NATURAL RESOURCES INVENTORY

Soils

The geological formations described in the previous sections have provided the major sources of parent material from which the soils of Marion County have developed. Length of time the material has been exposed to weathering and variations in climate, topography, and vegetation are other factors involved in the soil development process. The many different variables involved in the development process have resulted in many different types of soil, each with different properties. The differences in properties result in differences in use, suitability and management needs, problems and potentials. Knowledge of the properties is important in determining how a soil can be best used.

To permit general analysis of the potential uses and limitations of soils for urban and rural uses, the Soil Conservation Service has grouped individual soils into associations of soils. In Marion County, the 89 individual soils identified by the Soil Conservation Service have been grouped into 11 soil associations. A soil association may be described as a group of soils that are geographically associated in a repeating pattern on the landscape. An association consists of one or more major soils and at least one minor, often contrasting, soil and is named for the major soils. The soils in one association may occur in another but in a different pattern and proportion.

This soil association information is intended only to give a very generalized picture of the soils in the County and the relationship of soils to landform areas. The soil associations are grouped into four basic landform-general soils areas which are: (1) Alluvial Bottomlands, (2) Alluvial Terraces, (3) Low Foothills and (4) Cascade Mountain Footslopes. The following is a discussion of these soil groups and their relative soil associations and is a summary of the descriptions contained in the Soil Survey for Marion County.

Soils in Marion County have been mapped, described and analyzed by the Soil Conservation Service in a soils report written jointly with the Oregon Agricultural Experiment Station. The report is written primarily as an agricultural management-oriented analysis; however, it also contains valuable data on woodland suitability, development hazards and limitations and engineering properties. This report provides generalized and detailed soil mapping and analysis by soil association and individual soil type.

Soil Associations

Soil associations are shown on the map “General Soils” and are useful for larger area analysis and planning for community development, public services, recreational facilities, wildlife areas, watershed management, etc. General soils data is used in the preparation of the Comprehensive Plan to determine land resource goals and apply use designations to the various areas of the County.

Alluvial Bottomlands – These soils are on bottomlands of the Willamette River and its tributaries and on former lakebeds. They have formed in alluvial and lacustrine materials and are nearly level. Drainage ranges from excessive to very poor but nearly one half of the acreage is well drained. Flooding is a hazard in many places and in some areas the water table is high during winter months. There are three soil associations in the group.

1.    Cloquato-Newberg-Chehalis Association. This association consists of nearly level and gently undulating soils that formed in mixed alluvium on bottomlands of the Willamette River and its tributaries. The areas are traversed by numerous meandering sloughs and overflow channels. Elevations range from 100 to 650 feet. The annual precipitation is 40 to 45 inches, the annual air temperature is 52 to 54 degrees Fahrenheit and the length of the frost-free season is 200 to 210 days. In areas that are not cultivated, the vegetation is mainly alder, ash, cottonwood, oak, maple and Douglas fir; grasses; and wild blackberry, rose and other shrubs.

Cloquato, Newberg and Chehalis soils are dominant. The rest of the association consists of small areas of Camas soils, alluvial land and of McBee and Wapato soils. All of the soils are deep and are subject to frequent overflow.

Soils of this association are used mainly for small grains, pasture, hay, orchards and grass grown for seed, but vegetables and berries are grown when some areas are irrigated. A protective cover of plants is needed on the Cloquato, Newberg and Camas soils in winter and early in spring when most flooding occurs.

Wildlife is abundant on these soils. The sloughs are inhabited by ducks, geese and fish and enough browse and other plants are available to provide food and cover for quail, pheasants, rabbits and deer.

This association is well suited to use for development of recreational facilities. It is easily accessible, is near populated areas and has readily available water for recreational, domestic use and irrigation.

Where soils are protected from overflow their engineering properties make them moderately well suited to development as sites for roads, trails and buildings. The Camas soils are an excellent source of gravel.

