A blackened pasture warms faster on a cold spring day. That starts early grass growth.
“Fire is the most underused grass management tool we have,” says Rob Kallenbach, University of Missouri Extension forage specialist.
With the long, cold winter followed by a delayed spring, fire may offer a chance to jump-start grass growth by warming the soil.
“We know the value of controlled burns on native warm-season grasses. But we don’t realize the value of fire on cool-season grass.”
“We are talking wise use of fire,” Kallenbach says. “It’s called a controlled burn for a reason. It takes preparation, a crew, tools, water tank and a tractor with a tillage tool on standby at the burn site.”
Burning a pasture isn't a light-it-and-leave-it method. “Fire must be watched and controlled. It’s not something you do when winds are 30 miles per hour.”
Burning cool-season grass pastures comes earlier in the year than burning a native-prairie pasture. But benefits are similar.
The fire removes thatch that shades new growth. And minerals in the dead weeds and grass are returned to the soil, ready to be used by new growth.
A big benefit of an early burn on cool-season grass is the warming impact on the soil. The sun’s energy is absorbed and passed to the soil. It’s not reflected into the atmosphere.
An underappreciated benefit: Fire helps establish clover or other legumes into grass pastures. Fire removes competition for legume seedlings. The new legume receives sunlight and moisture needed to grow.
“Fire is the gold standard for overseeding clover,” Kallenbach says. “It may not be foolproof, but I’ll just say I’ve never had a failure.” The state forage specialist recommends a 30 percent stand of clover in cool-season pastures.
The clover adds nutrients and protein to the grazing diet for livestock.
Kallenbach prefers to seed clovers in February.
This year, dry weather with windy days requires extra caution in burning.
Anyone considering using fire should attend a burn school offered by the Missouri Department of Conservation, Kallenbach says. “They do a great job of telling the requirements. That includes establishing firebreaks around the pasture to be burned. Also, back burns provide a stopping place for a fire. They teach the need to alert the local fire district of planned burns.
Above all, fires should not be lit when the weather service issues red flag warnings. Or when county commissions ban burning.
This spring, rural fire districts are stretched to their limits with wildfires. Many started as “controlled burns.”
People who have not worked a burn don’t realize how hot and fast fire can travel.
Burning a pasture requires having enough dead growth to support a hot fire, Kallenbach says. “It takes at least 1,500 pounds of dry matter per acre to sustain a useful fire. A spotty burn doesn’t do much good.”
Removing dead thatch improves spring grazing for cattle. Kallenbach compared thatch for grazing to putting last week’s leftovers on the table. “Fresh is better.”
Kallenbach is in the Division of Plant Sciences of the MU College of Agriculture, Food and Natural Resources.