Grass-Cast helps producers gauge grassland production

“All spring we wait and we watch out our windows and we wonder if there’s going to be enough grass to support our livestock out on our native range lands,” Dannele Peck said.

Peck, an Agriculture Research Service economist and director of the U.S. Department of Agriculture’s Northern Plains Climate Hub, explained Grass-Cast during a recent webinar hosted by USDA Climate Hubs, National Drought Mitigation Center, NOAA and the National Integrated Drought Information System.

Grass-Cast is an effort and outcome of dozens and dozens of people from academia to NDMC and other researchers, she said. ARS and other USDA agencies have played important roles, too, in the development of the tool.

“In the past, the best thing we could offer our range land managers and our ranchers for a forecast to try and anticipate what might happen during the upcoming growing season was our seasonal outlooks—from our friends at NOAA,” Peck said.

Many ranchers would ask, “but what does this really mean for me as a rancher or as a range manager?”

“To be honest for a very long time I didn’t have a great answer,” she said.

Ranchers and range managers were left to translate the maps and forecasts themselves.

“We all know that the relationship between precipitation and how much grass grows out on our native range lands is pretty complicated,” Peck said. “So we were asking them to do a lot in that translation, but we realized we, as scientists, could take that extra step for them.”

And that’s when the idea of Grass-Cast was born. The team in charge is able to take weather observations to date and produce forecasts for growth during the rest of the growing season based on weather forecasts.

“We put those together to try and give you an estimate of how well we expect grassland productivity to be in your area,” she said.

Peck said they put the observed weather, forecasted weather for the upcoming growing season into their grassland simulation model. This takes the daily weather information and translates it into how much evapotranspiration is expected to happen over the upcoming growing season.

“Evapotranspiration is how much water is moving up through the roots of that plant and out its leaves and out of the soil,” she said. “It relates really closely to how vigorously our range land plants are growing how green are they and healthy and robust versus how kind of brown and crunchy they might be if it’s hot and dry out.”

One last step in the process helps translate the information into something ranchers really care about—pounds per acre of vegetation for the season.

“It’s what makes a part possible to produce Grass-Cast for a bigger region,” she said. “But we don’t just care about greenness.”

They put the precipitation forecasts into three different scenarios, allowing them to do some planning. The scenarios include above normal, near normal and below normal precipitation levels. Feedback helped them perfect the map.

Users choose the location they’re interested in, and the legend on the side gives them how many pounds per acre, compared to average, might be available during the upcoming season. For example, if the precipitation is above normal during the entire growing season, Peck expects there to be 5% to 15% more pounds per acre in that area’s long-term average.

“What if precip for the upcoming growing season is only near normal?” she said. “If (your) area were to get near normal precipitation from the rest of the growing season, our model suggests that they should expect 15% to 30% less pounds per acre than average.”

And “what if the spigot turns off for the whole growing season?”

“That is the scenario that none of us like to think about,” she said. “But it’s, unfortunately, kind of been the reality this summer. If it’s below normal precip for the rest of the growing season, our models are suggesting that this area should expect 30% less pounds per acre, or worse.”

The maps get updated every two weeks throughout the growing season, and are posted on the Grass-Cast website, https://grasscast.unl.edu/.

Peck said the Grass-Cast tool isn’t perfect.

“It’s a model. It has limitations, and so it’s really important that you continue to use other sources of information and to take your local context into consideration,” she said. “For example Grass-Cast can’t tell the difference between palatable grass species that your livestock are going to enjoy eating and get fat and happy on versus weedy unpalatable species like cheat grass.”

Peck said the only thing Grass-Cast knows is that your pasture is below average production for this year.

“You have to know the conditions in your pasture, and also need to know whether your pasture tends to be more or less vulnerable to drought than pastures in your local area,” she said.

If you’re a rangeland manager or rancher facing drought conditions, it’s time to be making some decisions or already be taking steps to deal with having much less forage, Peck said. She’s already had reports of producers weaning calves early and reducing herd sizes.

“If you’re a yearling operation or a stocker operation, you have more flexibility,” Peck said. “You get to sell those yearlings first before you have to start dipping in and selling that valuable breeding stock.”

Even though she’s an economist, she believes producers need to start thinking about flexible stocking options for yearlings or making the cow-calf herd smaller.

“Those yearlings you can flex up and down in response to the grass availability,” she said. “This doesn’t apply to all regions, but there’s lots of other ideas out there.”

Peck said there’s a number of resources available from the NDMC, USDA and Extension people regarding drought and changes in forages.

“There’s lots of opportunities out there to try and help make your ranch or your range land more resilient for the next drought,” she said.

Kylene Scott can be reached at 620-227-1804 or [email protected].