the plant’s leaf volume has been removed. Go too far—graze too close and remove too much top growth—and the roots aren’t replaced at all and the plant will eventually die.

The line you don’t want to cross

“If you move livestock out to leave about half the grass volume in a pasture—that usually means leaving at least 4 inches of grass height after grazing—root growth is largely unaffected and plants regrow fairly rapidly,” says Tanse Herrmann, grazing lands soil health specialist for the USDA Natural Resources Conservation Service in South Dakota. “Research shows when you leave 50 percent by weight (4 inches or more residual grass), less than 5 percent of the roots stop growing. But if you go just a little beyond that, and remove 60 percent of the top growth, you stop 50 percent of root growth. And if you remove 70 percent of the plant, you stop nearly 80 percent of root growth.”

“The line you don’t want to cross—unless you intentionally want to reduce a grass like bluegrass in a pasture, is that 50 percent mark. That’s where the take half, leave half saying comes from,” Herrmann says. Note: season of grazing use if attempting to reduce invader species is critical. Consult with NRCS for strategic guidance.

Roots key to water availability, soil health

“Capturing and holding water, and delivering nutrients to plants are maybe the most important things you can do to get productive grasslands,” Herrmann continues, “and healthy plant root systems make that happen. When you rotate pastures to allow enough leaf surface to capture sunlight and pump energy to the plant roots, those actively growing roots put out sugars and other root exudates that feed microbes in the soil. Those microbes and other soil biology make the glue that binds the soil together, forming soil aggregates with pore space that promotes infiltration and water holding capacity. Growing roots are crucial to developing healthy soils that absorb and hold water.”

“And guess what else?” Herrmann continues. “Plant parts are made of carbon. More residual grass left in your pastures after grazing means more robust root systems. Excellent grassland managers are growing carbon – organic matter – for continued resilience of grassland resources.”

Drought-proofing the farm

“We went all no-till almost 30 years ago, and started planting cover crops and more intensive rotational grazing here in the last five years,” says Candice Olson-Mizera of McLaughlin, South Dakota. She farms and grazes about 600 head of Angus cross cattle with her husband Bob and niece Kaydra Jaragoske, with more help from two hired men and her father.

“We’ve really intensified our rotational grazing and use of cover crops. We get anywhere from 15 to 17 inches of rainfall a year on average. What we’re striving for is to insulate ourselves and capture and hold as much of that moisture as possible for further growth. We’re just trying to drought-proof the farm, is what we’re trying to do, improving the water infiltration and the holding capacity.”

“We have the cows graze in a smaller area, so the rest of the pastures have all got time to grow. That’s made a huge difference,” Olson-Mizera says. “It’s just improved our lives in so many different ways, with time management and efficiencies and profitability.”

Olson-Mizera says leaving residue to insulate and protect the soil and having growing, diverse roots are among the best and fastest ways to improve soil health and rangeland productivity. She warns that underuse of grasses can be detrimental to rangeland health, and also believes tall grass and a healthy ecosystem is the best defense against invader species like Kentucky bluegrass, as well as prairie dogs.

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Suggested sidebar:

Series recap in a nutshell: Why Ranchers should Remember the R’s

Rotating pastures is the grazing management technique that enables pastures to be rested. This period of Rest after grazing, in turn, allows time for both plants and their roots to Recover. This recovery time, when enough moisture and other favorable conditions allow regrowth, promotes natural diversity in grasslands. Optimum stocking Rate matches the amount of expected forage to numbers of livestock, helping ensure grasses will not be overgrazed. Giving plant Roots time to recover after grazing is critical to long-term plant health, as well as to feeding soil microbes that build healthy soils able to infiltrate and hold rainfall. Keep the R’s in mind to set the framework for resilient soils, grasslands, and ranches.

Editor’s note: Sixth in a 6-part series recommending ranchers break down grazing management principles to memorable “R” actions that lead to resilient grazinglands on South Dakota farms and ranches.