Warm Season Annuals Make Productive Pastures

PINE BLUFF, Ark. – Warmer, drier conditions are on the way, and this means it is time for ranchers to prepare their pastures, according to David Fernandez, extension livestock specialist and interim dean of graduate studies for the University of Arkansas at Pine Bluff.

To increase the amount of forage on their pastures, ranchers can consider planting warm season annuals, Fernandez said.

Warm season annuals are grasses that grow best when temperatures begin to rise in late spring, he said. Examples include crabgrass, sudangrasses, sorghum-sudangrass hybrids and pearl millet.

“Planting these grasses boosts available forage and gives cool season pastures a rest during the warmer months,” Fernandez said.

Crabgrass is an often overlooked and maligned warm season annual. For ranchers who cut hay, it requires more time to dry than bermudagrass. However, crabgrass is typically much better quality than bermudagrass and other summertime grasses.

Crabgrass can be planted starting when soil temperatures reach 58 degrees F until about mid-June. Crabgrass seed is small and should not be planted more than 1/4 inch deep. Two to 5 pounds per acre should be broadcast on a fine, well-prepared seedbed followed by another pass with the roller to cover it.

Grazing on crabgrass can begin when it is 4 to 6 inches high. For rotational grazing, wait until the grass is 12 inches high. At least 3 to 6 inches of stubble should be left for good regrowth.

Sudangrass is a rapidlygrowing annual that looks like Johnson grass, but is easy to control, Fernandez said. Best production is achieved by fertilizing according to a soil test.

Sudangrass can be drilled or broadcast at a rate of 20 to 30 pounds per acre. Sorghum-sudangrass hybrids should be drilled at a rate of 20 to 30 pounds per acre and broadcast at 30 to 45 pounds per acre.

Soil temperatures should be at least 68 degrees before planting sudangrass.

Grazing on sudangrass or sorghum-sudangrass hybrids can begin when the grasses are about 24 inches tall. For good regrowth, rotate livestock to another pasture when sudangrass is down to 10 to 12 inches and when sorghum-sudangrass is down to 4 to 6 inches.

Fernandez said ranchers who plant sudangrass should keep the following rules in mind:

• Never graze horses on or feed them hay from sudangrass or sorghum-sudangrass pastures because they could develop cystitis syndrome disease.

• Do not harvest or graze drought-damaged sudangrass for at least four to seven days after a good rain to avoid nitrate poisoning in livestock.

• Do not harvest or graze sudangrass after a killing frost to avoid prussic acid poisoning in livestock.

Ranchers can also choose to plant pearl millet. Though the grass does not tolerate cold weather as well as sudangrass and sorghum-sudangrass hybrids, it better tolerates acidic soils and diseases. Also, prussic acid poisoning in livestock is not a problem.

Pearl millet can be drilled at 15 pounds per acre or broadcast at 25 pounds per acre. Grazing on pearl millet can begin when it is 12 to 18 inches tall. Be sure to leave at least 4 to 6 inches of stubble for good regrowth. The grass can be harvested for hay once it reaches 2 to 4 feet tall.