Successful pasture management is both art and science
As both a sheep producer and an animal scientist for the USDA-ARS Pasture Systems and Watershed Management Research Unit, Kathy Soder understands the balances and trade-offs that exist between animal production and maintaining good pastures.
"Sometimes we tend to focus on the animals and forget to worry about the pasture," she pointed out in a presentation Saturday at the Wisconsin Sheep & Wool Festival here.
Soder favors rotational grazing practices, with producers allowing sheep to graze on pastures for short durations, with adequate rests between grazing periods.
While 10 inches of grass is the desired goal before sheep are let into a paddock, many pastures are overgrazed and look like exercise lots.
A high percentage of pastures also suffer from poor or uneven fertility, she said.
Soder said grass stems act like solar panels. When grass is grazed too short, weeds are good at filling in the gaps between plants, crowding out grass rhizomes that otherwise would do that job.
Cool-season grasses should be grazed only until two-four inches of plants are left in a paddock, she explained. This strategy leaves grasses with a metabolic reserve, allowing them to recover and grow more quickly.
Pasture grasses grazed down to the ground have the slowest regrowth rate, while grasses grazed down to three to ten inches have the fastest regrowth rate.
On the other end of the spectrum, producers should avoid allowing grass to produce seed heads, and when paddocks are approaching that point, it's an opportunity to mechanically harvest grass and stockpile it for the winter months.
Healthy grass roots can stretch two-eight feet into the soil, and those roots aerate the soil, bring moisture to the plant, provide soil organic matter and provide passageways for water filtration after rainfall.
Research shows that when plants are clipped every week for three months, the extensive root system dwindles, and plants can die during dry periods.
Length of grazing
Soder said that for rapid regrowth of pastures, sheep producers need to ascribe to the "take half, leave half" practice when it comes to moving sheep to a new paddock. As a sheep producer, though, she knows that's easier said than done.
A good rule of thumb is that, at the point where producers question whether they could graze a paddock for one more day, it's best to move the sheep to a new paddock.
Depending on the size of the paddock, three days is often the maximum time a flock should spend in any one paddock.
"It's hard to do. . . but it's an investment," she said. "... You're investing in the next grazing cycle. What you leave behind assists the regrowth rate, root growth, soil temperature, organic matter, water infiltration rate, water-holding capacity and nutrient cycling."
There is no uniform rule about how long sheep should graze a paddock and how quickly animals can return to the paddock.
"It depends" on a lot of considerations, including the amount of forage available, the size of the paddocks, the estimated seasonal growth, sheep numbers and the nutritional needs of the sheep, Soder said.
"There is an art and science to rotational grazing," she explained. ". . . The art of grazing management is to ensure that there's sufficient pasture in a stage suitable to graze at all times through the grazing season."
Rotational grazing is especially well suited to sheep because parasite eggs can hatch while sheep are in another paddock and are not ingested.
Soder said she and her husband often are providing paddocks with a four-six-week resting period between grazing, and they are seeing a difference in the parasite load of their flock.
For those getting started with rotational grazing for sheep, Soder said the first requirement is a good perimeter fence.
From there, producers should use temporary fencing and consider establishing five-10 paddocks that are grazed rotationally
A grazing period of three-seven days will provide paddocks with 25-30 days of rest between grazings.
Producers don't need a fancy watering system; a truck with tanks can deliver water to paddocks until producers determine what paddock configuration works best for them. When it comes to interior fences, Soder pointed out that no fence is predator-proof, but it takes three-five days for predators to figure out a new fence configuration.
Forage quality and quantity will vary as the growing season advances, and a good rule of thumb is "if you're not mowing your lawn, your pasture isn't growing either. Over 80°F, your pasture doesn't grow very much," Soder said.
Cool-season grasses will experience their greatest growth in May and June, with a second flush of growth in the fall.
Warm-season grasses have their maximum growth during mid-summer.
These forage legumes have deeper root systems and will have more consistent growth during the entire growing season, so having a mix of warm- and cool-season grasses in pastures can sometimes carry producers through a summer slow-down without overgrazing.
Even with such a mix, at this time of year in particular, producers might need to delay putting sheep back into paddocks for 40 or more days.
This could mean that producers need to have a sacrifice or dry lot, when sheep are fed dry hay while pastures recover from grazing.
There are different approaches available for pasture renovation. When Soder and her husband moved to their farm, there was enough wire and debris in the tall weeds that they knew they couldn't start the process by mowing. They allowed their sheep to "mow" the grass and weeds, knowing they would sacrifice their first wool clip due to the large crop of burdock in the pastures.
After the weeds were eaten down and debris removed, paddocks were established and mowing weeds and grazing were their method of building good pastures.
Soder recommends producers have soils tested, as lime may be needed to ensure good nutrient levels.
If producers are tilling cropland to establish pastures, controlling weed growth is vital, whether that is done by agrichemical use or hand weeding.
In established pastures, over-grazing is an option to initially control weeds.
If producers want to over-seed an existing pasture, Soder recommends they "graze hard" to remove weed competition, and reseed by broadcasting or no-tilling.
Seed-to-soil contact is important, and sheep hooves do a good job of pushing the seed into the soil immediately after over-seeding.
After grass starts to grow, it's best to remove the sheep and allow the stand to become established before grazing heavily as sheep can pull new grass out by the roots.
As grass gets established, it may need a rescue treatment to prevent weeds from crowding out new grass, and grazing by another species, agrichemical application or hand-weeding are options.
Soder concluded by saying successful pasture systems are simple yet flexible, combine permanent and temporary fences, keep plant growth vegetative, and have fencing that follows the landscape to make paddocks,
Successful pasture systems also use animal flow patterns for determining placement of gates and fences, balance forage productivity with animal productivity, use forage and soil testing, include legumes to fix nitrogen, require producers to be flexible in their management, rely on paddocks being grazed quickly and getting adequate rest between grazing periods, and depend on producers ensuring enough leaf area remains after grazing that grasses can serve as solar panels.
When producers successfully manage their pastures, they not only have quality pastures but also the carrying capacity of their pastures often is double that of over-grazed lots.