Source: North Dakota State University
Balancing your forage resources to ensure you are not overdrawing from your supplies is critical to the long-term profitability of your ranch, a North Dakota State University Extension expert says.
“The key is ensuring that the stocking rate does not exceed pasture carrying capacity, as overgrazing can cause long-term reductions in forage production, leading to decreased livestock production,” says Miranda Meehan, Extension livestock environmental stewardship specialist.
The stocking rate is the number of specific kinds and classes of animals grazing or using a unit of land for a specific time period. When setting the stocking rate, knowing the carrying capacity of the pasture is critical, Meehan notes. Carrying capacity is a measure of how much forage a grazing unit has and is able to produce in an average year.
“We are well into the growing season, and as it progresses, the potential for timely precipitation and forage growth decreases,” she says. “By July 1, cool-season-dominated grasslands have produced 90% of their forage, whereas this is delayed to Sept. 1 for warm-season-dominated grasslands.”
Now is the time to evaluate your potential for forage production for the current grazing season.
“To accurately do this, it is important to understand the relationship between precipitation and forage production in your area,” Meehan explains. “In North Dakota, April-June precipitation is a good predictor of annual forage production in mixed-grass prairies. The best predictor in warms-season prairie is May-July precipitation.”
Due to the relationship between precipitation and forage production, precipitation during these months can be used to predict potential deficits in forage production. For example, if precipitation during this period is 75% of normal, producers can expect forage production to be 25% lower than normal. These predictions of production then can be used to make forage and grazing management decisions earlier in the grazing season that balance resources and reduce risk.
Ranchers can use precipitation records for their location to predict the potential for forage production. This can be done by comparing the current year’s precipitation during this time period to the median precipitation for the last 30 years at your location. You can use this information to calculate the probability of receiving adequate precipitation for forage growth.
“We recommend using the last 30 years to account for the large amount of variation between years,” Meehan says.
For example, if your location typically receives 6.88 inches of precipitation in April-June and you received 2.5 inches in April and May, you will need to receive 4.38 inches in June to achieve normal forage production.
“You can determine the probability that you will receive adequate precipitation to achieve normal forage production levels by assessing the number of times you have received 4.38 inches in June in the last 30 years,” Meehan says. “You have received 4.38 inches 12 times in the last 30 years, so there is a 40% chance of receiving adequate precipitation.”
Other tools that can aid in predicting forage production potential include weather prediction models and Grass-Cast. Grass-Cast is a forage production prediction tool developed by the U.S. Department of Agriculture’s Agricultural Research Service, Colorado State University, the National Drought Mitigation Center, University of Arizona and the USDA Northern Plains Climate Hub. This tool compares seasonal estimates to a 34-year average to develop county-level forage production maps for three precipitation scenarios: above normal, near normal and below normal, which are updated every two weeks.
“The ability to better predict annual forage production allows ranchers to adjust their forage withdrawals accordingly to ensure that the stocking rate is not exceeding the carrying capacity,” Meehan says. “However, these are just estimates and there are several other factors that influence carrying capacity, including growing conditions last year, grazing history and, of course, stocking rate.
“Predicting potential forage production and monitoring available forage to ensure your livestock are not overdrawing from your forage account is critical for the environmental and economic sustainability of your ranch,” she adds.