The pedon is the individual classified with Soil Taxonomy. PedonĪ pedon is a three-dimensional body of soil that has sufficient area (roughly 1 to 10 m 2) and depth (up to 200 cm) to be used in describing the internal arrangement of horizons and in collecting representative samples for laboratory analysis (see chapter 4). Other more specific terms are described or defined in the following sections. This section describes several of the general terms for internal elements of the soil. Chapter 11 discusses soils heavily impacted by human activity. Chapter 10 provides information specific to describing subaqueous soils. Chapter 6 discusses the use of proximal sensors to measure some soil properties quickly and efficiently at field and larger scales by using field-based electronic technology. Chapter 2 provides information related to describing the site surrounding the soil profile. The information in this chapter, which focuses on the standards and guidelines for describing a soil profile in the field, is complemented by that provided in chapters 2, 6, 10, and 11. The kind of exposure (e.g., bucket auger, push tube, small hand-dug pit, backhoe pit, road cut, etc.) should be identified in the soil description. Horizons are studied in both horizontal and vertical dimensions. Complete study of an entire pedon requires the exposure of a vertical section and the removal of horizontal sections layer by layer. For other soils, however, important properties of a pedon are not observable in a smaller sample and detailed studies of the entire pedon are needed. For many soils, the information obtained from a small sample amply describes the pedon from which it is taken. Samples can be studied more rapidly than entire pedons consequently, a much larger number can be studied and for several more places. Knowledge of the internal properties of a soil is derived mainly from studies of such samples. For rapid investigations of thin soils, a small pit can be dug and a section of soil removed with a spade. During field operations, many soils are investigated by examining the soil material removed by a sampling tube or auger. The body may be larger than a pedon (e.g., a backhoe pit) or represent only a portion of a pedon (e.g., a sample from a hand auger).
Any standardized forms need to allow enough space for all possible information.Įach investigation of the internal properties of a soil is made on a soil body with certain dimensions. Furthermore, a standard format makes data entry into a computer database more efficient. The reader can find information more rapidly, and the writer is less likely to omit important features. Observations must not be limited by preconceived ideas about what is important.Īlthough the format of the description and the order in which individual properties are described are less important than the content of the description, a standard format has distinct advantages. Good judgment is needed to decide what properties merit detailed attention for any given pedon (sampling unit).
For some soils, other properties need to be described. This chapter does not discuss every possible soil property. Examples are the length of time that cracks remain open, the patterns of soil temperature and moisture, and the variations in size, shape, and hardness of clods in the surface layer of tilled soils. Many properties must be observed over time and summarized if one is to fully understand the soil being described and its response to short-term environmental changes. Some soil properties change through time. For some soils, standard terms are not adequate and must be supplemented by a narrative. It contains standard technical terms and their definitions for most soil properties and features and provides information for describing the necessary related facts. This chapter provides standards and guidelines for describing the soil. Examination and Description of Soil ProfilesĪ description of the soils is essential in any soil survey.
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