Rudy Explains To Ally Why The Dirt Is Red In West Texas
Okay, so Ally and I were discussing the difference between the sandy soil of Andrews, Texas where she was raised, and the 'red dirt' here in Abilene. So, here's my simple explanation as to why our soil, clay, and or dirt here in Abilene and West Texas is red.
Why is Our West Texas Soil Red?
Red clay gets its color from an overabundance (and that is an understatement) of 'iron oxide' within it. Red clay (or "red-dirt" as we Texans so fondly call it) is created through the breakdown of rocks in its own underlayer of the soil. That breakdown comes from two sources one is done by mother nature with the pressure and soil shifting. The other is man-made by our poor agricultural choices.
That said, the most amazing part is that there's a lot of nutrients in our red clay/dirt. Besides the iron oxide, our soil also has magnesium, nitrogen, calcium, and potassium in it. While it might seem like our red soil cannot hold water, nothing could be further from the truth. The red clay has some incredible water-retaining properties and the red clay holds onto its nutrients like iron and nitrogen for a long period of time.
Soil is identified in the field by visual and mechanical tests. The criteria for these are grain size, color, density or consistency, and moisture content. For grain size, soil is either cohesive-clay, or cohesionless-silt, sand, or gravel. Most soil consists of a mixture of these grains and organic material.
1. Cohesive Soil
Cohesive soil (clay) is composed of extremely small mineral grains shaped like plates. Water is attracted between the plates by electrostatic forces to varying degrees based on the chemical composition of the clay. Clay exhibits a wide range of properties based on water content and chemical composition. When dry, clay is hard and rigid due to the close attraction between the grains. When clay is very wet, it exhibits an almost soupy consistency.
Clay occurs as both residual and sedimentary soil. Clay of a sedimentary origin is initially deposited in a soup-like state. In upland areas, water evaporation rapidly removes fresh clay deposits to produce fairly firm soil. In coastal areas, this usually does not occur due to high ground-water levels. In such an environment, the water is slowly squeezed from the clay by the weight of subsequently deposited overlying soil. The result is typically very soft surface clay that gradually increases in strength with depth.
2. Cohesionless Soil.
Cohesionless soil is composed of larger, more rounded particles than clay and is subdivided based on grain size. The most commonly encountered cohesionless soil is:
Silt (passes a No. 200 sieve)
Sand (passes a No. 4 sieve and is retained on a No. 200 sieve)
Gravel (passes a 3-in. sieve and is retained on a No. 4 sieve)
Because of our soil's unique composition, red dirt can be a blessing and a curse here's why: if you've ever been swimming in a tank or pond make sure you're not wearing anything white, or else it will be rust-red within minutes. The biggest downer about our red dirt is that due to the dry, then wet, then dry again weather our home's foundations take a beating and begin to crack.
To learn more about our West Texas red dirt and what can grow in it naturally check out the state's TxDOT website.