2.    Wapato-Bashaw-McBee Association. This association consists of nearly level soils in low, backwater areas of floodplains that are subject to frequent overflow. It is traversed by sloughs and overflow channels. The soils have formed in moderately fine-textured and fine-textured alluvium and they occur at elevations of 100 to 650 feet. The annual precipitation ranges from 40 to 45 inches, the annual air temperature is 52 to 54 degrees Fahrenheit and the length of the frost-free season is 200 to 210 days. In areas that are not cultivated, the vegetation is mainly grasses, blackberries, sedges, rushes, willows, ash trees, oaks, maples and alders.

The association occupies about four percent of the survey area. Wapato, Bashaw and McBee soils are dominant. The rest of the association consists of minor areas of Chehalis, Cloquato and Labish soils.

This association is poorly suited to use for development of recreational facilities, even though it is near populated areas and is readily accessible. The soils have engineering properties that make them poorly suited to development as sites for roads, trails and buildings. Flooding is a hazard in most years.

3.    Labish-Semiahmoo Association. This association consists of nearly level soils on the bottoms of former lakes, mainly on the Labish Bottom. Some of the soils have formed in mixed mineral and organic material and others have formed in organic material. Elevations range from about 130 to 175 feet. The annual precipitation is 40 to 45 inches, the annual air temperature is 52 to 54 Fahrenheit and the length of the frost-free season is 200 to 210 days.

Where these soils are drained they are well suited to crops and they have high value. Areas that are not drained and that are not protected are subject to flooding. In the past, onion growers risked serious losses by planting their crop in areas subject to flooding. Dikes and a pumping unit are now used to overcome this hazard.

Soils of this association are intensively managed for crops. Therefore, little food or cover is available for wildlife. The high value of the soils makes it unlikely that greater encouragement will be given to wildlife in the future.

This association is poorly suited to use for development of recreational facilities. The soils also have engineering properties that make them poorly suited to development as sites for roads, trails and buildings.

Alluvial Terraces – These soils are on alluvial terraces. They occupy a fairly broad belt that lies between areas of alluvial soils on bottomlands and areas of soils on low foothills. Silty soils occupy a large acreage and clayey and gravely soils occupy small tracts. Elevations range from 100 to 650 feet. The annual precipitation is 40 to 45 inches.

4.    Woodburn-Amity-Willamette Association. This association consists of soils that occupy areas of Willamette silts above the bottomlands of the North Santiam, Santiam and Willamette Rivers. These soils are dominantly nearly level to rolling and they have formed in silty alluvium of mixed mineralogy. Elevations range from 150 to 350 feet. The annual precipitation is 40 to 45 inches, the annual air temperature is 52 to 54 degrees Fahrenheit and the length of the frost-free season is 190 to 210 days. In areas that are not cultivated the vegetation is mainly grasses, shrubs, hardwoods and Douglas fir.

Obtaining water for irrigation is probably the most limiting factor to the use of the soils for growing vegetables and specialty crops. Nevertheless, water can generally be obtained from wells without lowering the water table. In some areas, ponds and dams have been constructed to provide places for storing irrigation water. As a result, enough water is available for irrigation in those places so that the damaging effects of dry weather in summer are overcome. In most places the soils are not well suited to use for constructing either the reservoir area or the embankment of a pond. Therefore, choosing the site for a pond requires care.

All of the soils, except the Willamette, have a perched water table in winter and early spring. For these wet soils, drainage is needed. Natural drainage ways throughout the association provide adequate outlets for artificial drainage and response to artificial drainage is good.

Abundant food and cover are available for game birds. The association is readily accessible and is close to populated areas but it is not well suited to use for development of recreational facilities. The soils have engineering properties that make them only moderately well suited to development as sites for ponds, dikes, roads and buildings.

