Lighting a tallgrass prairie on fire might seem contrary to common sense, because it’s almost like starting a wildfire. But if carefully planned, controlled fires are quite beneficial.
While there’s always an element of risk when setting an intentional fire, prescribed burning helps reduce the danger of wildfire by removing excess fuel in the form of dead grass and debris.
Why Do a Controlled Burn?
About 82,000 acres of the world’s tallgrass prairie extend across Kansas and into north-central Oklahoma. The largest portion falls in the Flint Hills region of Kansas. Natural wildfires, and now prescribed burns, are essential to this ecosystem’s preservation. Grazing cattle prefer the fresh green grass that grows following a burn, and removing the previous season’s thick, dead thatch promotes nutritious new growth for livestock forage.
The deep roots of prairie grasses remain undamaged by the intense heat, while the fire removes parasites that may have overwintered in the dead grass. Fire can also destroy the seeds of noxious weeds and other unwanted plants, such as the invasive eastern red cedar on the Great Plains. An added benefit is the lowered risk of eye infection in the herd caused by scratching from tall blades of grass.
Controlled Burning Techniques
Flint Hills rancher Todd Krispense shared with me the ins and outs of pasture management and controlled burning techniques. Not every patch of prairie needs to be burned every year, he pointed out. Research studies on the Great Plains have shown the optimal cycle to be every three years. Burning sections of grass on a rotational schedule preserves habitat for native insects and the threatened greater prairie chicken, among other animals.
If you have a grassy pasture and want to learn how to do a controlled burn, you should first evaluate the patch. Sufficient soil moisture is one factor to consider. Burning too early in spring can increase surface evaporation. Generally, the soil’s surface should be damp when you conduct a prescribed burn. Also, the soil below the surface should be moist to the depth of the grass roots, meaning you can squeeze excess water from a handful of soil. This is especially true for sandy soils. Also, consider the air’s relative humidity, and aim for a reading between 30% and 55%.
The timing of your pasture burn can affect the growth of different grasses; however, a long-term study conducted in the Flint Hills didn’t find any significant effect on grass production when burns were done in either fall, winter, or spring.
Perhaps most important for safe controlled burning techniques is to evaluate the wind on the day you plan to burn. The fire direction should always be against the wind and conducted in maximum wind speeds of 15 mph. Line up adequate help and plenty of water in spray tanks, and get the appropriate permit from authorities. Contact neighbors of the land you’re burning so they’re aware of your plans.
Before you strike the match, establish a fireguard around the perimeter of the burn area. Fireguards are obstructions that can be natural (such as a river) or human-made (pre-burned grass).
To create a fireguard, you can light a backfire along the downwind side of the pasture — generally where you want the main fire to stop burning. This smaller patch of pre-burned ground will prevent the main fire from roaring into an adjacent pasture, as fires don’t respect fences or boundary lines, and you don’t want to destroy a neighbor’s property.
Decide on the best location for a backfire strip and then establish a water line, also known as a “wet line,” as a firebreak for stopping the backfire. To make a water line, spray water 1 to 3 feet wide, soaking the grass along the backfire strip on the side you don’t want the bigger fire to burn. Many ranchers do this with a spray tank on the back of a flatbed pickup truck. They spray the grass and then drive down the wet strip with a truck to compact the tall grass before lighting the water line on fire. The water line should be allowed to burn slowly and thoroughly to avoid partially burnt stems that can give the fire a means to jump across the line.
Exercise caution, because fire can jump a water line. Station your helpers with spray tanks along the line, and make sure truck-mounted sprayers are available to stop the fire in case the wind changes direction. To lessen the risk, you can also mow a strip along one side of the water line to remove excess fuel — but remain vigilant.
Controlled Burn Tools
After the backfire is under control and has burned in the right direction a bit, you can light the main fire. A homemade device called a “fire stick” is the controlled burn tool of choice in the Kansas Flint Hills. This is a length of steel pipe filled with gasoline and capped at both ends. The pipe’s working end is lit and dribbles fire as it’s pulled behind an ATV. When the ATV operator is ready to pause, they simply lift the stick in the air to stop the fuel from continuing to leak. No oxygen enters the closed system, so explosion isn’t a risk.
The main fire should be lit against the wind so the person lighting it won’t be caught in a corner. Continue to double back throughout the burn event to make sure no sparks or burning manure piles have blown into a patch of grass and flared up.
A successful pasture burn is often an amazing sight to behold as huge billows of smoke form clouds in the sky. And when you appreciate the risks and understand the benefits, this sight can spark wonder instead of fear.
Along with learning how to do a controlled burn, other important factors you’ll need to consider for a successful pasture-management plan include mastering noxious and invasive weeds and trees, using appropriate stocking and grazing rates, taking proper care of fencing, and keeping a watchful eye for erosion.
Native grasslands are made up of a mixture of cool- and warm-season perennial grasses (such as big and little bluestem and gamagrass), legumes (alfalfa, clovers, and more), and forbs (flowering, broad-leafed plants). Burning doesn’t hurt perennial grasses, and it helps control invasive weeds and small trees.
Noxious weeds in native pastures vary by location. In many areas, musk thistle (Carduus nutans) and sericea (Lespedeza cuneata) are considered a problem and should be removed if found in a pasture. Other unwanted plants include staghorn sumac (Rhus typhina), buckbrush (Ceanothus cuneatus), and bull thistle (Cirsium vulgare). Untended trees, such as Osage orange (Maclura pomifera), honey locust (Gleditsia triacanthos), and eastern red cedar (Juniperus virginiana), can present a problem if left untended, but they’re usually effectively managed through proper controlled burning techniques.
Fences Make Good Sense
A solid, dependable fence is essential when grazing stock on your pasture.
Conduct a thorough check of all fences in each pasture at the beginning of the grazing season, and then continue to check on the fence and the electric fence charger, because repairs and battery replacement could be needed at any time.
A five-strand barbed-wire fence is most common in the Flint Hills, sometimes in combination with an electrified fence. Cattle tend to wear a path inside a fence, working the ground away from the posts and causing them to fall over. For this reason, some ranchers like to set up an electrified fence several feet inside the barbed wire to prevent their animals from walking next to it.
Erosion can sometimes occur around ponds and spillways. You can install a fence to keep cattle from grazing these areas bare.
Ashleigh Krispense enjoys baking, gardening, and raising chickens with her husband on their central Kansas farm. Follow her at Prairie Gal Cookin’.
Originally published as “Big Burns” in the April/May 2023 issue of Mother Earth News and regularly vetted for accuracy.