Prescribed burning

Prescribed or controlled burning is a technique sometimes used in forest management, farming, or prairie restoration. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest. Some seeds, such as sequoia, remain dormant until fire breaks down the seed coating.

Another consideration is the issue of fire prevention. In Florida, during the drought in 1998, catastrophic wildfires burned numerous homes. But forestry managers note that the underlying problem was prior cessation of controlled burning, due to complaints by homeowners. Each year additional leaf litter and dropped branches increased the likelihood of a hot and uncontrollable fire.

George D. Kessler, professor of forestry, and extension forester at Clemson University notes that controlled burning reduces fuels, may improve wildlife habitat, controls competing vegetation, improves short term forage for grazing, improves accessibility, helps control tree disease, and perpetuates fire dependent species. In old growth longleaf pine forest, it helps maintain habitat for endangered Red-cockaded Woodpeckers in their sandhill and flatwoods habitats. However many scientists disagree with such a simplistic approach, and indicate that each forest must be assessed on its own merit.

In industrialized counties, controlled burning is usually overseen by fire control authorities for regulations and permits. The party responsible must delineate the intended time and place. Obtaining a permit may not limit liability if the fire burns out of control.

Controlled burns are sometimes ignited using a tool known as the driptorch, which allows a steady stream of flaming fuel to be directed to the ground as needed. Variations on the driptorch can be used such as the helitorch, which is mounted on a helicopter, or other improvised devices such as mounting a driptorch-like device on the side of a vehicle. A pyrotechnic device known as the fusee can also be used in ignition.

For the burning of slash, waste materials left over from logging, there are several types of controlled burns. Broadcast burning is the burning of scattered slash over a wide area. Pile burning is gathering up the slash into piles before burning. These burning piles may be referred to as bonfires. High temperatures can harm the soil, damaging it physically, chemically or sterilizing it. Broadcast burns tend to have lower temperatures and will not harm the soil as much as pile burning, though steps can be taken to treat the soil after a burn. In lop and scatter burning, slash is left to compact over time, or is compacted with machinery. This produces a lower intensity fire, as long as the slash is not packed too tightly. However, soil may be damaged if machinery is used to compress the slash.

In addition to forest management, controlled burning is also used as an agricultural technique called slash and burn, one component sometimes used by shifting cultivators as a part of field preparation for planting. The controlled burn is used to clear the land of any existing crop residue as well as kill weeds and weed seeds. A controlled burn is less expensive than most other methods such as herbicides or tillage but because it does produce smoke and other fire related pollutants, its use is not popular in agricultural areas bounded by residential housing. In the United States, controlled burning is a legislative and regulatory issue at both the Federal and state levels of government.