Alderwood
Gravelly Sandy Loam

Mapping Symbols and Slope Classes: 
AgB: 0 to 6% Slopes
AgC: 6 to 15% Slopes
AgD: 15 to 30: Slopes

The Alderwood series consists of moderately well-drained soils underlain by consolidated glacial till (hardpan) at a depth of 24 to 40 inches. Alderwood soils formed in glacial deposits under conifers. They occupy upland areas at elevations between 100 and 800 feet. The annual precipitation is 35 to 60 inches, mostly rainfall between October and May. The frost-free season is 150 to 200 days.

Typical Profile:
Depth from Surface:
0 to 27 Inches: Dark brown gravelly sandy loam. May be thinner in depth.
27 to 60 Inches: Grayish brown weakly to strongly consolidated glacial till (hardpan).

Permeability: Rapid in surface layer and subsoil above hardpan material. Very slow in the hardpan.

Rooting Depth: Roots penetrate easily to the hardpan layer. Roots have difficulty penetrating into the hardpan.

Depth to Seasonal High Water Table: 2 to 3 feet

Available Water Holding Capacity: Seasonally low (Summer) to seasonally high (Winter)

Runoff Potential: Slow to medium

Erosion and Slippage Hazard: Moderate, ranging to severe on steeper slope phases

Use and Management: Primary uses are for timber, pasture, berry production, row crops, and urban development. Pasture forage yields are 2.0 tons/acre/year. Low fertility and summer droughtiness are limiting factors. Douglas-fir, Western Red Cedar, Western Hemlock, Red Alder, and Bigleaf Maple are important tree species on all slope classes. Black Cottonwood can also be an important species on the AgB slope class. These soils have moderate to severe limitations on equipment use for site preparation and timber harvest. These soils have moderate to severe limitations on recreational and engineering uses due to their seasonal high water table and very slow permeability in the hardpan layer for all slope classes and erosion/slippage potential in steeper classes. Alderwoods which are farmed should be kept in permanent type crops 75% of the time, with not more than one consecutive year of row crops or small grains between permanent seedings. Crops respond well to applications of manure, fertilizer, and supplemental irrigation.

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