ISU researchers say winter grazing is essential to Iowa’s beef cow-calf production but caution farmers about the possibility of soil erosion as a result of this practice.

“At any point during the winter, erosion risk from pastures is related to rain fall or snow melt intensity, the severity of the slope of the ground and the amount of standing forage and associated decaying vegetation on the soil surface,” said Steve Barnhart, professor of agronomy.

The problem occurs when farmers have cattle on the muddy or soft ground, said Mark Hanna, an agricultural and biosystems engineering scientist.

“This can damage existing forage and other vegetation as well as degrade the stream bank,” he said. “This leads to erosion.”

Hanna said cattle grazing where they have access to a natural body of water also could lead to a problem.

“Hoof traffic degrades the stream bank which becomes a problem in terms of sediment and erosion,” he said. “It could also cause foot and leg injuries to the cattle as they go down to the water and then back up to pasture.”

Though there are problems of erosion associated with winter grazing, Jim Russell, professor of animal science, said ISU Extension researchers still strongly support the practice.

“Winter grazing is a key to improving the profitability of beef cow-calf production in Iowa,” Russell said. “Feeding of stored feeds like hay represents the single largest cost in beef cow-calf production in Iowa.”

Based on six years of research funded by the Leopold Center for Sustainable Agriculture, Russell said decreasing the amount of stored feeds fed to livestock through the use of winter grazing would add up to hay savings of between $88 to $142 per cow.

“The key to successful winter grazing is proper management,” he said.

The first step in proper management is to let the “winter pasture” continue to grow for the remainder of the growing season, ending in mid-November, Barnhart said.

“This will allow the pasture to accumulate a suitable forage mass for animal consumption and for erosion protection,” he said.

Allowing the pasture to grow, Barnhart said, will also prevent the animals from being on the ground before it is frozen.

“Soils are more at risk before freeze-up and again after the soil thaws in the spring,” he said. “This is when soils are less protected by vegetation and more vulnerable to both the impact of raindrops and surface movement of water.”

Once there is proper forage on the pasture, Russell said, it is important not to let the cattle overgraze.

“Overgrazing of the winter forage should be prevented so that adequate forage remains on the pasture to minimize sediment and nutrient loss in water run-off during early spring rains,” he said.

Another alternative is to use stock fields, Hanna said.

“Graze livestock in a corn field where there are leftover stocks from the fall harvest,” he said. “This keeps them in a flatter area with plenty of feed.”

Russell said a farmer could use sacrifice paddocks to prevent erosion as an alternative to the other methods. A sacrifice paddock is where “animals may be placed during muddy periods when pasture soils are susceptible to damage,” he said.

“This approach limits the soil damage to a relatively small area that then can be renovated through reseeding later.”

Farmers also need to have an alternative water source for cattle, Hanna said.

“Cattle traveling up and down a slope to a water source, whether it be a stream or anything else, degrade the stream bank,” he said. “The animals are prone to foot and leg injuries, especially if the ground is not frozen.”

Toxins and other bacteria in the water could be an issue as well, Hanna said.

Winter grazing research was conducted at the McNay Research Farm near Chariton. Russell said researchers, using these management approaches, found no negative effects on soil as a result of winter grazing.

“Some winters, there are virtually no erosion concerns, but the next winter could bring significant mud,” Barnhart said. “The manager must be ready to make mid-winter adjustments to provide for the short-term and long-term sustainability of both the livestock and the pastureland being managed.”