Oregon Soils

$7.50 MANUAL FOR JUDGING OREGON SOILS W '• ^ - Oregon State University Extension Service Extension Manual 6 September 1984 Authors This publication prepared by J. Herbert The Oregon State University Extension Huddleston, Extension soil science spec- Service provides education and informa- ialist, and Gerald F. Kling, associate tion based on timely research to help professor of soil science, Oregon State Oregonians solve problems and develop University. To simplify information, skills related to youth, family, commun- trade names of products have been used. ity, farm, forest, energy, and marine No endorsement of named products is resources. intended, nor is criticism implied of sim- ilar products that are not mentioned. Extension's agriculture program provides education, training, and technical assis- Extension Service, Oregon State Univer- tance to people with agriculturally re- sity, Corvallis, O. E. Smith, director. lated needs and interests. Major program This publication was produced and dis- emphases include food and fiber pro- tributed in furtherance of the Acts of duction, farm business management, Congress of May 8 and June 30, 1914. marketing and processing of agricultural Extension work is a cooperative program products, and resource use and conser- of Oregon State University, the U. S. vation. Department of Agriculture, and Oregon counties. Oregon State University Extension Serv- ice offers educational programs, activi- ties, and materials without regard to race, color, national origin, or sex as required by Title VI of the Civil Rights Act of 1964 and Title IX of the Education Amendments of 1972. Oregon State Uni- versity Extension Service is an Equal Op- portunity Employer. Photo and Figure Credits Plates 5, 8, 9, and 12 are reproduced Figures 4, 6, 17, 18, 19, 20, 21, 22, 23, Figure 26 is by courtesy of Billie from The Marbut Memorial Slides, and 24 are from the authors' collec- Forrest, Soil Conservation Service, slide nos. 5-10, 6-2, 6-16, and 9-1, tions. Tangent, Oregon. by permission of the Soil Science Figures 9, 10, 11, and 12 are by courtesy Figure 27 is by courtesy of OSU Agricul- Society of America. of Tom Gentle, OSU Agricultural tural Communications. Plates 2, 3, 4, 7, 10, and II are repro- Communications. Figure 28 is by courtesy of Wilbur Bluhm, duced from the William M. John- Figure 13 is reproduced from The Marbut OSU Extension Service, Salem, son slide set illustrating the United Memorial Slides, slide no. 10-4, by Oregon. States Soil Classification System, by permission of the Soil Science Soci- Figures 30 and 31 are by courtesy of Dr. permission of M. A. Fosberg, De- ety of America. Steve Sharrow, OSU Department of partment of Plant and Soil Sciences, Figure 14 is by courtesy of Herb Futter, Rangeland Resources. University of Idaho. Soil Conservation Service, Ontario, Figure 32 is by courtesy of Sandy Mac- Plates 1, 6, 13, 14, 15, and 16 are from Oregon. nab, OSU Extension Service, The the authors' collections. Figures 15, 29, and 33 are by courtesy of Dalles, Oregon. Figures 1, 5, 7, 8, and 25 were drawn by Don Baldwin, Soil Conservation Figure 34 is by courtesy of Dr. Robert Cody Bustamante, OSU Communi- Service, Enterprise, Oregon. Paeth, Department of Environmen- cations Media Center. Figure 16 is by courtesy of OSU Agricul- tal Quality, Portland, Oregon. Figures 2 and 3 are reproduced from tural Experiment Station. Soil Microbiology and Biochemistry, slide nos. 120 and 48, by permission of the Soil Science Society of Amer- ica. MANUAL FOR JUDGING OREGON SOILS IKHuddleston G. F. Kling Oregon State University Extension Service in cooperation with the Department of Soil Science September 1984 iii Contents Foreword v Chapterl. WhyStudySoil? 1 Chapter 2. The SoU We Study 3 Factors of Soil Formation 4 Processes of Soil Formation 5 From Rock to Soil 6 Chapter 3. Kinds Of Soil Horizons 7 Master Horizons 7 Special Kinds of A, B, and C Horizons 8 Transition Horizons 10 Subdivisions of Thick Horizons 10 More Than One Kind of Parent Material 10 Typical Horizon Sequences 11 Locating Boundaries Between Horizons 12 Chapter 4. Properties Of SoU Horizons 13 Color of the Soil Matrix 13 Mottling 14 Texture 16 Coarse Fragments 21 Soil Structure 21 Soil Consistence 24 Horizon Boundaries 25 Special Features of Soil Horizons 26 Color Plates 29 Chapter 5. Properties Of The Whole SoU 33 Effective Depth of Rooting 33 Available Water-Holding Capacity 34 Permeability 36 Water Erosion Hazard 38 Wind Erosion Hazard 40 Internal Soil Drainage 41 Chapter 6. Site Characteristics 45 Landform 45 Parent Materials 47 StoninessandRockiness 49 Slope 51 Aspect 52 IV Chapter?. Management Interpretations 53 Feasibility of Artiiicial Drainage 53 Suitability for Irrigation 54 Most Intensive Crop 55 Erosion Control Practice 60 Reaction Correction 63 Limitation for Septic Tank Drainfields 63 Appendixes 65 A Scorecard—Oregon State Soil Judging 67 B. How to Use Interpretation Guides 69 C. How To Set Up and Run A Soil Judging Contest 71 D. Horizon Names Used Before 1983 75 Glossary 77 Foreword Soil judging has been part of the vocational 3. We show students how to use these basic prop- agriculture curriculum in Oregon high schools erties to discover some important aspects of for over 25 years. Since 1956, the OSU Extension soil behavior, such as effective depth, water- Service and the Oregon Association of Conserva- holding capacity, susceptibility to erosion, and tion Districts have worked together to organize internal drainage class. and operate the State Soil Judging Contest. 