Northern Prairie Wildlife Research Center
The practice of grazing burned range changed when permanent fences were installed. Restricted movement of livestock, coupled with burning too frequently, caused changes in botanical composition of the forage and reduced livestock gains. This change in botanical composition is now recognized as a factor influencing range condition (Anderson et al 1970).
Eventually, the settlers linked the decreased production of forage and livestock to improper timing of the burns. Fire then became a management tool to maintain quality forage and increase livestock production (Anderson et al 1970; Rains et al 1975; Woolfolk et al 1973; Launchbaugh and Owensby 1978).
Although the settlers knew that increased livestock production could be obtained by proper burning of the range, it is unlikely that they completely understood the reasons. The "why" has since been researched (Arnold and Hill 1972; Ellis et al 1976; Goatcher and Church 1970) and documented as a function of palatability of the plant and preference by the animal.
The use of fire to increase livestock production is based on a recognition that forage growing after burning becomes more palatable and is preferred by livestock. A strong positive correlation between protein content and preference by cattle and sheep was illustrated by Leigh (1961).
The concepts of preference and palatability are very much interrelated and together help explain the concept of forage selection and why livestock congregate on burned sites.
There is agreement in the literature that grazing burned range versus unburned range will increase weight gains or enhance the factors that would tend to lead to increased weight gains in livestock.
Improved weight gains of livestock have occurred when fertilization is combined with burning treatments (Woolfolk et al 1973). The combination produced greater weight gains than did burned-only treatments. However, current costs of agricultural fertilizers outdistance the benefit of increased production, precluding their use.
Gains in beef production on burned versus unburned range can be attributed to changes in diet selectivity and improved forage quality, according to studies on the Edward Plateau in Texas (McGinty et al 1983).
Grass contributed a higher percentage of the diet in burned than unburned paddocks during late spring and early summer. The pattern was reversed for late summer and fall, indicating the forb component contributed a greater percentage of the diet in unburned paddocks during early and late summer. The availability of forbs was found to be less in burned paddocks as a result of the fire.
Browse structure was about even for both treatments after midspring, although diets of the steers in the control paddocks had a higher browse content in early to midspring. Live plant material intake was greater in burned paddocks in midspring because forage became more accessible to livestock after the dead plant material was burned up. The significantly increased intake of green plant material dropped off after the June sampling date.
Mineral (ash) intake in steer diets from the burned paddocks was greater in the late summer and fall. The increased ash content of the diet corresponded with more use of prickly pear cactus by the steers. Fraps and Cory (1940) found that prickly pear is high in soluble ash, possibly explaining the high ash results reported by McGinty et al (1983).
Crude protein in the steer diets on the control paddocks was greater than on the burned paddocks in the fall. Clipped plots did, however, show increased protein in the burned paddocks, but this was not reflected in the steer diets because forbs were reduced by the burn (McGinty et al 1983).
Digestibility was generally higher over the grazing season for the burned paddocks, mostly due to the increased green plant intake in the spring and prickly pear consumption in the fall (McGinty et al 1983). Forage digestibility is important because more pounds of beef can be produced from easily digestible forage than from the same quantity of less digestible forage.
Burning increased cattle production and their preference for grasses, especially weeping lovegrass (Klett et al 1971). They also found winter burns to increase forage yields 14% and utilization by cattle 53%. Burning also more than doubled crude protein, from 3.6% on untreated plots to 7.6% on unfertilized burned plots.
Fertilizer appeared to have no effect on crude protein. When it was applied to burned and unburned areas, the increase of crude protein was the same as burning alone. Allen et al (1976) also found crude protein to increase with burning but that nitrogen fertilizer had no effect.
Allen et al (1976) found certain chemical composition changes in plants after burning. Dry matter, which usually increases during the growing season, was reduced. Ether extract increased with burning. Crude fiber decreased but was increased with fertilizer application. Nitrogen free extract was decreased by nitrogen fertilizer but increased as a result of burning. Ash increased with fertilizer while fire produced little effect. Cell wall constituents increased with age, but burning lowered these constituents and improved forage quality. Neither burning nor fertilizer had any significant effect on hemicellulose, which declined with maturity. Lignin, a compound that increases as digestibility decreases, was reduced by burning but increased with fertilizer.
Heifers in the burned paddocks gained weight in June through September, while controls gained in June, July, and September. During August the heifer gains were significantly lower on controls than on burned paddocks. During the 155-day grazing period the average daily gains of the burned treatments were significantly higher than on the control treatments (McGinty et al 1983).
Hilmon and Hughes (1965) reported cattle gains of 15-27 lb/A (17-30 kg/ha) after burning forested range in Georgia and Florida. Greater palatability and production of forage were cited as the factors influencing these improved gains.
Greene (1929) reported 18 lb/A (20 kg/ha) gains on burned bluestem pasture in Mississippi with improved gains peaking 60 to 90 days post-burn. The increased live plant material was indicated to be the major cause of the improvements in the livestock gains.
Kirk and Hodges (1970) reported annual winter burning of half the range (in study pastures in Florida each year) increased the weaning crop percentage gain per calf from 9-12 lb/A (10-13 kg/ha) and gain per cow from 180-233 lb (82-106 kg) of body weight.
