This is a scanned version of the text of the original Soil Survey report of Marion County Area, Oregon, issued September, 1972. Original tables and maps were deleted. There may be references in the text that refer to a table that is not in this document. Updated tables were generated from the NRCS National Soil Information System (NASIS). The soil map data has been digitized and may include some updated information. These are available from http://soildatamart.nrcs.usda.gov. Please contact the State Soil Scientist, Natural Resources Conservation Service (formerly Soil Conservation Service) for additional information. SOIL SURVEY OF THE MARION COUNTY AREA, OREGON BY LYNN H. WILLIAMS, SOIL CONSERVATION SERVICE FIELDWORK BY LYNN H. WILLIAMS, PARTY LEADER, AND LEROY A. DEMOULIN, HAROLD R. MANLEY, CLARENCE KNEZEVICH, W. R. PATCHING, AND CLARENCE OLDS, SOIL CONSERVATION SERVICE UNITED STATES DEPARTMENT OF AGRICULTURE, SOIL CONSERVATION SERVICE, IN COOPERATION WITH THE OREGON AGRICULTURAL EXPERIMENT STATION THE MARION COUNTY AREA consists of 544,879 acres from the sale of fruits, berries, vegetables, and specialty in the western two-thirds of Marion County, Oregon (fig. 1) . crops, although wood products are also a major source of Elevations range from about 100 feet along the Willamette farm income. The eastern part of the survey area is used River to about 5,000 feet on the forested foot slopes of the mainly for producing timber. Cascade Mountains. Salem, the State capital, is in this area. In mapping the survey area, two intensities of. soil mapping Approximately 205,841 acres in the mountainous eastern part were used (fig. 2). In the forested foot slopes of the survey of the county, mostly in national forests, is not in the area that area, soils were examined at moderate to wide intervals and was surveyed. were mapped at medium intensity. In the irrigated and dryfarmed western part of the survey area, the soils were examined at close intervals and were snapped at high intensity, or in considerably more detail than in the forested foot slopes part. Most of the soils mapped at high intensity have a narrow range of slope. To show which soils were mapped at medium intensity and which at high intensity, the kind of map symbol assigned to the soils mapped at medium intensity was made to differ slightly from the one assigned to the soils mapped at high intensity. The second letter of the map symbol is a capital letter if the mapping unit is one of those in the medium- intensity survey area. It is a small letter if the mapping unit is one of those in the high-intensity survey area. A list of all the soils in the survey area, their map symbol, and the capability unit and the woodland group to which each has been assigned can be found in the "Guide to Mapping Units" at the back of this survey. How This Survey Was Made Figure 1.-Location of the Marion County Area in Oregon. Soil scientists made this survey to learn what kinds of soil are in the Marion County Area, where they are located, and how they can be used. The soil scientists went into the area The survey area is in the central part of Oregon's Wil- knowing they likely would find many soils they had already lamette Valley. It has a modified marine climate, which is seen and perhaps some they had not. They observed the influenced by the Coast Range to the west and by the Cas- steepness, length, and shape of slopes, the size and speed of cade Mountains to the east. Climate in the foot slopes part of streams, the kinds of native plants or crops, the kinds of rock, the survey area differs considerably from that along the and many facts about the soils. They dug many holes to Willamette River, in that the amount of precipitation is expose soil profiles. A profile is the sequence of natural greater, the average temperature is lower, and the growing layers, or horizons, in a soil; it extends from the surface down season is shorter. into the parent material that has not been changed much by Farming in what is now the Marion County Area started leaching or by the action of plant roots. about 1834. The first farmers derived much of their income The soil scientists made comparisons among the profiles from raising livestock and growing small grains. Since World they studied, and they compared these profiles with those in War II, most of the farm income has been derived counties nearby and in places more distant. They classi- fied and named the soils according to nationwide, uniform The areas shown on a soil map are called mapping units. procedures. The soil series and the soil phase (13)1 are the On most maps detailed enough to be useful in planning the categories of soil classification most used in a local survey. management of farms and fields, a mapping unit is nearly Soils that have profiles almost alike make up a soil series. equivalent to a soil phase. It is not exactly equivalent, be- Except for different texture in the surface layer, all the soils of cause it is not practical to show on such a map all the small, one series have major horizons that are similar in thickness, scattered bits of soil of some other kind that have been seen arrangement, and other important characteristics. Each soil within an area that is dominantly of a recognized soil phase. series is named for a town or other geographic feature near the Some mapping units are made up of soils of different place where a soil of that series was first observed and series, or of different phases within one series. One such kind mapped. Abiqua and McCully for example, are the names of of mapping unit, called an undifferentiated group, is shown two soil series. All the soils in the United States having the on the soil map of the Marion County Area. same series name are essentially alike in those characteristics An undifferentiated group is made up of two or more soils that affect their behavior in the undisturbed landscape. that could be delineated individually but are shown as one Soils of one series can differ in texture of the surface soil unit because, for the purpose of the soil survey, there is little and in slopes, stoniness or some other characteristic that value in separating them. The pattern and proportion of soils affects use of the soils by man. On the basis of such are not uniform. An area shown on the map may be made up differences, a soil series is divided into phases. The name of a of only one of the dominant soils, or of two or more. The soil phase indicates a feature that affects management. For name of an undifferentiated group consists of the names of example, McCully clay loam, 2 to 7 percent slopes, is one of the dominant soils, joined by "and." Steiwer and Chehulpum several phases within the McCully series. silt loams, 3 to 40 percent slopes, is an example. After a guide for classifying and naming the soils had been In most areas surveyed, there are places where the soil worked out, the soil scientists drew the boundaries of the material is so rocky, so shallow, or so severely eroded that it individual soils on aerial photographs. These photographs cannot be classified by soil series. These places are shown on show woodlands, buildings, field borders, trees, and other the soil map and are described in the survey, but they are details that help in drawing boundaries accurately. The soil called land types and are given descriptive names. Stony rock map in the back of this publication was prepared from the land is a land type in the Marion County Area. aerial photographs. While a soil survey is in progress, samples of soils are taken, as needed, for laboratory measurements and for 1 Italic numbers in parentheses refer to Literature Cited, page 130. engineering tests. Laboratory data from the same kinds of soil in Three associations are in this group. Most of the soils in these other places are assembled. Data on yields of crops under defined associations are farmed, and many different crops are grown on practices are assembled from farm records and from field or plot some of them. experiments on the same kinds of soil. Yields under defined 1. Cloquato-Newberg-Chehalis association management are estimated for all the soils. Well-drained and somewhat excessively drained silty clay loams But only part of a soil survey is done when the soils have been to sandy loams; on flood plains named, described, and delineated on the map and the laboratory This association consists of nearly level and gently undulating data and yield data have been assembled. The mass of detailed soils that formed in mixed alluvium on bottom lands of the information then needs to be organized in such a way as to be Willamette River and its tributaries. The areas are traversed by readily useful to different groups of users, among them farmers, numerous meandering sloughs and overflow channels. Elevations managers of woodland, and engineers. range from 100 to 650 feet. The annual precipitation is 40 to 45 On the basis of yield and practice tables and other data, the inches, the annual air temperature is 52° to 54° F., and the length soil scientists set up trial groups. They test these groups by of the frost free season is 200 to 210 days. In areas that are not further study and by consultation with farmers, agronomists, cultivated, the vegetation is mainly alder, ash cottonwood, oak, engineers, and others, then adjust the groups according to the maple, and Douglas-fir; grasses; and wild blackberry, rose, and results of their studies and consultation.