4. We explain why soil properties and soil behav- The Extension Service has also provided educa- ior are important to soil management. tional materials for the students and conducted 5. We develop keys for students to use to relate training sessions for the instructors. For many years, soil properties to important decisions about Extension Bulletin 769, Soil Judging from the irrigation suitability, crop choices, erosion Ground Up, was used as the primary text for the control, and other questions. program. We don't expect students to memorize all the As we learned more about Oregon soils, how- factors and interactions that enter into a manage- ever, and as soil management alternatives became ment decision. We do hope, however, that they more complicated, we realized that just revising will learn how to use the keys to translate their EB 769 would not do the job. Instead a completely evaluations of profile data into solutions to real new manual was needed. problems facing modern agriculturalists. We began writing a new soil judging manual, Above all, we view soil judging primarily as an and developing a new format for judging soils, in educational program. Contests certainly add a di- 1978, when we introduced several new ideas to a mension of challenge and fun, but they are not the group of about 20 Vo-Ag instructors. They liked primary objective of the program. Instead, the the new format, and their comments were very main objective is to encourage students to investi- helpful as we wrote a draft of a new manual. We gate this fascinating resource we call soil, to dis- used this draft for 4 years while we tested new ideas cover how soils are organized into horizons, to and revised the text. learn both how to describe a few key properties of Publication of this manual would not have been soil horizons and to interpret them in terms of possible without numerous suggestions from many management practices—and to develop a sense of soil scientists and Vo-Ag instructors who have been stewardship for the soils that support them. very closely associated with the soil judging pro- Nothing would make us happier than for a gram for a number of years. To each of them, we student to challenge some of the generalized man- express our sincere appreciation. agement interpretations we describe in this manual There are several major changes in this new in terms of their relevance to his or her own soil Manual. conditions—and for the instructor to seize that 1. We encourage students to study the whole soil opportunity to do some real teaching about the profile and evaluate each of the natural soil kinds of interactions one must consider when decid- horizons present. ing how best to use the soil resources available on a 2. We stress gathering primary data on just a few given farm. When this happens, the Manual for important properties that students can deter- Judging Oregon Soils will have accomplished its mine in the field—color, texture, and structure. real purpose. Chapter 1 Why Study Soil? Soil is an essential natural resource. Without a 1,000 different kinds of soils, ranging from deep to doubt, that is the most important reason for shallow, clayey to sandy, wet to dry, nearly level to studying the soil. Nathaniel Shaler put it this way: steeply sloping. These differences are important, "Soil, ever slipping away in streams to the sea, is a because different soils require different kinds of kind of placenta that enables living things to feed management practices. upon the earth."1 Wet soils, for example, need artificial drainage. The sketch in figure 1 illustrates our depen- The correct way to drain them depends on just how dence on the soil. Unlike plant life, we human wet and how clayey they are. Many soils require beings can't manufacture our own food from the irrigation for maximum productivity. Both the four primary resources of soil, air, water, and amount of irrigation water needed and the proper sunlight. Instead, we depend completely on green method of applying it depend on a soil's permeabil- plants, which take nutrients and water from the ity rate and water-holding capacity.

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