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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCED SYSTEM MODELS AND DECISION SUPPORT TOOLS TO OPTIMIZE WATER LIMITED AGRICULTURE

Location: Agricultural Systems Research Unit

Title: Simulation of sandsage-bluestem forage growth under varying stocking rates

Authors
item Adiku, Samuel G. -
item Dunn, Gale
item Ahuja, Lajpat
item Gunter, Stacey
item Bradford, James
item Garcia, Luis -
item Andales, Allan -

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2010
Publication Date: September 1, 2010
Citation: Adiku, S.K., Dunn, G.H., Ahuja, L.R., Gunter, S.A., Bradford, J.A., Garcia, L., Andales, A.A. 2010. Simulation of sandsage-bluestem forage growth under varying stocking rates. Rangeland Ecology and Management. 63(5):546-552.

Interpretive Summary: The effect of stocking rate on forage growth has attracted much research attention in forage science. Findings show that forage growth may be affected by stocking rate, and there is a consensus that high stocking rates lead to soil compaction, which could also in turn affect forage growth. In this study we used a modeling approach, by using GPFARM-Range to investigate the effect of stocking rates on the growth of sand-bluestem forage at Fort Supply, Oklahoma. We have shown that by modeling changes in soil bulk density under high stocking rates observed losses in forage production can be predicted. The ability to simulate the effect of soil compaction on forage growth is a further improvement in our ability to predict long-term effects of stocking rates on forage growth and hence rangeland management. Modeling with GPFARM-Range, provides that foreknowledge that can determine the best management for reducing deterioration of rangeland conditions.

Technical Abstract: The effect of stocking rate on forage growth has attracted a great deal of research attention in forage science. Findings show that forage growth may be affected by stocking rate and there is the consensus that high stocking rates lead to soil compaction, which could also in turn affect forage growth due to the changing soil hydrology and increased soil impedance to forage root penetration. In this study, we used a modeling approach to investigate the effect of stocking rates on the growth of sand-bluestem forage at Fort Supply, OK. The GPFARM-Range model, which was originally developed and validated for Cheyenne, WY., was re-calibrated and enhanced to simulate soil compaction effects on forage growth at Fort Supply. Simulations without the consideration of soil compaction effects overestimated the forage growth under high stocking rate conditions (mean bias, MBE = -591 kg ha-1) and the agreement between the simulated and observed forage growth was poor (Willmott’s d = 0.47). The implementation in the model of soil compaction effects associated with high stocking rates reduced the bias (MBE = -222 kg ha-1) and also improved the overall agreement between the observed and the simulated forage growth (d = 0.68). It was concluded that forage growth under increasing soil compaction could be predicted provided such sensitivities are included in forage growth models.

Last Modified: 9/22/2014