The Soil Triangle and Questions (Apologies for its lateness!)

We will cover this in class.  The following is a set of practice questions you can use to determine your ability to use the Soil Triangle.  This is not an assignment you need to turn in. 

Using the Soil Texture Triangle

Follow these steps to determine the name of your soil texture:

1. Place the edge of a ruler or other straight edge at the point along the base of the triangle that represents the percent of sand in your sample. Position the ruler on or parallel to the lines which slant toward the base of the triangle.

2. Place the edge of a second ruler at the point along the right side of the triangle that represents the percent of silt in your sample. Position the ruler on or parallel to the lines which slant toward the base of the triangle.

3. Place the point of a pencil or pen at the point where the two lines meet. Place the top edge of one of the rulers on the mark, and hold the ruler parallel to the horizontal lines. The number on the left should be the percent of clay in the sample.

The descriptive name of the soil sample is written in the shaded area where the mark is located. If the mark should fall directly on a line between two descriptions, record both names.

Sand will feel "gritty", while silt will feel like powder or flour. Clay will feel "sticky" and hard to squeeze, and will probably stick to your hand. Looking at the textural triangle, try to estimate how much sand, silt, or clay is in the sample. Find the name of the texture that this soil corresponds to.

Practice Exercises

Use the following numbers to determine the soil texture name using the textural triangle. When a number is missing, fill in the blanks (the sum of % sand, silt and clay should always add up to 100%) - the last line has been left blank for you to fill in the numbers you assign to your own soil sample.

% SAND	%SILT	%CLAY	TEXTURE NAME
75	10	15	sandy loam
10	83	7
42		37
	52	21
	35	50
30	55
37		21
5	70
55		40
	45	10

A Soils Bibliography

Out of the Earth: Civilization and the Life of the Soil; ©1992 University of California Press , Hillel, Daniel. Hillel has written one of the most beautiful books on soil that has ever been published. This book introduces a little of soil science to the reader, but more than that, it fosters a love of the soil and an understanding about the magnitude and gravity of misuse and degradation; civilizations have paid little heed to the soil underfoot and it has cost them dearly. A delightful read!

Soils and Men, Yearbook of Agriculture 1938, © 1938, United States Department of Agriculture, The Committee on Soils. A government publication, no sane person will read from beginning to end! It is referenced here because it clearly shows the US government knew about the soil food web as early as 1938 and chose to ignore that information in favor of more commerce in chemical based fertilizers. We are at a point where ignoring the soil food web is too costly to continue.

Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition, © 2010 Timber Press, Lowenfels, Jeff and Lewis, Wayne. This is the second edition of the book that blew my eyes open on the biology of the soil and how we cannot ignore that biology plays at least as big a part of soil fertility as chemistry. We ignore biology to our own detriment and destroy our soils.

The Rodale Book of Composting, ©1992 Rodale Press, Martin, Deborah and Gershuny, Grace Editors. This is the only book to read on composting. Everything else is compostable.

The Soul of Soil; A Guide to Ecological Soil Management, 2nd Edition, ©1986; Gaia Services, Gershuny, Grace. This fabulous and passionate book is injured by being targeted to farmers (only) and therefore all recommendations are written in “pound per acre,” when we need ounces per 100 square feet. When I used this book, I wrote up a formula in Excel to convert all these into a usable figure.

The Worst Hard Time, The Untold Story of Those Who Survived The Great American Dustbowl © 2006; Mariner Reprint Edition, Egan, Timothy. Not strictly a soils book, but a real eye opener that shows how we are repeating many of the same mistakes today as what lead to the disaster we call the Dustbowl. This book is gripping reading and is not fiction. It really happened and it happened on a scale unprecedented in modern times. We can do it again if we fail to heed these words. A VERY good read on soils and man's relationship to them.