Barry H. Dunn

Using Weather Data to Explain Herbage Yield on Three Great Plains Plant Communities

Abstract Understanding the drivers that account for plant production allows for a better understanding of plant communities and the transitions within ecological sites and can assist managers in making informed decisions about stocking rates and timing of grazing. We compared climatic drivers of herbage production for 3 plant communities of the Clayey ecological site in southwestern South Dakota: the midgrass community dominated by western wheatgrass (Pascopyrum smithii [Rybd.] A. Love); the mixed-grass community codominated by western wheatgrass, blue grama (Bouteloua gracilis [H.B.K.] Lag. Ex Griffiths), and buffalograss (Buchloe dactyloides [Nutt.] Engelm.); and the shortgrass community dominated by blue grama and buffalograss. We used herbage yield and weather data for the period 1945–1960 collected at the South Dakota State University Range and Livestock Research Station near Cottonwood, South Dakota, to develop stepwise regression models for each plant community. Midgrass herbage production was best predicted by current-year spring (April–June) precipitation, number of calendar days until the last spring day with minimum temperature ≤ −1°C, and previous-year spring precipitation (R2 = 0.81). Mixed-grass herbage production was best predicted by current-year spring precipitation and days until the last spring freeze (R2 = 0.69). Shortgrass herbage production was best predicted by current-year spring precipitation (R2 = 0.52). Midgrass plant communities were, overall, 650 kg·ha−1 (SE = 92 kg·ha−1) more productive (P < 0.01) than mixed- or shortgrass plant communities given the same climatic inputs. Our study enables managers to make timely informed decisions regarding stocking rates and timing of grazing on this ecological site in western South Dakota.

Effects of Grazing Pressure on Efficiency of Grazing on North American Great Plains Rangelands

Abstract Comparisons of stocking rates across sites can be facilitated by calculating grazing pressure. We used peak standing crop and stocking rates from six studies in the North American Great Plains (Cheyenne, Wyoming; Cottonwood, South Dakota; Hays, Kansas; Nunn, Colorado; Streeter, North Dakota; and Woodward, Oklahoma) to calculate a grazing pressure index and develop relationships for harvest efficiency, utilization, grazing efficiency, and animal performance and production. Average grazing pressures for heavy, moderate, and light stocking across the study sites were 40, 24, and 14 animal unit days · Mg−1, respectively. These grazing pressures resulted in average harvest efficiency values of 38%, 24%, and 14% and grazing efficiencies of 61%, 49%, and 39% for heavy, moderate, and light stocking rates, respectively. Utilization increased quadratically as grazing pressure index increased, whereas grazing and harvest efficiencies exhibited a linear increase with grazing pressure. The latter indicates that nonlivestock forage losses (e.g., weathering, senescence, wildlife, insects) were disproportional across stocking rates. Average daily gain of livestock decreased linearly as grazing pressure index increased across study sites. Prediction equations reaffirm assumptions of 50% grazing efficiency and 25% harvest efficiency associated with moderate stocking. Novel here, however, is that harvest and grazing efficiencies increased at high grazing pressures and decreased at low grazing pressures. Use of grazing pressure index to “standardize” stocking rates across rangeland ecosystems in the North American Great Plains should improve communication among scientists, resource managers, and the public, and thus better achieve both production and conservation goals on these lands.

Historical Weather Patterns: A Guide for Drought Planning

H ow do we know when drought will occur? In 2002, the Great Plains suffered through a widespread drought that seemed to catch many ranchers off guard. In South Dakota, there was a flurry of extension activity generated to deal with drought issues. Why were so many ranchers caught off guard? One answer may reside in the patterns of past weather data. Being able to anticipate low rainfall and having the flexibility to handle it has been the common advice by extension personnel and ranchers that have successfully weathered the years. To do this, one has to develop the ability to evaluate historical data in regard to making decisions that have long-term implications for successfully navigating through ranching challenges. Our objective is to present historical precipitation data from western South Dakota and derive certain expectations of drought occurrence to show how this can be used in drought planning.

Barriers to Successful Drought Management: Why Do Some Ranchers Fail to Take Action?

Barriers to successful drought management: why do some ranchers fail to take action? DO:10.2458/azu_rangelands_v27i2_dunn

A systems approach to forecast agricultural land transformation and soil environmental risk from economic, policy, and cultural scenarios in the north central United States (2012–2062)

ABSTRACT Grassland conversion to row-crop production in the north central United States has been a growing threat to socio-economic and environmental sustainability for producers, conservationists, and policy-makers alike. We used a system dynamics model of the region to forecast agriculturally driven land transformation through mid-twenty-first century. The base-case scenario projection showed that farmland area continued to increase, from under 200,000 km2 to over 230,000 km2. Unmitigated, the soil environmental risk (SER) of such changes reached conservative estimates of Dust Bowl-era externalities. Systems analyses show that reducing livestock production costs, doubling conservation compliance requirements, and livestock–cropping integration had the largest impact on grassland conservation and mitigating SER. The largest SER effects came from eliminating conservation incentives or raising cultivation incentives, despite improvements in reduced tillage and enhanced agronomy. Several system archetypes were identified within the policy scenarios: ‘fixes that backfire’ and ‘success-to-the-successful’. For scenarios creating favourable impacts, time delays caused some behaviours to worsen before positive gains were realized. If implemented, patience and persistence to ensure that these scenarios reach their full potential will be necessary. Our scenarios provide quantitative forecasts around measures for sustainable intensification. These projections can aid regional stakeholders in enhancing discussions currently taking place about sustainable agriculture in the region.

CASE STUDY: Profitable marketing and business practices on a South Texas ranch

ABSTRACT In this case study, historic production and financial records of the cow-calf, stocker, and feedlot enterprises of a South Texas ranch for the years 2001 through 2008 were analyzed. Most of the raised calves were sold at weaning. Depending on precipitation and forage, native stocker cattle were bought during the fall and spring and marketed the following spring and summer. The ranch also managed a feedlot operation, buying feeder cattle and selling finished cattle to a local packer. Annual and cumulative profit or loss on a per animal basis was calculated for each enterprise. For comparison, a retained ownership scenario was developed using the accumulated costs and returns from representative cattle of ranch origin retained through the stocker and finishing phase. When compared with retained ownership, the historic production and marketing plan resulted in greater (P

Strategic Management and Ranching: Successfully Planning for the 21st Century

Strategic Management and Ranching: Successfully Planning for the 21st Century DOI:10.2458/azu_rangelands_v30i2_dunn2

King Ranch Institute for Ranch Management Symposium on Excellence in Ranch Management.

King Ranch Institute for Ranch Management Symposium on Excellence in Ranch Management DOI:10.2458/azu_rangelands_v29i2_dunn