If you allow animals to graze more than 60% of the plant leaf volume of pasture plants, you’ll stop 80% to 100% of root growth.

If you move grazing animals to the next paddock when 40% to 50% of the total leaf volume of plants is consumed, you will lose only 5% of root growth. Such prescription grazing can help current species thrive.

However, does this common prescription of “take half, leave half” reduce cool-season invasive species like Kentucky bluegrass, smooth brome or crested wheatgrass?

The short answer: not everywhere. Prescriptive grazing can increase invasive species. However, ranchers are learning that by shifting to smaller paddock adaptive management — where daily observation replaces grazing formulas — soil health will improve, and more native species will emerge given time.

Moving away from prescriptions

For decades, Mobridge, S.D., rancher Justin Thompson thought he was doing everything right. He practiced the take-half-leave-half prescription to maintain two ranches and build grass reserves for the dry years he had experienced on his ranch with sandy soils in the late 1990s into the early 2000s.

“We were rolling along for 18 to 20 years, adding fencing and water, changing cattle numbers and rotations, and improving continually, thanks to incentive programs, rangeland school advice, and longtime mentors like Ryan Beer” with the Natural Resources Conservation Service in South Dakota, Thompson says.

Unfortunately, the healthy and diverse species of western wheat and green needlegrass that thrived on the Thompson’s ranch with sandy soils were losing out to invasive species on his other ranch with clay soils. Both soil types were managed the same.

Stockpiling grass led to some pastures being left ungrazed, followed by heavy snows in 2018 and 2019. In the clay soils, waist to shoulder-high yellow sweet clover took over, reducing grazing and leading to Kentucky bluegrass developing thick mats.

In 2018 on his clay soils, Thompson noticed increasing smooth brome and crested wheatgrass coming in near ditches, ridges, creeks and any spot where seed could move in. “It started to take over, but the Kentucky bluegrass bothered me the most,” he says.

Thompson says 2022 seemed to grow an exceptional amount of bluegrass, which took over pastures quickly. Early rains helped the shallow-rooted Kentucky bluegrass flourish.

What worked on his ranch with sandy soils 20 miles away had the opposite effect on his ranch with clay soils. “I realized that if I continued managing both ranches the same, the clay ranch would be nothing but brome, bluegrass and crested wheatgrass,” Thompson says.

Hoof action aids native grasses

As adaptive grazing pros will tell you, the rule of disruption is one of three fundamental principles for success. Thompson witnessed such transformation in a cow-trampled alleyway as cows searched for their newly weaned calves. This 12- to 13-day weaning event in late October occurred next to an untouched hay corral three years in a row.

MAKING A DIFFERENCE: Ryan Beer with NRCS helps producers continually improve pasture conditions. (Barret Self)

After intense, short-lived hoof trampling, followed by long rests, the power of observation kicked in for Thompson and NRCS’s Beer.

“This disturbance created an amazing opportunity for western wheatgrass to grow and replace the invasive species. It was a night-and-day difference across the fence in the untrampled and not grazed hay corral, where Kentucky bluegrass and its thick mat of dead residue continued to thrive by not allowing native grasses to grow,” Thompson says.

Other soil disturbance events at Thompson’s ranch allowed western wheatgrass tillers to emerge as intense hoof traffic destroyed the Kentucky bluegrass mat:

Beer says not adapting to conditions is a problem he sees across South and North Dakota. “It stems from trying to do a one-size-fits-all grazing system, instead of adapting to different conditions with specific actions,” he says. “Sometimes, we need to do more, take more than half; then let it rest and recover. The buffalo were out on the range in April and May. Why shouldn’t our cattle, too?”

Beer says leaving too much grass, especially with the thatch buildup that bluegrass causes, repels native grasses and rain infiltration. “Drought can help knock Kentucky bluegrass back, but the wet 2022 spring brought it back with a vengeance. It just takes time to bring back the native grasses,” he adds.

Adapt for more hoof traffic

Hoof action causing the reemergence of native grasses now has Thompson trying a higher density of animals by fence-line weaning the calves and then winter grazing, with rotations starting in November. As weather permits, the yearlings stay in pastures until September shipping.

With extra yearlings and dividing paddocks in half, Thompson is using them as tools rather than increasing cow numbers.

“Adding fence, water lines and tanks while doubling our rotation is improving our adaptive management,” Thompson says. “We even tried a one-time event of cutting hay to remove some bluegrass thatch areas to encourage grazing. But every year is different, and every ranch has its own challenges.”

Thompson is committed to trying different steps because he knows the ranch’s livelihood connects to how well they manage the land and resources. “There are no cut-and-dried answers, but I have the responsibility to improve and do the best I can while raising a family with this livelihood,” he says.

Without a focus on continuous keen observation, adaptive grazing cannot reach goals like reduced invasive species, soil aggregate and carbon improvements, and better root growth.

Watch consequences, timing

Beer says producers should consider some unintended consequences of early hard grazing to reduce bluegrass, which can also reduce some production of western wheatgrass. “Fortunately, producers won’t choose this tactic on the same piece of ground every year, and paddocks rebound better a year after a hard graze with more natives and more overall production,” he says.

Allen Williams, an adaptive grazing management practitioner, consultant and former academic, says timing by species is critical when using ultra-high stock density grazing. “For example, with invasive species like fescue, cheatgrass and smooth brome, producers must wait past the boot stage before hard grazing. Otherwise, you encourage more of these species.”

As Williams will attest in his podcast, Adaptive Grazing Masterclass, adaptive grazing doesn’t rely on a prescription or formula. It is steeped in observation and constant adjustment. He also describes how the daily observation time invested is often less labor-intensive than feeding hay all winter.

Williams’ two decades of adaptive grazing and regenerative agriculture work have proven successful by implementing the practice in every scenario and environment globally. He is one of the four founding partners of Understanding Ag, which promotes regenerative agriculture.

3 rules of adaptive stewardship

At Understanding Ag, Williams says they teach three rules:

1. Rule of Compounding. Nature and biology create compounding or cascading positive or negative effects. Avoid the negative.

2. Rule of Diversity. Boost diversity in everything from microbes beneath the soil to plant species, insects, birds and other wildlife.

3. Rule of Disruption. This is the critical core to being truly adaptive in a grazing practice. Planned, purposeful disruptions to challenge nature in different areas at different times of the year lead to incremental growth toward goals.

“I’ve never been more passionate and excited about agriculture now because of adaptive stewardship,” Williams says. “Good observation creates a keen intuition that makes producers far better decision makers.”

To learn more details about Thompson’s continuing journey to bring back more native grasses, listen to the podcast S.D. Rancher’s Unique Approach to Manage Cool-season Invasives.