Soil Physical Properties

Since we just had a spring break and I probably forgot all the information that I learned, I thought it would be smart to go ahead and regurgitate the information that we have learned. I really want to talk about soil physical properties and water science. I fell as if writing all of this down will give me a better understanding of the material while preparing myself for the test that is going to be tomorrow. Sorry if it is boring.

Soil Color is one of the first things we learned in this section, and we learned that soil color is easily influenced by parent material and vegetation. Soil texture can be divided into three separates. Sand (2.0-0.05 mm), silt (0.05-.002 mm), and clay (less than .002mm). Soil texture is the single most important physical properties of soil. Knowing the texture will provide info about: water-flow potential, water-holding capacity, fertility potential, fate of organic and inorganic contaminates, and suitability for many urban uses. In sand the porosity is in big spaces so that allows water to flow very easily through the sand but in clay, the water moves in different directions due to the small pore spaces and the adhesion to the clay particles. Clay also has the highest water-holding capacity due to its high surface area it has the ability attach to the molecules. Clay also can attach itself to contaminates that could make its way to a groundwater supply. There are two different ways that you can find out the soil’s textures, one is the texture-by-feel which is a method that one might use in the field and the other method is using the principles of dispersion and sedimentation. You can prepare a soil suspension and convert hydrometer measurements in a lab to find out the particle size.

As particle size goes up surface area goes down, thus they are inversely related. Soil compressibility is the soils tendency to consolidate or decrease in volume. Bulk density is the measure of compaction in a specific volume. Porosity is how much open air space there is per volume. Bulk density and porosity are also inversely related. Bulk density = weight of soil/ volume. Soil’s strength is the soil’s ability to resist deformation, function of cohesive and frictional forces between soil particles. The bearing capacity is the ability to soil to withstand a load. This is based on the soil’s texture. soil stability, and soil compaction.

There are 6 main soil structures: Granular, Platy, Angular, Subangular, Prismatic, and Columnar. Granular is usually found in the A horizon and is 1-10 mm. Platy is usually found in the E horizon but can be found in the B as well. Play is also 1-10 mm. Subangular and Angular are both considered blocky structures and are found in the B horizon (5-50 mm). The last two are Columnar and Prismatic and the only difference between the two is that Columnar has a rounded top. They are both found in the B horizon and are 10-100 mm. Soil granules can clump or bind together and then this is what we call soil aggregates. Roots, hyphae, spores, silt, clay, sand, iron oxides, and debris can all be found in soil aggregates.

Water molecules are very important to soil science. The hydrogen in H2O has one electron and gets one from oxygen. It has a polar bond which helps it dissolve other compounds and be reactive in the environment. Because it is polar it can also remain liquid for a wide temperature range. The last thing I wanted to talk about is adhesion, cohesion, and gravitational. Adhesion-the attraction of water to soil particles. Cohesion-attraction of water to itself. Gravitational-water that moves through water by soil.

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