Just as many states have official state flowers, birds, and fossils, they also have official soils. State soils are most often determined by a vote of soil scientists in the state, and, absent any political wrangling, usually represent the most productive soils and those that most closely resemble everyone’s favorite soil: loam. As mentioned earlier, loam soils are almost equal parts sand, silt, and clay.

Arizona

The state soil of Arizona is the Casa Grande series, an Aridisol. This soil is known to cover roughly 110,000 hectares (275,000 acres) but may actually cover nearly one million hectares (several million acres) of the state. This dry soil series forms in alluvium derived from weathered and eroded granite, rhyolite, andesite, quartzite, limestone, and basalt. With irrigation, these soils become productive and are used to raise vegetables, grain, and cotton.

Colorado

The Seitz series is a group of Alfisols that cover approximately 140,000 hectares (350,000 acres) of primarily mountainous terrain throughout southwestern and central Colorado. These soils support spruce and fir populations at higher altitudes, and are also home to an understory of grasses, forbs, and shrubs.

New Mexico

In New Mexico, Aridisols called Penistaja soils cover more than 400,000 hectares (one million acres). Named for a Navajo word meaning “forced to sit,” Penistaja soils are formed in mixed alluvium and aeolian material derived from sandstone and shale. They support productive rangeland and are commonly used to graze livestock.

Utah

Covering more than 80,000 hectares (200,000 acres) of southeastern Utah, Mivida soils form in warm, semiarid climates. These coarse and loamy Aridisols are home to many unique plants, including Wyoming big sagebrush, Indian ricegrass, galleta, and blue grama.