Prescribed burns aid brush management
JA Ranch managers are examining fire results to see how prescribed fires can be used for brush control in their property management.
Texas AgriLife Extension Service officials conducted a recent field day on the JA Ranch, southeast of Amarillo in Armstrong and Donley counties. Ranch operators along with AgriLife Extension and Texas AgriLife Research experts are looking at various treatments and results.
Because redberry juniper and mesquite thickly cover many pastures, it’s difficult to gather cattle, says Andrew Bivins, one of the ranch owners and leader of the Panhandle Prescribed Burning Association.
“Some of these pastures we can’t aerial spray because there is too much juniper, and it’s too rough to grub it,” Bivins says.
A prescribed burn takes time to properly plan, he says. Sometimes even after deferring grazing to build up fuel for the fire and burning black lines, the weather doesn’t cooperate for fire.
• Prescribed burning can help control dense brush on the range.
• Winter or summer burns can be conducted in the right conditions.
• Mechanical or chemical treatment can work with fire to control brush.
“To top-kill the juniper, you need moisture levels down where the canopy will burn, and enough grass where it will carry the fire from tree to tree,” says Jim Ansley, Texas AgriLife Research range management scientist, Vernon. “The problem with juniper densities like this is you could defer this for 10 years, and not get rid of the bare patches. You may have to do some mechanical treatment to open it up some and get more grass growing.”
Burn smaller portions
Ansley says an option is to burn smaller portions of a pasture on the north and east sides first, with fairly conservative fires that have pre-burned black lines. Then one could possibly push the limits in terms of humidity and air temperatures for a hotter head fire on the southern sections, assuming the burn occurs with a south or southwest wind.
The limits would include coming close to — but not below — the 20% humidity level, air temperature between 70 and 80 degrees, and wind speeds between 10 and 20 mph. “If you don’t mechanically treat it first, and want fire to do the job, you are going to have to push the limits,” Ansley says. “But this is not the most desirable situation.”
The key, says Ted McCollum, AgriLife Extension beef cattle specialist, Amarillo, is to not let the situation to get to the point where the juniper trees have to be used to move the fire.
Ken Cearley, AgriLife Extension wildlife management specialist, looks at it from a wildlife perspective. He says it would be best to leave a mosaic of plant communities in the pasture.
“If other woody cover is lacking, some cedar is better than no cedar for wildlife,” Cearley says. “If you end up not killing all of it, it’s not a bad thing. Historically, cedar existed in rougher country that protected it from naturally occurring wildfires, and provided thermal and screening cover for deer, for example.”
He suggests sometimes turning cattle in on the burned pasture a little early if quail were a major part of the operation’s plan, because that would encourage the growth of forbs for wildlife.
Frequent use of this strategy could encourage invasive brush, however, due to less grass competition. Deferment through a full growing season would be more practical if livestock is the goal.
Mesquite might not be prime cover for quail, but Cearley says if it is basically the only woody plant available, it can be managed for their use.
Cearley also says burning as early as possible in the winter generally will benefit forbs, though a good grass cover still can be expected come springtime with deferment. Burning later in the winter, just before spring green-up, will favor grasses and, therefore, livestock.
In their boggy pasture, Bivins says they spent two years to get 2,000 acres grubbed and then deferred it for a year before burning it in 2003. The grubbing and burn combination did a good job of clearing up the brush growth.
“We like to wait a year or two after grubbing before we burn, but you don’t want to wait too long,” he says.
Bivins also says that everything didn’t catch fire the first day, and he and his mother went out the next two days with drip torches to light fires for better coverage. He estimates $120 an acre to grub, so they have started to bulldoze two lines 100 yards apart and grub in between. Afterward, they let the area sit for a year before burning it as a black line. This procedure is followed by fire across the rest of the pasture.
“To keep the mesquite suppressed, you really should burn it every six to seven years,” Ansley says. “Redberry juniper has a slower regrowth and you can get by with 10-year intervals.”
He says in studies of mesquite seedlings, they discovered the growth node can slip back under the soil surface in the early stages of growth to protect it from fire, so earlier burning may not do a good job.
“While fire may be very hot at the soil surface, at a half-inch down in clay soils, you won’t have any temperature difference,” Ansley says.
Ansley says summer is when many of the wildfires started years ago, and while it may not be the practice now, they have benefits. Summer fires have a higher duration of extreme heat, which can top-kill brush species easier. “We don’t recommend it in cedar country, but with mesquite and prickly pear, it’s doable and more effective,” he says.
Warm-season grasses may be delayed by a summer fire, but the long-term data shows that after a few years, the reverse happens, Ansley says. “We have more warm-season mid-grasses replacing warm-season short grasses like buffalograss,” he notes. “So in the long run, if you can arrange a management scheme where you can tolerate the slower recovery, a summer fire will be better.”
Studies show if mesquite is only top-killed, the original canopy cover as a percentage of ground area returns within just a few years because of rapid multi-stemmed regrowth. Mesquite regrowth has more leaf area than before, and can become a greater problem than the original plant.
Treatments that maintain top-kill and keep mesquite canopies as a savanna can be another option. Low-intensity fires or spraying Reclaim by itself can be used for this option, Ansley says. These treatments will reduce the canopy foliage to about one-third the size and keep the mesquite from resprouting.
Resprouting replaces single- or double-stemmed mesquite trees with multiple-stemmed trees.
Ledbetter is with Texas A&M Agriculture Communications, Amarillo.
This article published in the February, 2010 edition of THE FARMER-STOCKMAN.