5.    Concord-Dayton-Amity Association. This association consists of soils in nearly level areas, in depressions and in shallow, imperfectly developed drainage ways. It is mainly on divides between the drainage areas of the Little Pudding, Pudding Rivers, Champoeg and Mission Creeks. The soils have formed in silty and clayey alluvium and they occur at elevations of 125 to 350 feet. The annual precipitation is 40 to 45 inches, the annual air temperature is 52 to 54 degrees Fahrenheit and the length of the frost-free season is 190 to 210 days. In areas that are not cultivated the vegetation is mainly grasses, sedges, rushes, shrubs and hardwoods.

This association is dominated by Concord, Dayton and Amity soils. Holcomb soils make up an additional five percent and other minor soils make up the rest. The Amity soils occur at the highest elevations in the association and the Dayton soils at the lowest.

The major soils of this association are used mainly for small grains, pasture, hay and grass grown for seed. The soils contain a perched water table and water ponds on the surface during wet periods in winter and spring. Drainage is needed if crops are to grow well. Both drainage and irrigation are needed for many crops and they would benefit all crops that are presently grown.

Obtaining enough water for irrigation and other purposes is difficult in summer, but supplemental water has been provided by constructing a few farm ponds. These soils are poorly suited to use for ponds or dams, however, and natural sites for dams are few. Therefore, if a pond is to be constructed, care must be used in choosing a site.

Abundant food and cover are available for game birds. The association is readily accessible and is near populated areas but it is not well suited to use for development of recreational facilities. The soils have engineering properties that make them poorly suited to use as sites for buildings and roads.

6.    Clackamas-Sifton-Salem Association. This association consists of nearly level soils on low terraces in the Stayton Basin and along Mill Creek between Turner and Salem. It is traversed by a network of shallow drainageways. The soils have formed in gravelly alluvium and they occur at elevations of 100 to 650 feet. The annual precipitation is 40 to 45 inches, the annual temperature is 52 to 54 degrees Fahrenheit and the length of the frost-free season is 200 to 210 days. In areas that are not cultivated the vegetation is mainly Douglas fir, brackenfern, shrubs and grasses.

Clackamas, Sifton and Salem soils are dominant. Courtney soils make up nearly 19 percent and minor areas of Abiqua and Willamette soils make up the rest.

This association is moderately well suited to use for development of recreational facilities. Where adequate outlets are provided the Clackamas soils are easily drained. The Salem and Sifton soils are already suitable as sites for camping and for roads and, for the most part, construction of roads and trails is fairly easy. This association is in an irrigation district and water for recreation and domestic use is available.

Low Foothills – These soils are on low foothills, generally between alluvial terraces and the foot slopes of the Cascade Mountains. They are known as red hill soils. Most of these soils have clayey horizons below the surface layer. They are mainly underlain by basalt but the soils in rather large areas are underlain by sedimentary bedrock. Drainage is moderately good or good. Elevations range from 250 to 1,000 feet and the annual precipitation ranges from 40 to 60 inches.

Two associations are in this group. The soils of these associations are used mainly as woodland or are farmed. In the wooded areas, Douglas fir is the dominant species but oak grows on some of the soils.

7.    Steiwer-Chehulpum-Hazelair Association. This association is on low foothills that border the Salem Hills on the south and west. The soils have formed in sedimentary material. Thickness of the surface deposit varies but this material is thickest on the floor of the valley and it is thinner towards the red foothills. Elevations range from 250 to 650 feet, annual precipitation ranges from 40 to 60 inches and the annual air temperature is 52 to 54 degrees Fahrenheit. Length of the frost-free season is 190 to 210 days. In areas that are not cultivated the vegetation is mainly oak, rose, poison oak and grasses.

Steiwer, Chehulpum and Hazelair soils are dominant but the association also contains minor areas of Chehalem, Silverton and Nekia soils.

Quail, pheasant and other kinds of small game birds and game animals are plentiful. Wildlife can find abundant food and cover and they can generally obtain adequate water from streams and from irrigation ditches in adjacent associations. The numbers of small game animals and game birds could be increased by building low dams for impounding water and improving the habitat for waterfowl.

