Range 101: Grass-Cast

Every good drought plan has key trigger dates that incorporates 1) past, current, and forecasted climatological information; 2) livestock and feed market information, 3) rangeland vegetation monitoring; and 4) a suite of management actions to bring balance between livestock demands and forage supply. The hardest part about “pulling the trigger” in the drought plan is having confidence in making the right decision. No one has a crystal ball to look into the future to have 100 percent certainty, however past experience and a buildup of scientific information and recent technological advancements can provide us with the necessary tools to make good drought management decisions.

One of those technological advancements is the new grassland productivity forecast tool called “Grass-Cast” (available online at https://grasscast.unl.edu/). This collaborative effort by USDA Agricultural Research Service, Colorado State University, National Drought Mitigation Center, University of Arizona, and the USDA Northern Plains Climate Hub provides forage productivity maps at the county level for the Great Plains and the Southwest USA. Starting on May 1st maps are generated for the upcoming growing season. The maps are updated every two weeks and to adjust seasonal estimates as more weather data is added to the models. In South Dakota, April through June rainfall is critical to producing forage on range and pasture. Since most ranchers turn out livestock on pasture in early to mid-May, having a reasonable estimate of grass production by then would be extremely helpful. By July 1st, most of the annual forage production has occurred; so waiting for rain won’t help much. Thus the best use of Grass-Cast will be in May and June.