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Grazing for drought resilience

Monica Gokey for Progressive Cattleman Published on 24 May 2018
Drought year, rotational grazing

Rancher Steve Kenyon moved to Alberta because it was supposed to have more water than the neighboring province of Saskatchewan.

Just a few years after he bought a piece of overgrazed land, the region’s worst drought in 80 years took hold.

“I remember, in 2002, the highways were thick with grasshoppers,” Kenyon says. “Not just squished grasshoppers, but the grasshoppers were hopping up onto cars and clogging their radiators. Cars were overheating everywhere.”

Those same grasshoppers also did a number on Kenyon’s grass. He was relatively new to intensive rotational grazing at that point, but Kenyon had his system set up. It had been in place for a couple of years by the time drought hit.

Health-wise, his pastures were still a far cry from what he was working toward. “The land was severely overgrazed when I got it,” he says. “I hadn’t fixed the land yet.”

To his surprise, the land fared better than expected during the two-year drought. When drought relief finally came in the form of a 3- to 4-inch rain, Kenyon was as excited as his neighbors. Then he noticed their stockwater ponds swelling with water while his stayed empty. “I was disappointed,” he recalls.

Kenyon’s stockwater ponds didn’t finally fill until two weeks after the rain. But when they filled, they overflowed. He immediately realized what had happened: In the few short years he was managing grazing for soil health, it had worked.

When the big rain came, it soaked into the thatch layer on top of his soil instead of running off straight into a stockwater pond. In other words, Kenyon managed to keep that rainwater on the land longer – which is exactly what his rotational grazing system was supposed to do to improve the land’s water cycle.

alberta rancher Steve Kenyon's pastures yielded strong clover and forage stands

Since that first drought, Kenyon has put drought planning at the forefront of his grazing system. “You’ve got to plan for a drought 10 years before it hits,” he says. “In 2002, I only had a couple years. I had only just started to build my thatch layer, my water-holding capacity.”

Kenyon likens drought planning to a bank account. In nondrought years, it pays to leave added plant residue on the ground – those are deposits into your soil’s bank account. If producers leave, or “deposit,” what organic matter they can afford to, they can withdraw on that during the drought, Kenyon says.

He points out long-term pasture health depends on feeding three systems: cows (of course) but also the soil’s microbial community and the soil itself. Leaving grass for the latter two pays off in drought years, chiefly by helping to curb evaporation and runoff.

The next part of Kenyon’s drought grazing philosophy may seem counterintuitive: He grazes his pastures longer, with the caveat they get a longer rest period during dry spells.

“When you’re in a drought, what you need to do is protect the root systems,” he says. “The health of a plant depends on preserving the root system. They’ll replenish their root stores at a slower rate during drought, so those plants need a longer rest period.”

If he’s left enough residue during the nondrought years, Kenyon says he doesn’t hesitate to graze off more green matter than usual in a dry year – that’s where the longer grazing period comes into play. It’s his “withdrawal” from his soil’s bank account.

University of Nebraska Extension Forage Specialist Bruce Anderson echoes Kenyon’s philosophy that a healthy root base is key to drought-resilient pastures.

“One of the best ways to have plants resilient to drought is having plants with deep, robust, aggressive root systems,” Anderson says. “That only happens when we give plants adequate time after grazing to reach an adequate growth stage before they’re defoliated again.”

Healthy root systems also give plants a larger volume of soil to absorb moisture from, Anderson says. The difference can be as stark as a 5- to 6-foot root reach in the soil versus just 1 to 2 feet in less healthy root systems.

But before zooming in on what exactly happens to plants during drought, it helps to look at their life cycle from the 30,000-foot view. Starting in the spring, warming temperatures are a plant’s cue the growing season is here.

“Most important for those growing plants will be taking in moisture, along with some of the nutrients stored over the winter in the root and crown system,” Anderson says. With those two inputs, plants will start metabolizing energy to grow new leaves so they can gather more light, enabling more photosynthesis, which enables more growth.

Now, let’s add drought into the mix.

“Whenever we get to the point where there’s insufficient moisture available in the soil for the plant to keep growing at its potential growth rate, we’ll see the plant slow its growth,” Anderson says. Slower growth is a plant’s defense mechanism when water is scarce. It’s in the plant’s best interest to preserve its energy and nutrient stores for more favorable growing conditions.

The arrival of moisture cues plants to start growing again, and plants will tap into their stored nutrient reserves to initiate that growth.

“Eventually, that new growth will be able to carry on enough photosynthesis to start replacing the nutrients used to get it started. But if we remove leaf area (by grazing) before those nutrients have been replaced by the plant, we then have plants which need to go through that whole regrowth process again, but they’re starting from a lower point, nutrient-wise,” Anderson says.

Over time, depleting a plant’s nutrient stores compromises survival. “A short-term drought influences productivity during that time, but rarely does it result in loss of plants, loss of stands, loss of long-term growth potential,” Anderson says. “But when you start getting in to multiyear droughts, it becomes very difficult for plants to build up nutrients in their root system and use them to maintain some growth. Eventually, they exhaust what they have and perish.”

Anderson sees producers get in a pickle after fresh green-up, when rains finally break a dry spell. It can be tempting to graze new growth right away, but allowing plants a head start on growth that will replenish their nutrient stores is in the best interest of the plant’s long-term health. Anderson’s rule of thumb is to hold off on grazing until a plant has developed three or four full leaves, which he points to as a sign of good recovery from drought.

For cattle ranchers like Steve Kenyon, it’s not a question of if drought is on the horizon, but when. In his eyes, a rancher’s best defense against drought is healthy soil and healthy forage plants, built up through years of healthy grazing management.  end mark

PHOTO 1: This photo was taken in October 2015, a drought year in Alberta. Rancher Steve Kenyon was grazing long after his neighbors stopped. He says rotational grazing is what kept his pastures and soil healthy, even during drought.

PHOTO 2: Alberta rancher Steve Kenyon’s pastures yielded strong clover and forage stands despite a drought during the summer of 2015. He was able to graze well into the fall, despite the dry year. Photos by Steve Kenyon.

Monica Gokey is a freelancer and livestock producer based in Idaho.

Predicting drought

Although drought is somewhat cyclical in parts of North America, predicting drought is far from an exact science. The Climate Prediction Center (CPC) offers a monthly and seasonal drought outlook. The prediction models used to inform CPC reports look to large-scale climate patterns, like El Nino, to infer probable temperature and moisture conditions.

The other major resource producers look to for drought information is the U.S. Drought Monitor. University of Nebraska climate scientist Deborah Bathke is one of the authors of the U.S. Drought Monitor report, which is updated weekly.

“Part of the reason for having the Drought Monitor is for early warning,” Bathke says. “Every week someone is looking at those conditions and starting to see when it dries out.”