This association offers some possibilities for recreation. It contains scenic areas and favorable sites for dams and the soils are too rolling to be well suited to intensive use for cultivated crops. The soils are fairly suitable as sites for buildings and they also are fairly suitable as sites for roads and trails. Lack of adequate water for irrigation is the most limiting factor to use of these soils for some purposes.

8.    Nekia-Jory Association. This association consists of soils on uplands of the Salem and Waldo Hills. The soils in the vicinity of the Salem Hills, south of Salem, are moderately steep and have been deeply dissected by streams. Those on the Waldo Hills to the east are mostly gently sloping and moderately sloping but they are steep where breaks occur in areas dissected by the major streams. One large area of the association in the Waldo Hills extends northward from the North Santiam River to Butte Creek. It extends eastward to the foot slopes of the Cascade Mountains and parallels the foot slopes of those mountains. Between Turner and Salem this association is dissected by areas of gravelly soils on terraces along Mill Creek.

Soils of this association have formed in colluvium from basalt and tuffs and they are among the oldest in the survey area. Elevations range from 300 to 1,000 feet. The annual precipitation is 52 to 54 degrees Fahrenheit and the length of the frost-free season is 190 to 210 days. In areas that are not cultivated the vegetation is mainly Douglas fir but it includes scattered oaks and an understory of poison oak, rose and brackenfern.

Nekia and Jory soils are dominant. Minor areas of stony rock land and of Salkum, Abiqua, Waldo, Stayton, Silverton, Santiam and Witzel soils make up the rest.

Soils of this association are used mainly as woodland and for small grains, orchards, pasture, hay and grass grown for seed. Some areas that are irrigated are used mostly for specialty crops and vegetables. Moisture is adequate for growing most field crops but supplemental irrigation is needed for best returns if vegetables and specialty crops are to be grown commercially. Many areas are suitable for small ponds that could be used for storing irrigation water and a few sites are suitable for large dams. If cultivated, the steeper soils are subject to erosion but erosion is easily controlled.

Many features make this association suitable for development of recreational facilities. If large dams were constructed, water could be impounded for use for boating and fishing and also as habitat for waterfowl. The soils are suitable as sites for buildings and they are fairly suitable as sites for roads and trails. In most places groundwater is available for domestic use. Most of the areas have sites suitable for storing a limited supply of water for irrigation.

Cascade Mountain Foot Slopes – These soils are mostly steep or very steep. They are on foot slopes of the Cascade Mountains in the rugged eastern part of the survey area. Some of the soils are on ridges and others occupy long slopes that are dissected by numerous streams. The soils occur at elevations of 800 to 5,000 feet. Those at the lower elevations are clayey and those at the higher elevations are loamy. The annual precipitation ranges from 55 to 90 inches.

Three associations are in this group. They are mostly wooded but some of the areas at the lower elevations are farmed. Douglas fir and hemlock are the principal species of trees growing at the higher elevations.

9.    McCully Association. Part of this association consists of gently sloping to moderately steep soils on broad ridges. The rest consists of steep or very steep soils on breaks, where streams have deeply dissected the area. The soils have formed in till and colluvium and they occur at elevations of 800 to 2,000 feet. The annual precipitation is 55 to 75 inches, the annual air temperature is 48 to 51 degrees Fahrenheit and the length of the frost-free season is 165 to 190 days. In areas that are not cultivated the vegetation is mainly Douglas fir, hemlock, vine maple, maple and brackenfern as well as salal, snowberry and other shrubs.

The McCully soils make up about 90 percent of the acreage, Hullt soils make up about five percent, Cumley soils about three percent and other minor soils about two percent.

Soils of this association are used mainly as woodland and for small grain, pasture, hay and grass grown for seed but a few areas are used for strawberries and orchards. About half of the association is wooded or has been cut over. Moisture is adequate for growing most field crops but supplemental water is needed for vegetables and berries. Few suitable sites are available for either large or small dams.

