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Producers should start planning for the 2021 growing and grazing season early

by Wyoming Livestock Roundup

By Retta Brugger and Julie Elliott

How can we make well-informed decisions for summer grazing? 

We all know 2020 was a drought year in many states. Soils are dry and will need to be refilled. 

When do we need the moisture for summer grass? How can we plan for the 2021 grazing season?   

Cooperative Extension research across the High Plains found cumulative precipitation up to 30 days before peak grass growth has the most impact. 

For eastern Colorado, peak grass growth is in June and July. This means the moisture received through mid-June sets the stage for summer grass growth. This is also true for southwestern Nebraska and western Kansas, as well as short grass prairie and sandy sites in southeastern Wyoming and the southern part of the Nebraska Panhandle.  

Where needle-and-thread grass and western wheat grass dominate the range in southeast Wyoming and the northeast Panhandle, peak growth shifts to May through early June. Thus, the critical cumulative precipitation date moves up to early May. But, it would be helpful to anticipate what might be in store before May and June.  

Results from 70 plus years of research from the Agricultural Research Service (ARS) range in Nunn, Colo. may help. It turns out long-term climate trends such as La Niña, El Niño and the Pacific Decadal Oscillation (PDO) are important. In fact, these ocean temperature cycles explain 70 percent of yearling steer weight gain differences.

Researchers used this data to create a decision tree to help them make decisions before the growing season. They watch El Niño, La Niña and PDO cycles and moisture conditions through the winter. Then, in early April, they use the decision tree as part of their stocking discussion.

Let’s take a look at the decision tree for 2021. 

The PDO is still in the warm phase and forecasters report La Niña is strong. The decision tree suggests stocking rates should be decreased moderately or relative to precipitation. Ocean activity indicates drought conditions are likely to persist. 

Another tool ranchers can use is Grass-Cast. Grass-Cast, short for Grassland Productivity Forecast, has over 30 years of historical data about weather and vegetation growth.

 It compares this data with current year precipitation to create three production forecast maps.  Each map indicates the expected grass growth based on above-normal, near-normal or below-normal summer rain.  

The first Grass-Cast maps for 2021 will be released in April. These maps can identify areas where there are early signs of opportunity or challenges. The bi-weekly maps become more accurate as more rainfall is recorded. By May 30, the average accuracy of the maps improves to 70 percent.

The decision tree, understanding timing of moisture and grass growth, as well as the Grass-Cast tool, are all useful in helping ranchers make timely grazing decisions. Responding early to drought can help protect financial and rangeland resources in the future. 

Retta Brugger is the range Extension specialist at Colorado State University and Julie Elliott is the rangeland management specialist for Colorado’s Natural Resources Conservation Service. For more information about the drought decision tool, visit For more information about Grass-Cast, visit

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