Using a Model and Forecasted Weather to Predict Forage and Livestock Production for Making Stocking Decisions in the Coming Growing Season

Forecasting peak standing crop (PSC) for the coming grazing season can help ranchers make appropriate stocking decisions to reduce enterprise risks. Previously developed PSC predictors were based on short-term experimental data (<15 yr) and limited stocking rates (SR) without including the effect of SR on PSC explicitly. Here we used long-term (30 yr) measured data of PSC and steer weight gain (SWG), extended with the help of a model for SR effect, to develop multiple-variable regression functions for predicting PSC and SWG across a wide range of SR (0.2–1.32 steers ha−1 for summer grazing season, June to mid-October) on a loam soil in a northern mixed-grass prairie. April to June rainfall was the primary weather variable influencing PSC (R2 = 0.45); inclusion of SR and soil water content on 1 April improved the accuracy in predicting PSC (R2 = 0.64). Combining the response of PSC to SR and the response of SWG to both PSC and SR enables ranchers to explore tradeoffs between economic net return and environmental impact (land conservation) as influenced by SR and weather variations. The result was further extended from the loam soil at the experimental site to the other two soil types (loam sandy and clay loam soils) by using a simple soil influence factor. A simple spreadsheet-based decision support tool can be developed to facilitate stocking decisions by ranchers in a northern mixedgrass prairie to adaptively manage rangelands in an effort to increase economic net return and reduce land degradation associated with high weather variability and SR levels. Abbreviations: DC, Drought Calculator; HPGRS, High Plains Grasslands Research Station; HPPSC, peak standing crop; GPFARM, Great Plains Framework for Agricultural Resource Management; PSC, peak standing crop; SR, stocking rate; SWG, steer weight gain; TDN, total intake digestible nutrient. Quan X. Fang Agronomy College, Qingdao Agricultural University, Changcheng Road 700, Chengyang District, Qingdao, Shandong, China, 266108. *Corresponding author (fangqx@igsnrr.ac.cn) L.R. Ahuja, USDA-ARS-NPA-ASRU 2150 Centre Ave., Bldg. D, Ste. 200 Fort Collins, CO, 80526 (laj.ahuja@ars. usda.gov) A.A. Andales, Department of Soil and Crop Sciences, Colorado State University, 1170 Campus Delivery, Fort Collins, CO 80523-1170 (Allan.Andales@colostate.edu). J.D. Derner, USDA-ARS, High Plains Grasslands Research Station, 8408 Hildreth Road, Cheyenne, WY 82009-8899 (Justin.Derner@ars.usda.gov) doi:10.2134/advagricsystmodel5.c7 Published December 5, 2014

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