Soil types in the United States is broken down into 12 orders. The Natural Resource Conservation Service breaks each of these 12 orders down into suborders. Of the 12 soil orders, four encompass tropical qualities and offer tropical soil sub orders, according to the Natural Resource Conservation Service.
Histosols are made up of four subsoil groups: fibrists, saprists, folists and hemists. Saprists, the tropical soil subgroup from the histosols, are generally found in Southern areas of the country, primarily Florida. The soil's organic material is well decomposed, making it a thriving source for most plant types. Areas of saprists soil is common in the Atlantic and Gulf Coast regions. The soil supports vegetation growth and serves as a wildlife habitat as well.
Andisols encompass seven different soil subgroups. The subgroups ustands and udands offer the tropical soil conditions that the other andisols do not. Both are found in portions of Hawaii and hold water into the soil. The ustands form mostly under forest or savanna vegetation and is used for cropland, pasture or urban development. Udands are dominant in Western Washington and Oregon, as well as Hawaii. This soil is mostly found in forest regions but also has been cleared for used as cropland and pastures.
Ultisols offer five soil subgroups, one of which, aquults, carries the tropical soil qualities. Aquults is found along the eastern coastline. This soil is primarily located in areas there the ground water is close to the surface along coastal plans. It supports forest vegetation.
Oxisols carry four soil subgroups, all of which carry some tropical qualities. Aquox is a wet soil that is found only in Hawaii and Puerto Rico. Seed crops are very difficult to grow in this soil due to its high moisture content. Terrox soil is a rare soil in the United States and is an oxisol soil found in arid regions. It is very uncommon. Udox and ustox soils both are located in Hawaii, Puerto Rico and Guam. Udox soil is supportive of continuous rain fed crop planting, while ustox can only support one rain fed crop per year due to its extensive moisture.