Texas Cooperative Extension range expert Wayne Hanselka says pastures need protection from wildfire, and the most common is fire guards around and through pastures.
The more permanent types of fire guards are done mechanically, often with a disc, blade or plow. Grasses are removed or turned under the soil so that bare soil is exposed. Any grasses occurring on the line could form a “bridge” that allows fire to creep across the line. These fire guards need to be at least three times as wide as the adjacent vegetation is tall (3 feet-high grasses = 9 to10 feet or more of fire guard). A flame front should approach the guard, lay down over it, and not touch the far side of the guard.
Temporary guards can be constructed by mowing excess fuel, he says. The remaining stubble will still burn but not with the intensity or rate of spread supported by higher fuel loads. A strip is mowed around a pasture with a disced or bladed line next to it. Another strip is mowed to eliminate tall grasses from the plowed strip.
“Another combination is to use two lines — mechanical, wet lines using water, and/or chemical lines (a super phosphate slurry) — at an appropriate distance apart,” he says.
“The space in between is then burned out. This effectively removes any fuel for a distance away from the perimeter of the pasture. It is effective for season-long protection. Of course, the burning of these ‘blacklines’ should be done when conditions allow them to be safely burned. Widths vary with the kind and amount of fuel present. Blacklines should be at least 100 feet wide in grasslands with oak or mesquite brush. In volatile brush such as cedars, the black line probably should be at least 500 feet wide.”