Fire Lines for Controlled Burns

Fire lines are a break in fuel around the perimeter of a burn unit. They keep the fire contained within a desired area. Adequate fire lines are imperative and are often overlooked, or an after thought.

The picture shows a mowed and broomed fire line in the tallgrass prairie.

Types of Fire Lines

Many types of fire lines can be utilized for a burn including natural fire breaks, roads, mowed fire lines, plowed fire lines and disced fire lines. All of these can be beneficial, depending on objectives, fuel types, fuel moisture, weather, etc.

Natural Fire Breaks

Natural fire breaks can include ponds, creeks, rivers, drainages, cattle trails, feed grounds, or anything that is a natural break in fuel. We utilized all of these when we they fit our objectives. For example, we wouldn’t utilize a cattle trail in the tallgrass prairie on a 30% humidity day in March. We may however use a cattle trail as a line to light a backfire off of first thing in the morning when the humidity is high.

Roads

Roads are an excellent option to use as fire lines when planning a burn. Many types of roads can be used including paved roads, gravel roads and even pasture roads in the right conditions. We utilize roads if at all possible, as they are usually a very reliable fire break.

Mowed Fire Lines

Mowed fire lines can be an excellent fire line choice, when done properly. However, they can also create problems. When a fire line is mowed, all of the cut plant material, or “duff”, is left along the line, which can create big problems when least expected. A fire may appear to be out along the line, when in fact it is smoldering under the “duff” while the crew walks off in assumption the line looks good. We have seen fires escape like this time and time again.

Mowed and grazed fire lines can be an excellent choice. If the mowed lines are cut short months ahead of time, cattle will often graze these areas which will keep these areas green and short.

Mowed and Broomed Fire Lines

These fire lines are mowed, very short, and followed up with a broom attachment which removes all of the cut plant material from the line. We no longer utilize mowed lines unless they have also been broomed. We provide fire line installation for clients with our mower and broom attachment. Contact us for inquiries on installing fire lines.

Plowed Fire Lines

Plowed fire lines are a break around the burn unit with a plow. The plow cuts a line in the soil, creating a bare ground fire break. Plowed fire lines can be a great option if this is a piece of equipment already owned. However, we have seen fires cross plowed lines that leave clumps of grass on the line in lower humidity conditions. They also create somewhat of a “mess” around the unit. Unless the area is smoothed out following a burn, large cuts and big clumps are left behind. Plowed fire lines can be difficult to use in rocky soil types.

Disced Fire Lines

Disced fire lines are very similar to plowed lines. However, instead of plowing a narrow line, the lined is disced up with multiple blades which creates a wider break in fuel. Disced lines can be beneficial in areas with few rocks. If the objective of the burn requires lower humidity, the line may need to be disced more than once to create a complete break in fuel with no plant material where the fire can creep across the line. Many times disced lines are utilized in areas to attract wildlife, such as dove and quail. The soil disturbance will create a flush of annual forbs which attracts many species of wildlife.

What Type of Fire Line Should I Use?

It all depends on the burn unit, your resources, and your objectives. Yes, a mowed and unbroomed line would work for a fire in 80% humidity, but it is likely those weather conditions won’t actually achieve your objectives.

Like with any project, start out with your objectives and work from there.

• Objectives (wildlife, grazing, brush control, invasive species management, etc.)

• Resources (roads, natural fire breaks, available equipment, etc. )

• Make a plan (create your burn plan and get your fire lines prepared ahead of time)

We provide a suite of controlled burn services including: start-to-finish burns, writing burn plans, writing smoke management plans, and installing fire lines. Contact us to inquire about these services.