Wildlife is abundant. Quail, pheasant and grouse are numerous and deer are so plentiful that many cultivated fields are fenced to keep the deer out. During dry summers additional water is needed for wild game birds.

This association offers good possibilities for development of recreational facilities. It contains scenic areas, is not densely populated and is adjacent to timbered uplands that are not suitable for cultivation. Fishing and hunting are available and additional facilities for boating and fishing could be provided. The soils are suitable as sites for buildings and for camping and are fairly suitable as sites for roads and trails. Water for domestic use is available from wells.

10.    Kinney-Horeb Association. Some soils of this association are on broad, irregular ridges that are dissected by streams. Others occupy long slopes that end in abrupt, short breaks leading to the basin area adjacent to streams. The soils are gently sloping to very steep and they have formed in till and colluvium. Elevations range from 1,000 to 3,500 feet. The annual precipitation is 60 to 90 inches, the annual air temperature is 46 to 50 degrees Fahrenheit and the length of the frost-free season is 120 to 165 days. In areas that are not cultivated the vegetation is mainly Douglas fir, hemlock, alder, salal, vine maple, brackenfern, swordfern and rhododendron. Kinney and Horeb soils are dominant.

Nearly all of this association is used for growing Douglas fir. Most of the association is in large tracts held by private timber companies and logging companies but a few, small, scattered tracts are Federally owned or are owned by the State or the County. A few farms, used mainly for the raising of livestock and for growing timber, are located along the North Santiam River.

Soils of this association are poorly suited to farming. The Kinney soils are too cobbly for cultivation and the growing season is shorter than in association 8. In addition, the nights are cool enough that crops do not mature until after rains have started in fall. Controlling erosion has not been difficult under past land use.

This association offers little opportunity for recreation. It is near populated areas and is accessible but because of the risk of fire, most of the area is closed to the public in summer. Furthermore, although winters are rather mild, low clouds and haze obscure the beauty of scenic areas and the snow cover is generally inadequate for winter sports. Few sites are suitable for dams of any size.

11.    Whetstone-Henline Association. This association occupies the middle slopes of the Cascade Mountains. It extends in a broad strip, probably to the foot slopes of Mt. Jefferson, which lies east of the survey area. The association is characterized by sharp, knife-like ridges having side slopes that plunge abruptly to basins or bottoms along streams. The soils have formed in colluvium and till. Elevations range from 3,000 to 5,000 feet. The annual precipitation ranges from 70 to 90 inches, the annual air temperature is 41 to 45 degrees Fahrenheit and the length of the frost-free season is 90 to 100 days.

All of this association is in large timbered tracts that are privately owned, Federally owned or State owned. The association is covered with snow in winter and spring and the cool climate and large amount of moisture make use and management of the soils difficult. None of the acreage is cultivated, for the soils are too stony and steep for cultivation. Under proper management the soils are moderately well suited to Douglas fir, silver fir and hemlock.

This association offers only limited opportunities for recreation. The area is closed to the public during the time when fires are most prevalent. In winter it is mostly inaccessible, although a few logging roads and fire roads have been constructed along the larger streams. The snow cover is adequate for winter sports, but the terrain is unsuitable in most places.

Individual Soil Type Analysis

All of Marion County west of the National Forest lands is included in the soil report. In addition to the generalized soil analysis, the report is primarily oriented to the mapping and analysis of individual soil types. Each of the 89 soil types have separate and distinct characteristics that result in different use management considerations. Individual soil type data are used extensively and are important criteria in making decisions on area-wide planning as well as specific property land use change applications. The Soil Conservation Service report contains several analyses of each soil’s capability to be used for agriculture, forestry, development related activities, as well as a description of the engineering properties of each soil. The following is a discussion of the soil suitability for agricultural use. For details on this analysis see the report text.

