The Soil Triangle

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