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Help pastures withstand drought

Joanna McCarthy/Getty Images Grasslands
DROUGHT SITUATION: Average ranchers will spend 18 years of their life dealing with drought conditions. Range specialist Llewllyn Manske has developed a grazing system to help herds and pastures withstand these conditions.
A North Dakota researcher develops a method that reduces the need to cull cattle and helps grazing land withstand drought.

While ranchers around the region are working with less or lower-quality forages, those who have implemented certain rotational grazing principles might be faring better.

Llewellyn Manske, a range science specialist at North Dakota State University Extension’s Dickinson Research Extension Center, has been researching the biology of grazing systems for over 40 years to develop scientific standards for proper management of grasslands in the Northern Plains.

“The detrimental effects from this drought is not just the lack of water, but also from the lack of mineral nitrogen in the soils,” Manske says.

Producers who run traditional grazing management generally have access to 50 pounds of nitrogen in their rangeland soils, which Manske says is half of what the grass plants need.

Addressing lack of nitrogen

“Intact grassland soils in the Northern Plains have 5 to 6 tons of organic nitrogen, but none of that is available for plants. Pasture soils need a large biomass of microorganism to transform organic nitrogen into mineral nitrogen to make it available for plants,” Manske explains.

This process can be further complicated by the fact that these soil organisms cannot photosynthesize on their own, and require energy.

“What I’ve done in 47 years of research is develop a grazing strategy that uses partial defoliation by grazing cows each year to get the photosynthesized energy from the roots into the soil to feed those soil microbes so they can convert the organic nitrogen to mineral nitrogen,” he says.

Producers who using this strategy have seen the changes made on their range in three years.

“I have 2,000 producers using my system, and no one has called saying they’ve had to cut cows. They’re all at full stocking rates,” Manske says. “Very few years are spent working without water stress.”

On average, a rancher working for 48 years experiences six moderate droughts and two severe droughts. The grassland pastures that have 50 pounds of mineral nitrogen require stock reductions during the eight drought years, plus 10 recovery years.

However, the grassland pastures that have 100 pounds of mineral nitrogen require stock reductions only during the two years of severe drought, plus two years of recovery. The detrimental effects from drought conditions are greatly reduced when grassland ecosystems do not have a nitrogen deficiency and are fully functional.

“These typical guys will work 18 years in a drought or recovering from drought, and only 30 years where they don’t have to work in drought,” he says.

These statistics show producers can reap the benefits of these rotational grazing systems in the long term.

Grazing systems

The rotation system works well with three native rangeland pastures, but up to six pastures can be used.  “It’s a three- to six-pasture system,” Manske says.

Each pasture is grazed for two periods per growing season. He says the first grazing period is 45 days long, from June 1 to July 15. If pastures are similar in size, the three pastures are grazed 15 days each.

“The first period starts after the cool-season lead tillers have produced 3.5 new leaves, and this is the only time of the year that partial defoliation by cattle can move surplus carbon energy from the grass lead tillers and can activate all four primary grass growth mechanisms,” Manske explains.

The days spent in each pasture helps to stimulate the nitrogen production in the soil through the weight of the cattle, and they process of cattle grazing. “After those initial 45 days, we start back over and double the time,” Manske says.

This means that cattle spend 90 days (from July 15 to Oct. 14) in A, B and C pastures, and are able to graze the secondary tillers produced from the first stimulation period that lasted 30 days.

“With the buildup of the soil organisms, we produce aggregation. The aggregation then acts like marbles in a jar, and then we can pour the water around those marbles,” Manske explains, adding that this process is successful due to the grazing cattle pushing surplus photosynthate through the roots, which feeds the soil organisms.

Manske says during the first period, cattle remove 25% to 33% of the weight on 60% to 80% of the grass lead tillers. The soil microbes then increase their biomass and transform organic nitrogen into mineral nitrogen. The lead tillers axillary buds produce vegetative secondary tillers. The other growth mechanisms uptake essential elements and soil water, and produce replacement leaves and stems at 140% of the amount of weight removed by grazing

“Additionally, we have those cattle biting into the grass, which makes the meristem tissues active, which starts pumping that nitrogen and carbon into the plant,” Manske says. “The plants then have that incentive to replace the parts that were removed, which they overcompensate for and produce 140% of the weight that was removed.”

This new growth from the grasses in late July has the same nutritional quality as the grasses grown in June, with 15% to 16% crude protein.

“We’ve been researching this for 36 years straight. No other place in North America has this level of data,” Manske says. “Most people already have three pastures. When we’ve done this out with producers, we’ve torn down more fence than we’ve had to build, but there’s usually no expenses other than changing the systems,” he says.

NDSU Extension also offers an in-person grazing school, held the first week of January. “We are able to set up grazing systems on these three-day workshops, and help producers get started with it,” he says. Check out the NDSU Dickinson Research Extension Center online for more information on attending this grazing school.

 

 

 

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