This year's drought in the Southern Plains region was historic by any measure, but even in more normal times, drought is a common, recurring challenge for beef producers. And while most droughts are relatively short-term events, how a rancher responds can influence their long-term impact on the ranch and its forage resource.
University of Nebraska range-management specialist Jerry Volesky, PhD., notes that fluctuations in precipitation can dramatically influence forage production on a ranch. Data from the University's Bartle Brothers Ranch in the east-central Sandhills show upland range annual production ranging from 880 pounds per acre in 2002 – a moderate drought year – to as much as 2,360 pounds per acre during 2009.
Clearly the ideal stocking rates during those years would have been significantly different, but stocking rates often are based more on averages, rather than actual forage production. Volesky says 12 years of data from the same location show that annual forage production averages 1,770 pounds per acre, which would support a stocking rate of 0.75 animal-unit months (AUM). Most years though, the actual production is well below or above the average. The best stocking rate based on actual production would have ranged from a low of 0.37 AUM in 2002 to 1.11 AUM in 2009.
Volesky cites another study on mixed-grass prairie in eastern Wyoming where forage production ranged from 100 pounds per acre in a drought year to over 2,000 pounds per acre in a wet year.
Timing of precipitation also plays an important role in forage production, with the ideal timing depending on the location, soil type and mix of plant species on the ranch. Knowledge of these key times, coupled with precipitation records, can help ranchers make stocking decisions early to avoid overgrazing. In the Nebraska Sandhills, where warm-season grasses dominate, Volesky says precipitation during May, June and July correlate best with seasonal forage production. In mixed-grass environments in western South Dakota, research shows that April, May and June precipitation is the best predictor of production.
Volesky notes that drought affects the nutritional value of forage as well as total production, with plants reaching maturity earlier in the season and declining in nutritional value more quickly. In the Sandhills region for example, the average crude protein (CP) content of native range on June 7 is 12.3 percent. During the drought year of 2002, researchers measured CP levels averaging 12.7 percent on June 7. But by July 30, 2002 when CP averages 10.3 percent, CP had declined to 5.9 percent in response to dry conditions.
Total digestible nutrient (TD) content for the same area averages 69 percent for June 7 and 54 percent for October 14. During the drought year of 2002, TDN averaged 53 percent on June 7 and 48 percent on October 14.
If drought conditions begin to take hold during the season, Volesky suggests planning for options to reduce grazing pressure and nutritional stress in the cow herd. Early weaning is one good option, as it reduces nutrient requirements for cows as well as the forage calves would otherwise consume. For every day earlier ranchers move weaning dates, they save about 10 pounds of forage per calf, or about 40 percent of the daily requirements for cows. Returning cows to good body condition after weaning benefits fertility and calving rates.
In addition to early weaning, Volesky stresses keeping the cow inventory at least current with normal culling rates. If drought becomes significant, consider culling deeper and earlier, possibly selling cow-calf pairs early in the season. He also suggests supplementing distillers" grains where appropriate in pasture cattle, which can reduce their forage intake.
For operations with land that could be planted with alternative forages, Volesky points out that warm-season forages such as sorghum, sudangrass or millet can be planted during late spring or summer for late summer or fall grazing. Producers can plant cool-season small grains such as winter wheat, oats or rye in late summer for fall and spring grazing. He notes that seed supplies for some of these crops are short, particularly sorghum, sudangrass and millet for which much of the U.S. seed production is in areas stricken with drought last year.