Pasture grasses need rest to maintain health

By Ernie Marx
Larimer County Extension

Horses are born to roam. Over the hills, through the valleys, across the prairies. The free-spirited, roaming nature of the horse is part of what makes the animal attractive to so many people.

A horse passing through a prairie has little impact. Periodic grazing helps to keep grass healthy. Manure piles scattered about provide nutrients for the soil.

When the animal is confined to a small property, however, everything changes. While some grazing is good for the grass, too much will kill it. A little manure enriches the soil, but too much can cause problems.

When the roam is taken out of the horse, management and land stewardship must be added to the recipe. This is especially true in the semi-arid climate of Larimer County. Grass plants cling to life during hot, dry summers. Added stress, such as overgrazing, can push the plants over the edge.

Leaves are the grass plant's solar energy collectors. The green chlorophyll in the leaves is a factory for converting solar energy into sugars. These sugars are the fuel for plant growth.

The grass plant can tolerate some grazing. In fact, without grazing many grass species could smother themselves with decadent growth.

But too much grazing weakens, and eventually kills, the grass plant. When green leaves are grazed, the plant loses part of its ability to capture the sun's energy. The plant dips into its energy bank account, using reserves to generate new growth. If all goes well, the new leaves will capture enough solar energy to replenish the account.

If the new growth is grazed too soon, however, the plant loses its opportunity to recover. Instead, it must dip once again into reserves. Eventually, those reserves are exhausted and the plant dies.

The grazing behavior of horses makes them especially hard on pastures. Horses prefer to eat the young, soft leaves that regenerate following grazing. They will ignore taller, ungrazed grass plants and graze the new growth on the same plant they grazed last week. With teeth on the front of both their upper and lower jaws (cows don't have front upper teeth), horses can nip the grass down to the ground.

The only way to protect pasture grasses from this type of overgrazing is to remove the animals from the pasture.

A corral is an essential element in a small acreage grazing system. The corral gives the manager a place to keep the horses while the pasture rests. Horses should spend most of their time in the corral. An hour or two of grazing per day is sufficient. During early spring and fall, when grasses are especially sensitive to excessive grazing, animals should spend all of their time in the corral. The horse owner should plan on purchasing feed to meet the nutritional needs of the animal.

Most of the pasture grass species in Larimer County should be 6 to 8 inches tall before grazing begins in the spring. Pastures can be grazed down to a height of about 3 inches. Animals should then be removed while the pasture rests and grass grows back to the original height. Many dryland pastures in Larimer County will need to rest until the next year before they are ready to be grazed again.

In addition to grass height, the number of grazing days must be monitored. To prevent plants from being re-grazed before they have a chance to re-grow, animals should not have access to the same pasture for more than 10 days. After 10 days, move the animals to a different pasture or corral so the plants can recover.

To get more grazing days on a pasture, divide it into cells. An undivided four-acre pasture can support 10 days of grazing before the animals are moved to the corral. That same pasture divided into four one-acre cells, with each cell grazed for 10 days, will allow for 40 days of grazing.

Weeds are one of the first visible signs of overgrazing. The Larimer County Extension office answers dozens of phone calls concerning weeds in pastures. Most often, the weeds are a symptom of a grazing management problem. This is especially true of annual weeds such as mustard, cheatgrass, kochia and Russian thistle. Even bindweed, which doesn't grow well when shaded, will stay under control in a well-managed pasture.

A properly managed pasture will rarely require chemical weed control. If you find yourself battling weeds on a regular basis, restructuring your grazing plan could save you money and work.

To learn more about pasture and grazing management, attend the Small Acreage Workshop on Sept. 9 at the 4-H Building, Larimer County Fairgrounds. Call the CSU-Larimer County Extension Office at 498-6000 for more information or to register.