|Smart, Alexandr -|
|Dunn, Barry -|
|Mousel, Eric -|
|Johnson, Pat -|
|Gates, Roger -|
|Sedivec, Kevin -|
|Harmoney, Keith -|
|Volesky, Jerry -|
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 2010
Publication Date: July 22, 2010
Citation: Smart, A.J., Derner, J.D., Hendrickson, J.R., Dunn, B.H., Mousel, E.M., Johnson, P.S., Gates, R.N., Sedivec, K.K., Harmoney, K.R., Volesky, J.D. 2010. Effects of Grazing Pressure on Efficiency of Grazing on North American Great Plains Rangelands. Rangeland Ecology and Management 63:397-406. Interpretive Summary: Many individual grazing studies have been conducted evaluating livestock and vegetation responses to stocking rate treatments in the North American Great Plains. Comparisons across these studies are limited by lack of consistency in the terms light, moderate and heavy grazing at individual sites. Here, we calculated forage allowances for the different studies and stocking rate treatments to facilitate across site comparisons for 6 long-term studies in WY, SD, KS, CO, ND and OK. We determined that harvest efficiency of the livestock grazing was 42, 26, and 16% for heavy, moderate, and light stocking rates, respectively. Forage allowance was not linear with either grazing or harvest efficiency resulting in increased efficiencies at low forage allowances and decreased efficiencies at high forage allowances. Using forage allowance to “standardize” stocking rates across rangeland ecosystems should facilitate increased communications among scientists, management agencies, land managers and the public regarding this primary rangeland management practice for production and conservation goals on these lands.
Technical Abstract: Robust prediction models describing vegetation and animal responses to stocking rate in North American Great Plains rangelands are lacking as across site comparisons are limited by different qualitative designations of light, moderate and heavy stocking. Comparisons of stocking rates across sites can be facilitated by calculating a season average forage allowance using peak standing crop and stocking rate. We calculated forage allowances from six stocking rate studies in the North American Great Plains (Cheyenne, WY; Cottonwood, SD; Hays, KS; Nunn, CO; Streeter, ND: and Woodward, OK) to develop prediction models for harvest efficiency, utilization, grazing efficiency, and animal performance. Average forage allowances for heavy, moderate, and light stocking across the study sites were 28, 47, and 88 kg AUD-1, respectively. These forage allowances resulted in harvest efficiency values of 42, 26, and 16% for heavy, moderate, and light stocking rates, respectively. Utilization decreased linearly as forage allowance increased whereas grazing efficiency exhibited a curvilinear relationship (inverse function) with forage allowance indicating that non-livestock forage losses (e.g., weathering, senescence, wildlife, insects) are disproportional across stocking rates. Average daily gain of livestock was not affected by forage allowance across the range of values from these studies. Prediction models reaffirm assumptions of 50% grazing efficiency and 25% harvest efficiency associated with moderate stocking. Novel here, however, is that neither grazing or harvest efficiency scale linearly with forage allowance resulting in increased efficiencies at low forage allowances, and decreased efficiencies at high forage allowances. Use of forage allowances to “standardize” stocking rates across rangeland ecosystems in the North American Great Plains should increase communications among scientists, management agencies, land managers and the public regarding this primary rangeland management practice for production and conservation goals on these lands.