Utilization refers to the amount of plant material that has been removed by animals during the grazing period. It can be based on either individual plants, key species, or an assessment of the entire management unit. However, most commonly the current year's production of accessible forage plants is considered when assessing utilization. Utilization is usually expressed as a percentage, that is calculated on a total biomass basis.
Utilization data are included in many rangeland inventory or monitoring programs as effective management tools to evaluate and modify the impact of grazing animals on vegetation resources. Livestock distribution patterns across the management unit can be classified into utilization zones, that become the basis for management decisions concerning the location of additional range improvements, such as water points, salt grounds, and fencelines. Utilization also acts as an useful index to compare the impact of different stocking strategies such as season of grazing
Comparisons of desired use and actual utilization levels during the grazing season are also valuable for evaluating stocking rates in the management unit, and adjusting livestock numbers. A common danger, however, lies in misinterpreting allowable use factors as specific management objectives, rather than as general guidelines for management decisions. Allowable use recommendations are too precise to be realistic goals for any given year, since actual percent utilization varies according to forage biomass. In addition, other factors such as the season and intensity of grazing, as well as temperature and soil moisture, have a much greater immediate effects on plant responses. Therefore, management should aim to achieve a level of actual use that, in the long term, will average to allowable use recommendations.
Some managers recommend basing utilization guidelines on residual biomass rather than forage removal. This approach better reflects the fundamental objectives of rangeland management, such as ensuring an appropriate leaf area index for initiating future growth, and protecting the surface condition and nutrient status of soils. Furthermore, residual biomass levels can be directly sampled by adopting a method to determine biomass, in contrast to other methods to determine utilization which generally attempt to account for the proportion of vegetation already removed.
Terminology Related to Utilization
The following terms are used in discussing important concepts related to utilization.
Measurement Techniques and Statistical Analysis
References and Further Reading
Cook, C.W., and J. Stubbendieck. (eds.). 1986. Range research: Basic problems and techniques.Society for Range Management, Denver, CO. pp. 120-132.
Frost, W.E., E.L. Smith, and P.R. Ogden. 1994. Utilization guidelines. Rangelands 16:256-259.
Society for Range Management. 1989. A glossary of terms used in range management. Society for Range Management. Denver, CO. 3rd ed. 15p.
Vallentine, J.F. 1990. Grazing management. Academic Press. San Diego, CA. pp. 294-320.