Petrocalcic Soils Tour on the Southern High Plains of Texas and New Mexico

The MLRA 77 Soil Survey Group hosts tour on August 23-25, 2005

Natural Resources Conservation Service (NRCS) soil scientists, university educators and students are preparing to take part in a three-day tour in portions of Bailey, Dawson, Hockley, Lamb, and Lubbock Counties in Texas and in Lea and Roosevelt Counties in New Mexico.

Plans have been made for the continuation of a study of Petrocalcic soils that began in Southwestern Nebraska and Southeastern Wyoming and continued on into the Southern part of South Dakota. Small areas of Petrocalcic soils were recognized in update surveys in this part of the country a few years ago.

Since the Southern High Plains of Texas and Eastern New Mexico have by far the majority of these types of soils, soil scientists in Texas were asked to give their expertise in helping these states identify and classify the soils in their survey areas. Tour stops will include
several large open pits where “caliche gravel” is actively mined, road cuts, and soil sample sites on farms and ranches.

A petrocalcic horizon is a layer of cemented caliche (calcium carbonate) that is extremely hard and very similar to rock. These hardened layers were once a normal soil horizon that have accumulated calcium carbonate for thousands of years and cemented to form the hardened layer.

This layer of petrocalcic is also referred to as “calcrete” or “indurated caliche” and can range in thickness of 5 inches up to 30 feet thick. The presence of a petrocalcic horizon has limitations for cropland use and management and also has major limitations for building site development. These soils at the same time are a very valuable source of construction material for roads and highways and are very important to the road building infrastructure on the High Plains.
Texas and New Mexico NRCS soil scientists have recognized and mapped soils with petrocalcic horizons as early as the 1950’s. Northern states such as Nebraska with fewer acres of these soils did not recognize petrocalcic horizons in their early surveys. Instead they considered the petrocalcic as a bedrock feature.

The tour will help further the knowledge of NRCS soil scientists from Nebraska, Kansas, Wyoming, Colorado, and South Dakota and help them recognize this type of soil when mapping in their areas. This will help them make proper soil interpretations on petrocalcic soils. The tour will also benefit Texas Tech University personnel, students and newly hired NRCS soil scientists in Texas and New Mexico less familiar with these types of soils. This information will also be passed on to conservation planners who will provide NRCS users with the most current information about these soils and provide more accurate interpretations for land use and management in these areas.

For more information contact Soil Survey Project Leader, Craig Byrd at 806-791-0592.

Arvana fine sandy loam soil with a petrocalcic horizon beginning at 60 centimeters.

NRCS Soil Scientist Kelly Attebury and Dr. Wayne Hudnall, Texas Tech University soils professor work to clean off the soil pit face to expose the petrocalcic horizon.

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Petrocalcic Soils Tour on the Southern High Plains of Texas and New Mexico (1.84MB)