|Hart, Richard - RETIRED USDA-ARS|
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 6, 2004
Publication Date: May 15, 2005
Citation: Andales, A.A., Derner, J.D., Bartling, P.N., Ahuja, L.R., Dunn, G.H., Hart, R.H., Hanson, J.D. 2005. Evaluation of GPFARM for simulation of forage production and cow-calf weights. Rangeland Ecology and Management.58:247-255. Interpretive Summary: Land managers are in need of methods to evaluate impacts of, and reduce decision making risk in, implementing alternative management decisions. A newly developed decision support system for the central Great Plains, the Great Plains Framework for Agricultural Resource Management (GPFARM) model, was used to determine its ability to simulate forage production in shortgrass prairie and cow-calf production in northern mixed-grass prairie. The forage module displayed good agreement in tracking plant functional group growth and senescence trends, although warm-season grass biomass peaked earlier compared to observed data. The cattle module performed well and tracked cow and calf pre- and post-weaning weights. This model has functional utility for rangeland and livestock production system managers as a decision support system.
Technical Abstract: A modeling approach that assesses impacts of alternative management decisions prior to field implementation would reduce decision-making risk for rangeland and livestock production system managers. The goal of this study was to evaluate the functionality of the Great Plains Framework for Agricultural Resource Management (GPFARM) model in simulating forage and cow-calf production in the Central Great Plains. The forage production module was tested in shortgrass prairie using April-October monthly biomass values from 2000-2002 for warm-season grasses, cool-season grasses, shrubs and forbs. The forage module displayed good agreement in tracking functional group growth and senescence trends. Further investigation is needed to determine why simulated warm-season grass biomass peaked earlier compared to observed data. The cow-calf production module was tested in northern mixed-grass prairie using June-November monthly average cow and calf weights from 1996-2001 for March-calving, moderately stocked Hereford pairs. Overall, GPFARM performed well and tracked cow and calf pre- and post-weaning weights. Further model work should focus on the calf gain algorithm post-weaning as calf weights were under-predicted. The GPFARM model has functional utility for rangeland and livestock production system managers as a decision support system. Continued developments will focus on expanding this utility by incorporating environmental risk, additional management operations and within-year flexibility.