192 - Outcomes of Simulated Combinations of Rangeland Management Scenarios on Soil and Nutrient Processes

Abstract: The relationships among rangeland management practices and ecosystem on soil and nutrient processes are complex. Simulation models can provide valuable insight into this complexity to guide future research and management decisions for sustainable grazing systems. The objective of this analysis was to evaluate the combinations of grazing management (continuous vs. rotational), stocking rate (low, moderate, or high), and burning (none vs. annual spring burn) on soil erosion, nutrient losses, and carbon sequestration. Soil, weather, and forage species data were collected for 3 locations in the Central Great Plains (Konza Prairie Biological Station, Kansas; Agricultural Research Center-Hays, Kansas; Central Plains Experimental Range, Wyoming). These data were used to simulate combinations of rangeland management scenarios using the Agricultural Policy/Environmental eXtender (APEX) model. A stocker cattle operation was simulated at Hays, Kansas and Wyoming locations, and a cow-calf operation at Konza, Kansas location. Burning increased soil loss from water erosion regardless of stocking rate or grazing management. Rotational grazing increased soil loss at the Kansas locations, but decreased soil loss at Wyoming compared with continuous grazing. Stocking rate had little effect on nitrogen losses, but rotational grazing decreased nitrogen loss compared with continuous grazing. Greater stocking rates slightly decreased phosphorus losses with continuous grazing, but not rotational grazing. Burning decreased phosphorus losses with continuous grazing at Konza, but not the other locations. Greater stocking rates decreased the deposition of soil organic carbon especially with continuous grazing, and burning resulted in losses of soil organic carbon at Konza and Wyoming. In conclusion, rangeland management practices differentially affect nutrient processes among ecosystems such that a one-size-fits-all management scheme will not maximize retention of all nutrients in all ecosystems.