Soils in the Holdrege series are recognized by features of their "profile" created by horizontal layers that are the result of the prairie environment. Holdrege soils exist on 1.8 million acres of landscape in central Nebraska that is the result of geologic processes operating over tens of thousands of years. The soils formed under mixed grasses, in a climate where moisture stress is common, but where enough movement of water through the profile has resulted in downward movement of clays and lime. These processes have led to a soil with thick, dark-colored topsoil, clay-enriched subsoil, and a substratum that contains free lime.
Holdrege soils were initially found during the soil survey of Phelps County in 1917. Their natural fertility, desirable tilth, and the landscape on which they exist join with irrigation and skillful farm management to provide a valuable agricultural resource. The legislature designated Holdrege Silt Loam as the Nebraska State Soil in 1979. This is a soil of which Nebraskans can be proud and one that we should conserve because it must sustain our agriculture for generations to come.