Mivida Soil Series

Mivida soil is a desert soil with a calcium problem — in the best agricultural sense. Thousands of years of scarce rainfall have leached calcium carbonate downward from the surface and deposited it as a white, chalky layer in the subsoil. That calcic horizon is the defining feature of the Mivida series and sets it apart from the younger desert soils around it.

The soil developed from eolian sand and alluvium derived from Jurassic and Cretaceous sandstone — the ancient desert and sea-floor rock that forms the canyon walls and mesa caps of eastern Utah. Very little rain falls here: 8 to 12 inches per year, most of it from summer monsoon thunderstorms and winter snow.

Soil scientists at the USDA Natural Resources Conservation Service selected the Mivida series to represent Utah because it is the most extensive and representative soil on the Colorado Plateau — the canyon country of eastern Utah that covers more of the state than any other single landscape.

The series is named after the Mivida Mine, a uranium mine in San Juan County in southeastern Utah. Uranium mining shaped the economy of San Juan County through the mid-twentieth century, and the mine site gave its name to the soil series first described in that area.

The Mivida series is recognized by the USDA as Utah's state soil. It was selected because the Colorado Plateau — where Mivida soil is most extensive — covers roughly half of Utah's total land area and is the most geologically distinctive region in the state.

Dig into Mivida soil and the surface is reddish brown and gritty — fine sandy loam that crumbles easily in the dry air. A few inches down, the color intensifies slightly as a weak cambic horizon develops. Below that the soil gradually pales as calcium carbonate accumulates, and in the main calcic layer you can see white powdery coatings on the sand grains and pebbles. Deep in the profile the soil returns to a clean pinkish-tan — the wind-deposited sandstone sediment it all came from.

Mivida soil grows on the flat to gently sloping mesa tops, structural benches, and alluvial fans of the Colorado Plateau in eastern Utah — the red-rock country carved by the Colorado River and its tributaries. Elevations range from 4,500 to 7,000 feet, where the semi-arid climate delivers 8 to 12 inches of precipitation per year.

San Juan County holds the type location and the largest concentration of Mivida soil. The series also extends into Emery, Wayne, and Grand counties — the heart of Utah's canyon country.

Cattle ranching is the primary land use on Mivida soil. The mesa tops and canyon benches support sparse but reliable forage: Indian ricegrass, galleta grass, and blue grama provide year-round grazing for cattle and sheep, supplemented by fourwing saltbush and Mormon tea on the drier sites.

Pinyon pine and Utah juniper form the characteristic woodland canopy over Mivida soil where elevation and precipitation allow. This pinyon-juniper zone covers millions of acres of Utah's canyon country and provides habitat for mule deer, pronghorn, and the pinyon jay. Piñon nuts were a critical food source for Ancestral Puebloans and continue to be harvested by Native communities.

Dryland winter wheat is grown on Mivida soil in a few areas where annual rainfall reaches the upper end of the range. Hay and alfalfa require irrigation but are grown in valley bottoms adjacent to Mivida uplands. Much of the San Juan County landscape underlain by Mivida soil was also historically used for uranium and oil exploration.