Soil Suitability for Agriculture

Soil suitability for agricultural use naturally varies from place to place and from soil type to soil type. Knowledge of the potentials and limitations of each soil for agricultural use (as well as for other uses) is quite important in resource planning. The total soil acreage available for agricultural use is being reduced in Marion County. Therefore, common sense indicates that conservation of the “best” agricultural soils is an extremely important objective. Another equally important objective is the conservation of the “best” agricultural areas; that is, areas which not only contain soils of high productivity and natural agricultural suitability, but also are well suited in relation to necessary transportation facilities, processors, labor supply, water, etc., and are relatively free from nonfarm uses which would interfere with efficient farming practices. The agricultural land preservation issue is discussed later in this report and in the Plan Policy Document.

As part of the County soil survey, each soil in the County has been analyzed and classified according to its suitability for agricultural use. The Soil Conservation Service classification system uses eight land capability classes. Soils categorized within each class exhibit the same general potential and limitations for sustained production of those common cultivated crops, which do not require specialized site conditioning or site treatment. The risk of soil damage or limitation in use becomes progressively greater from Class I to Class VIII. Within each class, subgroups are established according to the major causes of limitation; these include (e) for erosion hazard because of slope or textural quality, (w) for wetness because of drainage conditions or overflow, and (s) for root zone limitations because of soil qualities.

The soil types have been depicted on the map “Soil Suitability for Agriculture,” in three categories of soil class. The first two groups include soil Class I through Class IV which includes the most productive soils for agriculture. The third group of Class V through Class VIII is the marginal or less productive soil types and is generally considered nonfarm lands. There are no soils in Marion County in land capability Class V. Some soils in the national forest area of the County are most likely Class VIII soils, but information is not currently available for that area. The following discussion from the Soil Conservation Service general soils report describes the land capability classification system used for Marion County.

Class I soils have few limitations that restrict their use and are excellent for cultivated crops. Class II soils have some limitations that reduce the choice of plants or require moderate conservation practices and are good for cultivated crops. Class III soils have severe limitations that reduce the choice of plants or require special conservation practices or both. They are fair for cultivated crops. Class IV soils have very severe limitations that restrict the choice of plants, require very careful management, or both. They are poor for cultivated crops. All four capability classes also can be used for pasture, woodland, and wildlife food and cover. Class VI soils have severe limitations that make them generally unsuited for cultivation and limit their use largely to pasture, woodland, or wildlife food and cover. Physical conditions are such that pasture and woodland improvements can be made if needed. Class VII soils have very severe limitations that make them unsuited for cultivation and that restrict their use largely to grazing, woodland or wildlife. Physical conditions are such that it is impractical to apply improvements. Soils and landforms in Class VII have limitations that prohibit their use for commercial plant production and restrict their use to recreation, wildlife, water supply and aesthetic purposes.

The SCS land capability classification system is applied to and categorizes individual soils, not soil associations. Consequently, in order to map land capability class information based on soil associations, it was necessary to convert and generalize the information on individual soils. The “Soil Suitability for Agriculture” map shows soil suitability for agriculture as they have been grouped into the expanded soil associations, numbering 23. This map provides an overview of agricultural suitability for generalized planning purposes only. For a more detailed analysis of individual soil class for agriculture, the County Planning Department has developed subarea soil maps that are on file in that office.

The LCDC Agricultural Lands Goal No. 3 relies very heavily on the agricultural soil classification as the basis of the County’s agricultural lands preservation program.

Though the Marion County Soil Survey has mapped individual soil types at a property-specific scale, it may occasionally be necessary to have a more specific analysis done for an individual parcel when a specific development proposal is made. Soil types can be intermingled to the point that the Soil Conservation Service survey may not have shown them individually and aggregated them under one soil type. The mapping survey was not accomplished on the basis of on-site survey, therefore, a more specific survey may reveal a more refined and detailed soil pattern.

When an individual wishes to obtain a detailed soil study it will be necessary to consult with a reputable, qualified soil scientist to perform the study. Marion County will rely on the Soil Conservation Service representatives to help determine the adequacy of any detailed study.