Soil Properties

Texture of Soil

The physical texture of your soil can be important starting points for understanding what will grow best and what types of plants you will have a difficult time keeping happy. For example, if your soil is sandy and allows water to drain quickly, plants that require more water must be watered more often; and, plants that like well-drained soil may thrive more readily. The question is, what percent of clay, what percent of sand, and what percent of silt does your soil contain? These components determine soil texture. While a lab report can tell you what kind of soil texture you have by determining the particle size of elements (sand, silt, and clay are all defined by their size), you can also do a simple home test to determine your basic soil texture using the soil triangle. Take a jar and fill it 3/4ths full of soil from your growing medium. Add enough water to cover the soil a couple of inches. Then add a drop of soap, a drop about the size of a pea. Shake this bubbly mixture up and let it sit for several hours (days in some cases). You will see the soil particles settle out into layers. Next, using the following chart, determine where on the triangle your soil would be... This will give you a rough estimate of the texture of your soil. Visit an interactive soil triangle to help estimate your results.

Montana State University has a handout called Soil Testing and Fertilizer Guidelines written especially for Montana growing conditions.

Why is soil texture important?

The basic idea is that soil is made up of minerals and decomposed particles. We classify those into particles less than 2.0 mm in diameter and call them sand, silt, and clay. Sand particles are easily seen with the naked eye and feel "gritty" between our fingers. On the opposite end, clay particles are microscopic, and feel "slimy and sticky" between our fingers. In order for plants to take in nutrients properly, the soil needs to be composed of 25% air space, 25% water, 45% mineral, and 5% organic matter. All these components combined create the optimum soil. Understanding the balance can help us know how to amend soil or how soil might influence a plant's ability to take up nutrients. See more on Plants and Nutrients.

Understanding the Color of Soil

Want a more in-depth look at soil... sustainable management, soil organisms, the power of earthworms? Visit the ATTRA Sustainable Agriculture Program