2017-02-16 / Opinions

Prescribed fire and grazing

Agriculture and Natural Resources Agent

The history of fire in the southeast is varied. Fires once burned as often as once a year or as infrequently as 50 years. Natural phenomena like lightning served as an ignition source before humans came in to play. Prior to European settlement Native Americans were using fires to maintain open grasslands, to promote ease of travel, increase visibility in forested areas, promote new growth of natural grains and berries, and to promote habitat for games species.

European settlers quickly learned the benefits of fire for livestock grazing. Fire controlled thick understory brush and provided abundant forage and browse. As the southeast became more settled the view of fire changed from being an invaluable tool to preventing it at all costs. Fire suppression led to the benefits of fire being ignored for decades.

Research spearheaded in the 1960s on showed an increase in overall abundance in native rangeland forage, increased palatability, increased nutrient value, and increased daily weight gains. Increase yields and nutritive value is attributed to the fact that fire removes dead plant material and stimulates new growth. Furthermore, the suppression of weeds by fire reduces competition for resources between unwanted plants and desired forage species. Yields are also increased as a result of darkening of the soil surface, which allows ground temperatures to warm quicker and stimulate earlier growth.

Benefits of fire extend beyond native grass and forb stands. Burning can also be used to improve Bermuda grass. Burning a pasture has been shown to reduce spittlebug damage in these stands. Proper timing and proper management of a prescribed burn of a pasture will result in the decrease or removal of the thatch layer that builds up over several years of growth. Buildup of the thatch layer can have several negative effects on Bermuda grass stands. It can reduce light infiltration of the grass canopy, inhibiting young stolen growth. Thatch suppresses soil temperatures in the spring, delaying green up of the field by as much as two weeks. Much like the soil in native stands, the soil in a freshly burned Bermuda field will absorb more heat energy and green up faster. A thatch layer withholds nutrients which will be available to the pasture once it is burned. Furthermore, a thatch layer can decrease water infiltration into the soil by absorbing water and causing increased runoff. Burning the thatch layer can also result in a cleaner first cutting of hay. Another major benefit is weed control because burning destroys many annual seeds, reducing the weed pressure on the pasture.

Timing of the burn is essential to exploiting its benefits. Burning too soon can promote weed regrowth during the time between burning and green up. Early burning can also cause the Bermuda grass to be more vulnerable to late freezes. Burning too late can damage Bermuda grass that has started to green up reducing overall production. A fire too hot can kill the stolens on the surface of the soil. That being said, the optimal time to burn is immediately before spring green up: this ensures that the soil surface will not be bare for too long and reduces the risk of erosion.

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