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98
<br />If this unit is used for urban development, the main
<br />limitations are the moderate shrink-swell potential and
<br />moderately slow permeability. The moderate shrink-swell
<br />potential may limit use of the unit for basements and
<br />certain other structures. In summer, irrigation is required
<br />for lawn grasses, shrubs, vines, shade trees, and
<br />ornamental trees.
<br />Septic tank absorption fields are suited to this unit.
<br />This map unit is not assigned a capability
<br />classification.
<br />77B-Marcola cobbly silty clay loam, 2 to 7
<br />percent slopes. This deep, moderately well ,drained soil
<br />is on fans. It formed in alluvium and colluvium derived
<br />from mixed sedimentary and volcanic rock. Areas are
<br />fan-shaped and are 3 to 60 acres in size. The vegetation
<br />in areas not cultivated is mainly Douglas-fir, Oregon
<br />white oak, shrubs, and grasses. Elevation is 400 to 1,200
<br />feet. The average annual precipitation is 40 to 60 inches,
<br />the average annual air temperature is 50 to 54 degrees
<br />F, and the average frost-free period is 165 to 210 days.
<br />Typically, the surface layer is very dark brown cobbly
<br />silty clay loam about 15 inches thick. The upper.l8
<br />inches of the subsoil is dark brown very cobbly clay and
<br />extremely cobbly clay, and the lower 27 inches is
<br />multicolored, mottled extremely cobbly clay.
<br />Included in this unit are small areas of McAlpin and
<br />Salem soils and Dixonville, Nekia, and Philomath soils on
<br />knobs and toe slopes. Included areas make up about 15
<br />percent of the total acreage.
<br />Permeability of this Marcola soil is slow. Available
<br />water capacity is about 6 to 9 inches. Water supplying
<br />capacity is 18 to 24 inches. Effective rooting depth is
<br />limited by a high water table that is at a depth of 3.5 to
<br />4.5 feet from November to May. Runoff is medium, and
<br />the hazard of water erosion is moderate.
<br />This unit is used for small grain, hay, pasture,
<br />homesites, and Christmas tree production.
<br />This unit is better suited to pasture and small grain
<br />than to most other crops. Erosion can be reduced if fall
<br />grain is seeded early, stubble-mulch tillage is used, and
<br />tillage and seeding are on the contour or across the
<br />slope. Also, waterways should be shaped and seeded to
<br />perennial grass. Returning crop residue to the soil or
<br />regularly adding other organic matter improves fertility,.
<br />reduces crusting, and increases the water intake rate.
<br />Use of proper stocking rates, pasture rotation, and
<br />restricted grazing during wet periods helps to keep the
<br />pasture in good condition and to protect the soil from
<br />erosion and compaction.
<br />Grain and grasses respond to nitrogen; legumes
<br />respond to phosphorus, boron, sulfur, and lime; and
<br />vegetables and berries respond to nitrogen, phosphorus,
<br />.and potassium.
<br />If this unit is used for recreational development, the
<br />main limitations are cobbles and pebbles in the surface
<br />layer, clay content, and slow permeability. The unit is
<br />Soil Sunray
<br />suitable for paths and picnic areas during the drier part
<br />of the year.
<br />Population. growth has resulted in increased
<br />construction of homes on this unit. The main limitations
<br />are the slow permeability, moderate to high shrink-swell
<br />potential, and low soil strength. If buildings are
<br />constructed on the soil in this unit, properly designing
<br />foundations and footings and diverting runoff away from
<br />buildings help to prevent structural damage as a result of
<br />shrinking and swelling. Buildings and roads should be
<br />designed to offset the limited ability of the soil to support
<br />a load. Roads need the maximum amount of base rock
<br />to prevent cracking and separation as a result of low soil
<br />strength and shrinking and swelling.
<br />Landscaping plants that tolerate a seasonal high water
<br />table and droughtiness should be selected if drainage
<br />and irrigation are not provided.
<br />This map unit is in capability subclass IVs.
<br />78-McAlpin silty clay loam. This deep, moderately
<br />well drained soil is on flood plains and alluvial fans: It
<br />formed in fine textured. mixed alluvium. Slopes are 0 to 3
<br />percent. Areas are elongated in shape and are 3 to 100
<br />acres in size. The vegetation in areas not cultivated is
<br />mainly Douglas-fir, ponderosa pine, red alder, Oregon
<br />ash, shrubs, and grasses. Elevation is 300 to 1,000 feet.
<br />The average annual precipitation is 40 to 60 inches, the
<br />average annual air temperature is 52 to 54 degrees F,
<br />and the average frost-free period is 165 to 210 days.
<br />Typically, the surface layer is dark brown silty clay
<br />loam about 14 inches thick. The upper 8 inches of the
<br />subsoil is dark brown silty clay, and the lower 38 inches
<br />is brown, mottled silty clay and clay.
<br />Included in this unit are small areas of Abiqua and
<br />Waldo soils, Riverwash, and Fluvents. Included areas
<br />make up about 15 percent of the total acreage.
<br />Permeability of this McAlpin soil is moderately slow.
<br />Available water capacity is about 8 to 20 inches. Water
<br />supplying capacity is 18 to 24 inches. Effective rooting,
<br />depth is limited by a high water table that is at a depth of
<br />2 to 3 feet from November to March. Runoff is slow, and
<br />the hazard of water erosion is slight. The soil is subject
<br />to rare periods of flooding.
<br />This unit is used mainly for cultivated crops. It is also
<br />used as woodland and for wildlife habitat and recreation.
<br />This uriit is suited to cultivated crops. In summer,
<br />irrigation is required for maximum production of most
<br />crops. Sprinkler irrigation is a suitable method of applying
<br />water. Tile drainage on this unit improves productivity
<br />and facilitates management. Good outlets generally are
<br />available.
<br />Returning all crop residue to the soil and using a
<br />cropping system that includes grasses, legumes, or
<br />grass-legume mixtures help to maintain fertility and tilth.
<br />Grain and grasses respond to nitrogen; legumes respond
<br />to phosphorus, boron, sulfur, and lime; and vegetables
<br />
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