Tuesday, October 21, 2014

Managing Drought Risk on the Ranch

Range/Ecological Site

There are natural limits to how much forage rangelands can produce on every ranch.

Composition of range sites and the kinds of plant communities on those sites determine carrying capacity of individual pastures. Measurable differences often occur in the availability and production of forage on different range sites.

Identify Range or Ecological Sites

 

Locally Important Range Site Characteristics
  • Soil Depth, Texture, Chemistry
  • Presence of Gravel, Stones, or Rock Outcrop
  • Depth to Water Table
  • Topographic Position
  • Slope

Within a county, range sites are delineated primarily by the characteristics listed (right). Rangeland on most ranches is composed of 4 to 8 different range sites.

All characteristics listed (right) are included in the criteria used to map soils. The Natural Resources Conservation Service (NRCS) has grouped all rangeland soils into their appropriate range sites. Individual range sites are composed of multiple soil series.

Ask your local NRCS office if they can do a rangeland inventory on your ranch. This would include a ranch map showing range sites and range condition in each pasture and printed summaries of the acres, range condition, and recommended stocking rates for each range site in individual pastures. Range site information also includes common plant communities, forage production potentials, forage growth curves, and forage produced per inch of moisture.

If the service is not available, go online. Ranchers can produce individual-pasture maps with range sites at websoilsurvey.nrcs.usda.gov. The website includes a tutorial. In the NRCS vocabulary, range sites are called ecological sites. The terms are interchangeable.

Variability between Vegetative Zones

Rangelands with similar site characteristics have similar vegetation and production potential throughout a vegetation zone. In contrast, measurable differences often occur between sites with similar soil and topographic characteristics in different vegetation zones.

For example, in Nebraska a Silty range site in vegetation zone I (14"-16" precipitation) would be co-dominated by needle-and-thread, blue grama, and western wheatgrass compared to a co-dominance of big bluestem, little bluestem, and sideoats grama on a Silty range site in vegetation zone III (20"-24" precipitation). Additionally, the recommended stocking rate for Silty sites in good to excellent condition in zone I is 0.5 AUM/ac compared to 0.90 AUM/ac in zone III, an 80% increase in forage production potential.

The complete identity of a range site includes the vegetation or precipitation zone. Locally, names of range sites are based on defining characteristics, ie, Choppy Sands, Steep Adobe, Limy Upland, or Sub-irrigated. Site names may also be based on the type of vegetation, ie, Clay Savannah (scattered trees), Loamy Plains (treeless), or Claypan Prairie (grass dominated).

All characteristics listed in this table are included in the criteria used to map soils.  The Natural Resources Conservation Service (NRCS) has grouped all rangeland soils into their appropriate range sites.  Individual range sites are composed of multiple soil series.

The National Drought Mitigation Center | 3310 Holdrege Street | P.O. Box 830988 | Lincoln, NE 68583–0988
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