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Title: SOIL PENETROMETERS AND PENETRABILITY

Author
item LOWERY, BIRL - UNIV OF WISCONSIN-MADISON
item Morrison Jr, John

Submitted to: Soil Science Society of America Special Publication Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 10/15/2002
Publication Date: 10/15/2002
Citation: LOWERY, B., MORRISON JR, J.E. SOIL PENETROMETERS AND PENETRABILITY. DANE, J.H., TOP, G.C., EDITORS. SOIL SCIENCE SOCIETY OF AMERICA BOOK SERIES: 5, MADISON, WI. METHODS OF SOIL ANALYSIS, PART 4 PHYSCIAL METHODS; CHAPTER 2.8. 2002. p. 363-388.

Interpretive Summary: Agricultural soils are the "factories" for agricultural crop production. It is valuable to examine and classify the soil at any location to establish its properties or characteristics for a proposed agricultural production scheme. To do such examinations we need to determine not only the surface conditions, but also the characteristics of the soil profile. "Soil penetrometers" are measuring instruments used for such soil examinations. Various types of penetrometer instruments are being used to investigate, describe, and catalog localized soil characteristics. Penetrometer use for evaluating soil properties has allowed researchers to refine the techniques to allow for more precise and varied types of applications. In the past, cone-type penetrometers have been used extensively to characterize soil profiles with respect to compaction and root growth. We anticipate greater use in future with respect to assessing soil variability, because the procedures are relatively rapid and non-invasive. Current and new developments will make this technology a more reliable means for characterizing soils for applications such as site-specific farming. We have also presented literature review information on the use of penetrometers for in situ determination of properties in addition to penetration resistance, such as contaminants in soil and soil water content.

Technical Abstract: Force required to drive or push a device into the soil is a measure of the soil penetrability. Soil penetrability is measured with a device called a penetrometer. A penetrometer consists of a rod/shaft with a flat end, an enlarged cone tip, or an enlarged flat plate end. Penetrometers with a flat-end shaft are typically used to test soil surface strength or near-surface soil conditions. An enlarged cone tip is the most commonly used penetrometer for agricultural applications to investigate the soil profile. Flat plate penetrometers are used to test the strength of exposed soil layers. Penetrometer data is typically reported as the resistance to soil penetration in terms of penetration force per unit area, or pressure, under the effective area. This resistance pressure may be reported as "Cone Index" (CI), in the pressure units of pascals (Pa), kilo pascals (kPa), or mega pascals (MPa); (1 Pa = 1 N/m**2). The objectives of a particular investigation and to some extent soil conditions, including maximum depth to be investigated, will influence the penetration method to be used. Penetrometers and penetration methods can be simple or highly mechanized and very sophisticated. In this chapter, several current methods are presented; they include both laboratory and field apparatus and procedures, ranging from the use of inexpensive devices to sophisticated digital-recording, power-driven penetrometers.