ppchap3

THE NATURE AND PROPERTIES OF SOILS, 13/e Nyle C. Brady and Ray R. Weil

©2002 Pearson Education, Inc. Upper Saddle River, New Jersey 07458

Chapter 3 Soil Classification

Roy Simonson investigates a soil. (R. Weil)



Individual Soils

• Pedon – A hexagonal column of soil measuring from 1 to 10m2 in top surface area. A pedon is the basic sampling unit used in soil surveys.

• Polypedon – An essential soil individual, comprising an identifiable series of soils in an area. It is made up of multiple pedons and has distinctive characteristics that differentiate it from surrounding polypedons.

• Series - A soil series is a class of soils and the basic units used to classify soils. Nearly 19,000 soil series in the US.



Figure 3.1



Soil Classification• Soil Taxonomy – This formal term refers to the system of

classification developed by the USDA Soil Survey. Based on soil properties as they are found today.

• Diagnostic Soil Horizons – Reflects a distinctive property (color, texture, structure, consistence, porosity, moisture) or a dominant soil process. The presence or absence of wither of these diagnostic horizons usually distinguishes a soil for classification.

• Epipedon – (literally “over the soil”) A diagnostic horizon at the surface where most of the rock structure has been destroyed. It may extend downward through the A horizon, even including all of an illuviated B-horizon.





Figure 3.3



Figure 3.4



Figure 3.5



Figure 3.7





Figure 3.8





Figure 3.9





World Distribution of Soil Orders



Figure 3.11



Map 3.5



Entisol



Figure 3.12



Entisols



Map 3.6



Inceptisol



Inceptisol



Map 3.7



Andisol



Figure 3.13



Andisol



Map 3.8



Gelisol



Map 3.9



Histosol



Figure 3.16



Map 3.10



Aridisol



Figure 3.17

(a) (b)



Figure 3.18



Map 3.11



Figure 3.19



Figure 3.20



Figure 3.21



Map 3.12



Mollisol



Figure 3.22



Figure 3.23

(a)

(b)



Mollisol

Typic Argiustolls with a calcic horizon overlain by a Mollic epipedon



Map 3.13



Alfisol



Figure 3.24



Figure 3.25



Alfisol



Map 3.14



Ultisol



Figure 3.26



Typic Hapludult

Ultisol



Map 3.15



Spodosol



Figure 3.27



Spodosol

Humic Cryorthod



Map 3.16



Oxisol



Oxisol



Figure 3.30



Figure 3.31









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