With burning, improved gains can be expected for steers, breeding heifers, cows, and calves. When to burn is important in achieving the desired gains and maintaining range condition for annual repeated livestock gain (Duvall and Whitaker 1964; Anderson et al 1970; Woolfolk et al 1973, 1975; Launchbaugh and Owensby 1978).
The added weight gain by the cows during the grazing season from improved forage quality or quantity could make a difference in the profit or loss statement at year's end. As McGinty et al (1983), Hilmon and Hughes (1965), and Kirk and Hodges (1970) have reported, the benefits from burning are achieved when increased forage quality is converted to meat and fiber by the animal. White and Currie (1983a) recorded increased quantity of forage which could lead to either increased livestock productivity through individual performance, or group performance through increased grazing capacity.
Work done by Smith and Young (1959) on bluestem pastures in Kansas indicated midspring burning increased protein and mineral fractions within the plant. Halls et al (1952) reported increased phosphorous and protein content in forages on coastal plains forests with midspring burning.
Anderson et al (1970) and White and Currie (1983a) found that burning in spring is the best time to improve the quality of the forage for livestock. Appropriate stocking maximizes benefits from prescribed burning.
The decision to burn should be based on anticipated forage needs and on the forage species that dominate the pastures (White and Currie 1983a,b). Improved livestock gain is no real net gain at all if range condition is compromised.
Fire can rejuvenate a pasture by increasing the numbers of seedstalks and density of desired plants. Also, cattle find these burned pastures more desirable because plants are more palatable. Ranchers like this because the nutritive value of the plants is increased and cattle gain faster.
Duvall and Whitaker (1964) set up a rotation burning system for managing longleaf pine-bluestem ranges in Louisiana. The research was conducted over 6 years where each third of the unit was burned every 3 years. The other two thirds were "naturally deferred" (avoided) by the cattle for up to 2 years.
Cattle began grazing the burned subunit within 1-4 weeks, depending on regrowth of the forage. Grazing was heavy until late summer, and little selectivity was documented. The unburned subunits were used moderately in early spring, with declining use during late spring and summer. Utilization was equal in burned and deferred subunits during late August.
When fall flowering grasses reached the late boot stage the cattle selected the seedheads in great quantity until they began to shatter out. Cattle congregated once again on the burned subunit after the seedheads became dry and unpalatable. During the winter months, cattle grazed intermittently on the burned subunit, but did not remain for extended periods (Duvall and Whitaker 1964).
Cattle gained more weight with a rotation burning system throughout the grazing season. Cattle on unburned longleaf pine-bluestem pastures in Florida rarely gained weight before calves were weaned.
Cows nursing calves on the three-pasture 3-year rotation burning system were 57 lb (27 kg)/head heavier when calves were weaned in August than in April. After weaning, these cows put on an additional 9 lb (36 kg) of body weight (Duvall and Whitaker 1964).
Ethridge et al (1985) studied the economic feasibility of burning tobosagrass (Hilaria mutica) in Texas. Burns were conducted from 1968 to 1976 on seven sites on rolling plains throughout Texas. The estimated increase in tobosagrass production resulted in a $89/A ($36/ha) increase in livestock sales over a 5-year period.
The authors concluded that the added estimated potential returns from burning must be compared to the added cost of burning.
They also stated that the main environmental variable that restrained grass production was lack of rainfall during the growing season. Wright (1969) maintains that this problem can be avoided by burning in late March when soil moisture can be more adequately assessed (Ethridge et al 1985).
Costs of burning could include fire break construction, labor, retardant cost, liability and risk factors, and other costs, depending on each situation. The economic feasibility could vary with time among ranches and among pastures within ranches (Ethridge et al 1985). Each manager must determine the cost compared to the gain on an individual basis.
In summary, the literature on prescribed burning and its effects on livestock production present enough favorable results to justify the use of fire in range management over much of the NGP.
Much of the fire-effects literature specific to the NGP has been concentrated on soils, upland plants, and wildlife, particularly birds.
Topics greatly lacking in fire effects research and literature include insects, water quality, emergent aquatic plants, trees, big game, forage crops, and livestock range. These "empty spots" in fire-effects literature are in contrast to the published materials from forest and grassland areas in other parts of the U.S. and Canada where fire research has received greater emphasis in the past.
We would like to stress a very important point: the results of burning effects from different but similar plant communities in other parts of the country are not totally adaptable to the NGP. For example, a tallgrass prairie site in the 40-inch precipitation zone of Illinois will respond to fire much differently than a tallgrass prairie site in the 16-inch precipitation zone of southern Canada.
Much remains to be learned about the effects of fire on the abiotic and biotic components of the NGP. Burning for management and research should stress seasonality, frequency, intensity, and the interaction of these variables.
Fire research needs should also include better design of experiments and pre- and post-fire evaluations including but not limited to the following quantifiable parameters: soil moisture, fuel moisture, fuel amounts (loads) and distribution, soil temperature, weather measurements, fire intensity and behavior, costs and labor effectiveness, public acceptance, and particularly, long-term evaluations of post-burn effects on the flora and fauna (both domestic and native species).
Our intent has been to provide a descriptive review of fire effects on the grassland biome of the NGP with special emphasis on the use of fire for wildlife management.
Because our interpretation of the literature may differ from yours, we encourage you to study the original research (see EC 762 for additional references) before making your own interpretations.