Soils & Fertility

Soil has been called the “fine, thin skin” of our planet’s land. With ten of the twelve soil orders represented in the state, the diversity of soil types in Washington is renowned. A particular soil type forms in a geographical location due to the interaction of parent material, climate, aspect, vegetation, and time. For example, the highly productive Mollisols of the Palouse hills in eastern Washington formed on wind-blown deposits over tens of thousands of years. The area receives sufficient yearly rain and snow to support remarkable vegetative growth. Mollisols cover large regions of southeastern and central Washington and are also found in some of the Puget Sound lowlands.

Rainfall decreases as one moves west from the eastern edge of the Palouse, resulting in less plant growth and accumulation of organic matter. Soils under cultivation in the western Palouse and Columbian Plateau include Aridisols, light colored desert soils, and Entisols, young soils that lack horizon development. These soils are still quite productive, especially when irrigation is available. Inceptisols are another common agricultural soil in Washington, especially in the western part of the state. Though also young soils they show more horizonation than Entisols. Much of the surface of land surrounding Puget Sound is considered “young” by geologists because it was under thick sheets of ice as recently as 12,000 years ago. Before retreating, these glaciers churned and scarred the land beneath them, leaving behind glacial till, outwash, and lakes. These new surfaces served as the parent material that Puget Sound soils developed on.

Inattention to soil management likely led to the collapse of several civilizations. Today, we are asking our agricultural soils to produce more food and fiber with fewer inputs and less environmental impact. WSU continues to study soil quality across the state to develop recommendations for improved management, be it reducing soil erosion, increasing carbon storage, suppressing soil-borne diseases, providing adequate crop nutrition, or recycling organic wastes. Healthy soils are essential to sustainable agriculture and thus we need to constantly improve our management of this critical resource.

Soils & Fertility Pages