## Physical Properties

The physical properties can be determined at different resolutions.

Many of the physical properties can be judged by the way the soil looks, feels, and sounds. These are frequently considered first. From these properties many other properties can be determined or inferred.

### The Breadth of Physical Properties

The size of mineral particles that comprise soils are considered first in the Size Separates section of this reader.

While this seems arbitrary, the divisions are practical in that they are grouped into discernible divisions that can be delineated without advanced instrumentation–on site with tactical and visual learned skills–or with more refined instrumentation and techniques that are employed because the delineation serves a purpose in delineation of the soil for its use or service.

Cataloging size separates into groupings allows classifying into a Textural Class. Textural Class is sometimes shortened to simply Texture', but this shorthand, belittles that it is inherently a classification. Note that there exist alternative classification system for the size separates, but the most widely employed is the United State Department of Agricultures system. Presented in this Reader is the twelve class classification, but a five class and a three class system exist and are employed in soil interpretative information.

The textural class offers some insight into how the size separates become arranged, assembled, or aggregated, into secondary shapes that together are defined as structure and presented in this reader as structure or Particle Arrangement.

The relative proportions of the size separates their grouping into textural classes and the structure all impact the relationship between the solids and pore space between them in the soil fabric. This reader delineates the Density and the Porosity to help learners get at the interplay between the two that leads to a more fruitful understanding of soil water availability, soil temperature, and soil aeration offered in this Readers Climate section of the Reader.

Together with learning offered in the Readers Chemical section, the soils color can be very telling about soil water availability, soil temperature, and soil aeration, and the content of Soil Organic Matter, or SOM'. (The SOM is nested in this Readers Biology section.)

Soil Textural Class, with its implications for Density and the Porosity together with the content of Soil Organic Matter interact with, and impact, soil water. Together these help to understand the introduction to Soil Engineering properties.

On of the most compelling impacts of human management is the acceleration of Soil Erosion.