When burning costs are mentioned, fireguard establishment and labor for a burn are usually the topics of discussion. However, some argue that burning native grass pastures may have more significant costs such as decreasing plant diversity, destroying wildlife habitat, decreasing forage production or adversely affecting soil chemistry.
Annual burning for long periods of time may have a negative effect on native plant diversity. Annual spring burning on the Coffey Ranch strongly favors broomsedge bluestem monocultures. However, burning can also be used to stimulate plant diversity.
Burning at a different time of the year and at different intervals can encourage a variety of grass and forb species to grow in monocultures. Also, a successful burn in closed canopy timber can increase plant diversity by allowing sunlight to reach the soil and stimulate the growth of shrubs, grasses and forbs. Remember, burning is a tool. Like other tools, it can be used improperly.
With the possible exception of livestock, burning is probably the most useful and economical tool available to manipulate wildlife habitat. Under the right conditions and with proper timing and frequency, burning can be very beneficial to many wildlife species. Burning grass monocultures during the winter months can stimulate forb production for quail.
Burning closed canopy timber as mentioned above can create plant diversity which is valuable as food and cover to deer, quail and turkey. As with livestock, if improperly applied, burning can have negative effects on wildlife as well. An example would be burning pastures to reduce brush canopy coverage below 5%, which would be detrimental to quail.
Obviously, burning will reduce available forage at the time of the burn and a recovery period is usually required after the burn. Plants also need a growth period before the burn to allow for fuel accumulation. All of these statements imply a loss of forage, but not necessarily for a full year.
Pastures targeted for burning can be utilized for a portion of the year scheduled for burning. For instance, burning in the spring followed by an intensive early stocking program with rest from July to frost may allow near full utilization of a pasture. Burning can also be used to influence livestock distribution within a pasture.
This year we will burn about a third of a pasture on the Coffey Ranch that we are having trouble getting the livestock to utilize. Although the cattle have access to it, we have adequate fuel to burn because of the lack of utilization. The pasture will remain in the normal rotation after the burn to encourage the cattle to graze the burned area. Native grass forages can also be stockpiled after a burn and used as standing hay after frost.
Burning releases the minerals tied up in plant material. When ashes are leached into the soil surface, soluble salts, pH, phosphorus and nitrogen are increased and the carbon to nitrogen ratio is decreased. Some nitrogen is volatilized due to combustion. However, the remaining nitrogen is readily available as ammonia nitrogen or through microbial nitrate nitrogen. This probably contributes to the robust plant growth following a burn (Vallentine, 1989).
Soil moisture should also be considered when burning. Decreased soil moisture following a burn due to higher soil temperatures and increased runoff is usually temporary, especially in areas with annual precipitation of 30 to 35 inches or more. However, even in these areas, burning should be carefully evaluated in times of drought.
With adequate soil moisture, plants recover rapidly and endure little stress. Without soil moisture, plants can be stressed and range condition can deteriorate. The key to obtaining desired results from burning is proper planning. Planning a burn should begin at least one year in advance. Let us know if you need to know where to begin.
Vallentine, J.R. 1989. Range Development and Improvements (3rd ed.). Academic Press, Inc. San Diego, California.