Restocking strategies during drought

Rangelands in Colorado, especially eastern and southwestern Colorado, have suffered tremendous setbacks in vegetation vigor and perennial plant growth due to drought conditions which in some areas have existed for four or more years.

Currently much of eastern and southwestern Colorado is in a continuing drought. The eastern plains are either classified as having moderate drought or severe drought. Southwestern Colorado has received moisture lately but doesn't appear to be out of the woods yet.

The onset of the drought began in 2000, causing many rangeland areas to have appreciably less forage in that year and placing stress on perennial plants. During 2001, precipitation was fair to moderate, depending on the area of the state. The year 2002 was the driest on record in Colorado. Perennial grasses, in most areas on the plains, did not grow at all that year.

Fall and winter 2003 provided marginal encouragement to range managers. Reasonable to very good spring rains provided up to a 40 to 60 percent forage crop in the 2003 growing season for those ranchers who had adjusted their stocking rates early to match the forage availability. The caveat is that most of the growth was stem and seedheads produced by plants responding to the drought stress. Many areas of rangeland lost much of the perennial grasses, especially warm season grasses. Estimates are that at least 30 to 80 percent of the blue grama died in 2002, depending on the soils and the location on the plains.

Many, if not most, ranges were very weedy in 2003. Annual weedy plants responded to the additional moisture and the lack of perennial grass competition. The weedy plants further reduced the moisture availability for perennial grasses. This means that the recovery that might have occurred in 2003 was slowed by weedy competition.

Better conditions existed in 2004 and 2005 in many locations (notably the far eastern plains and northeastern Colorado) but several areas including much of the Arkansas River Valley had severe drought in the spring and early summer of 2005. Mid-summer rains provided some much needed grass growth.

The fall and winter have been dry to very dry throughout the plains areas and extraordinarily dry in the southern mountains and the southwest. The far western portions of Colorado, especially northwestern Colorado are very dry.

The drought has caused notable declines in production from cool season grasses, such as western wheatgrass, green needlegrass, and needleandthread. Additionally, perennial warm season grasses are not fully recovered in most areas. Before the rangeland can recover, adequate soil moisture must be restored to allow plants to achieve a full array of leaves and rebuild their greatly depleted root system. This means it has to rain. In addition, the soil profile needs to retain the moisture. Moisture is critical to increase and maintain vegetation on the soil surface. This applies to plant cover and litter.

The timeline for full recovery depends on a variety of factors. Vegetation that was healthy before the drought and was used less intensely during the drought will recover far more rapidly than forage that was not afforded those breaks. Implementing a prescribed grazing management system will help provide the improved plant performance. This will help meet the land's needs. The difference may be that those rangelands that are managed well may approach 75 percent capacity in three years and may be near full capacity within five years. However, continued drought will greatly delay this recovery rate.

Those rangelands that continue to be heavily grazed will take 10 or more years to recover and will be at less than 50 percent carrying capacity in five years. Evaluating and monitoring rangeland allows ranchers to determine how the range is recovering. Data from the Non-insured Crops Assistance Program (NAP) evaluations of 2005 forage production relative to what would be normally expected is below.

Ranchers also need to stock or restock appropriately--according to the expected plant availability and to enhance plant maintenance and recovery. Remember, the "real or actual" stocking rate is the forage demand (how many animals eating how much) relative to the amount of forage on the range.

For information on how to set up a prescribed grazing management system or on how to monitor your rangeland, please contact your local USDA Natural Resources Conservation Service (NRCS) field office. Also check out the Colorado NRCS website at www.co.nrcs.usda.gov under Public Affairs News and Events to find copies of Grazing Lands Conservation Initiative Technical Notes (under Colorado Drought) that provide information on restocking strategies, prescribed grazing, and monitoring rangeland.

Date: 4/19/06

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