South Dakota Drought Tool Supports Ranch Management

By Scout Nelson

For more than 25 years, ranchers in South Dakota have used the South Dakota Drought Tool to estimate forage productivity on grazing lands. The tool helps producers decide whether they should increase or reduce herd sizes for the following season. Government agencies and land managers also use the tool to balance forage use between livestock and wildlife.

Stan Boltz, a regional soil health specialist with the Natural Resources Conservation Service, developed the South Dakota Drought Tool after recognizing the need for a reliable system to help ranchers manage grazing conditions during dry periods.

“Stan was well-respected in understanding the producer’s needs,” explains Jackie Ott, a Research ecologist with the Forest Service Rocky Mountain Research Station based in Rapid City.

The drought tool uses environmental information such as rainfall from previous years to estimate forage growth. Researchers explain that rainfall from the previous year has a stronger effect on current forage production than precipitation received two years earlier. The system includes several models that reflect changing weather patterns across South Dakota.

Although producers successfully use the tool for many years, researchers later work to document the science and mathematical equations behind the model. Jackie Ott, statistician Shannon Kay, and State Rangeland Management Specialist Emily Helms Rohrer worked with Boltz to explain and validate the calculations used by the drought tool.

During the validation process, researchers improved the model by adding more accurate estimates of long-term forage productivity based on soil types. “The model actually predicts what producers often observe,” Ott explains. The tool also allows ranchers to enter local rainfall information to better match conditions on their own land.

Boltz passed away before the publication of the drought tool research, but his work continues helping producers across the region. “Developing this tool was going above and beyond what his job required,” Ott says. Researchers continue recognizing the drought tool as an important resource for modern ranch management and forage planning.

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