FIRE: Black Burned Land Leads to Greener Pastures

The aftermath of a fire, either prescribed or wild, can appear devastating to the untrained eye. Once the flames die down and the smoke clears, the land previously abundant with plant life appears to be nothing more than a mass of burned black soil. This depiction of destruction is far from accurate, because the land has simply been wiped clean and given a fresh start; the soil is teeming with plant life beneath the surface.

Jeff Goodwin, range and pasture consultant for The Samuel Roberts Noble Foundation, has nearly 20 years of range management experience under his belt, and previously served as a range management specialist for USDA Natural Resources Conservation Service (NRCS) in Texas. He says, “Once the smoke has lifted, the healing process has already begun.”

It’s a regenerating cycle natural for the rangelands of Texas and the Southwest. The native plants evolved under fire. In the last 150 years, the landscape of Texas has changed through urban sprawl, modern farming techniques and the division of land, interrupting the natural cycle of relief fire previously brought to the landscape.

“All of the state of Texas and every square inch of the state of Oklahoma evolved under fire frequency,” says Goodwin. “We’ve changed that by plowing up ground, introducing grasses and treating the landscape like farms. The plants that grow here are still the same plants that evolved when the bison were roaming across the prairies and those plants are resistant to fire and evolved under being burned.”

Using prescribed fire, landowners can manage invasive and native plant species by ridding the land of problematic plant life and speeding the return of nutrients to the soil. This management practice treats the rangeland and plant species using their natural adaptation to fire. To some, setting a pasture of grass on fire may seem like the act of a madman. Instead, when used correctly, prescribed fire is the tool of a smart range manager. While the landscape post-burn appears bleak, with a little bit of time, the results are surprising. The black soil holds promise that the plants will regrow and the pasture will be healthier than before.

“From an ecological standpoint, fire is not a bad thing,” says Goodwin. “It’s not a negative thing for the landscape and we need to start thinking about fire as a tool and ecological process to manage rangelands.”

Pre-planning determines post-fire management
Prior to a prescribed burn, landowners need to consider the exact goals and expectations for the pasture post-burn. Prescribed burns can be used as a tool to mitigate the negative effects of wildfires, increase wildlife habitat, rejuvenate a grass stand or control woody brush encroachment. A prescription is then written to meet a specific objective.

“We burn to meet a specific goal and then we write prescriptions to meet that purpose,” says Goodwin. “So proper planning is a key. Gather your thoughts around what you actually want to do with that piece of property.”

Long before a burn can begin, grazing rotations need to be adjusted to ensure that there is at least 1,500 to 2,000 pounds of continuous fine fuel in the pasture. Without a large fuel load, the pasture will be unable to carry a fire and the prescribed fire will be ineffective. Once a proper stand has grown, soil moisture must be tested.

To test for soil moisture before a prescribed fire, a landowner can insert a spade shovel 6 to 8 inches into the ground, pull out a soil sample and examine the soil for moisture. If the soil is cool and damp in the rhizosphere (where most of the roots are located), then the moisture level is suitable for a prescribed burn.

“I want to be able to feel dampness, moistness in that soil,” Goodwin says. “It certainly doesn’t have to be dripping, but you can tell if that soil is saturated or if it is completely dry and breaks apart and turns to dust. We don’t want to see that situation.”

Soil moisture — the regrowth key
Goodwin explains that the top contributor to immediate greenup following a prescribed burn is the presence of adequate soil moisture before the burn. After a fire, the roots of perennial grass and forages immediately begin to grow towards the surface, absorbing the moisture within the soil to repopulate the pasture. These plants will begin to add a splash of green to an otherwise black pasture within 5 to 7 days if proper soil moisture is available. Goodwin says that on closer inspection, greenup can sometimes even be seen on individual plants within a few days.

The key to sufficient soil moisture is not the amount of rain received, but instead, how the rain is managed once it lands in the pasture.

“Soil moisture is not governed by us adding moisture to the ground,” says Goodwin. “We can’t control rainfall and we cannot make it rain, but we can control how much rain we keep on the property.”

Moisture can be maintained in the soil by minimizing bare ground in a pasture. Goodwin recommends managing with a proper stocking rate and rotating to leave enough cover to provide shade and build organic matter.

“The temperature differences between bare ground soil and soil that’s covered can be 40 to 50 degrees at times,” says Goodwin.

“The hotter the soil is, the more it is losing soil moisture, so you want to keep it cool and you want to keep good soil structure.”

As organic matter grows, it adds to the soil structure and porosity, which ensures that when it does rain, the rain infiltrates into the soil and less is lost to runoff.

Goodwin recommends rest and rotation to build adequate rangeland health, but also advises that the timing of a prescribed fire can aid with soil moisture issues. In Texas, most grasses are warm-season perennials, which have a growth curve that begins in about March and ends around November. Burning closer to spring greenup will benefit the grass stand and create a quicker response.

Conversely, burning earlier will benefit forbs and other plants, but the pasture will remain black longer.

“If we can time our fires within the window of when we expect that annual precipitation with those months where we actually get most of our precipitation, we are hedging our bets to the positive side,” says Goodwin.

However, he notes that rainfall is not an issue if the pasture has proper soil moisture. In his recent work with the Noble Foundation, Goodwin burned a hot fire on a pasture in June, but the pasture had adequate soil moisture. Within 3 weeks, the pasture had 8 inches of growth on his deep rooted, warm-season perennial grasses.

“That’s the key to recovery — adequate soil moisture,” Goodwin says.

The cycle continues
Once a prescribed fire is out and the smoke has cleared, a waiting game begins. Planning for the next steps should already be in place. Depending on the goals and objectives of the burn, cattle ranchers may decide to leave the pasture out of rotation for a period as long as an entire growing season, or cattle may need to be turned out sooner.

“There are instances where, depending on your plant community, you may want to turn out immediately,” says Goodwin. “Some forages like lovegrass become unpalatable to cattle once the vegetation has matured. The young, new growth following a fire is the only time cattle will eat it.”

Post-burn management relies completely on the desired objective for the pasture, but most are ready to be returned to the grazing rotation within 60 to 90 days. Then the cycle begins all over again as the cattle play their part in managing the range until fire is needed once more.

“It’s really about when that target species gets back to a threshold where it needs to be controlled by fire,” says Goodwin.

Most of Texas has a fire return interval of anywhere from 3 to 7 years, but the decision to reburn goes back to the objective of the use of fire as a management tool. Burning intervals become longer depending on the average yearly rainfall and the speed of growth of the plant species targeted with fire. Goodwin recommends watching for regrowth or new plants to get to a level where it can be controlled with fire. Managing these species with fire can save money and time as extensive regrowth can sometimes require mechanical removal.

Through fire, the nutrient cycle is effectively turned over by breaking down organic matter and returning valuable nutrients to the soil. While a pasture going up in a plume of smoke at first appears to be an event of destruction, the black soil left behind will soon bring the reward of renewed growth.

“What we are doing is increasing and really rejuvenating that nutrient cycle by having prescribed fire,” says Goodwin.

The next time you see a pasture burned black, Goodwin says, “Remember that the land has already started healing; you just can’t see it yet.” -TC

“Greener Pastures” is from the October 2016 issue of The Cattleman magazine.