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Handbook of Soils for Landscape Architects$
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Robert F. Keefer

Print publication date: 1999

Print ISBN-13: 9780195121025

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195121025.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 18 September 2021

Physical Properties of Soils

Physical Properties of Soils

Chapter:
(p.27) 4 Physical Properties of Soils
Source:
Handbook of Soils for Landscape Architects
Author(s):

Robert F. Keefer

Publisher:
Oxford University Press
DOI:10.1093/oso/9780195121025.003.0006

Soil texture can be defined as the size and proportion of the soil particles—sand, silt, and clay—that are present in a soil. . . . Sand is the largest—from 0.05 to 2mm—and considered coarse texture; consists of angular spheres or cubes. Silt is intermediate—from 0.002 to 0.05mm—and considered medium texture; consists of properties between sand and clay. Clay is the smallest, being less than 0.002mm, and considered fine texture; appears as plate-like or flakes. . . . Any individual soil can be placed on the soil textural diagram when relative amounts of sand, silt, and clay are specified. As a general rule, the type of soil can be determined by feel when squeezed between the fingers. If the soil feels harsh and gritty it would be classified as a sandy soil. One that feels smooth and not sticky or plastic would be a silt soil, and one that is sticky or plastic would be a clay. Another way to distinguish between soils is their ability to form a ribbon. Soils that will not form a ribbon are sands. Those that form a fragile ribbon are loams; those that easily form a thick ribbon are clay loams; and those that easily form a long, thin, flexible ribbon are clays. . . . To be classified a sand, the soil must have more than 45% sand. To be classified a clay, the soil must have more than 20% clay. Loam is a mixture of sand, silt, and clay in about equal proportions. It is considered “ideal” for growing plants. . . . Weight of the soil solids is called “particle density.” For most common mineral soils (soils in which organic matter is usually less than 20%), particle density is about 2.65 g/cm3. Organic soils (where organic matter is greater than 20%) are usually about half as heavy, with particle density between 1.1 to 1.4 g/cm3. This measurement would be an important factor to consider if much material was to be transported for topsoiling.

Keywords:   bark, capillary movement, diffusion, field capacity, hardpans, infiltration, loam, macropores, organic soils, peat

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