If you’re interested in growing plants of any kind, it’s important that you understand how important your soil is. From a conservation standpoint, soil helps filter rainwater, preventing contaminants from entering the aquifer, and regulates runoff into the ground, which prevents flooding. Soil is an important sequester of carbon, provides a home to fungi, bacteria, insects, and other living things, and has even been used as a construction material. Soil provides a firm foundation for plant roots to grow into and provides an avenue for plants to receive the nutrients they need in order to grow. For the next few weeks, we are going to dig more into why soil is so important for agriculture and growing things.
Soil texture is an important part of water and nutrient management for growing plants or crops because it influences retention. When we discuss soil, we are talking about all of the particles that are less than 2mm in size. Anything larger than this are considered coarse fractions, which include stone and gravel. The “fine earth fraction” less than 2mm in size includes sand, silt, and clay particles. Sand is the largest, with a size from 0.05mm to 2mm in diameter, silt ranges from 0.002mm to 0.05mm, and clay is the smallest, with particles less than 0.002mm. Sand is angular and gritty, creating larger spaces between particles, and allows a lot of water and nutrients to run through it. Clay has very small spaces between particles and a sticky, soft feeling to it. Clay tends to prevent water and nutrient runoff. Silt is somewhere in the middle, with a texture almost like flour. Soil texture results from the relative proportion of sand, silt, and clay particles found in a soil. Each particle contributes specific characteristics in regards to water infiltration, permeability, aeration or oxygen availability, and drainage.
The USDA recognizes 12 soil texture classes: sand, loamy sand, sandy loam, sandy clay loam, loam, silt loam, silt, silty clay loam, clay, clay loam, sandy clay and silty clay. These can be arranged in something called a “textural triangle” that indicates which of the 3 particle sizes they’re composed of. When we’re trying to garden or grow plants, we’re looking for soil with a perfect blend of particle size, that holds just enough water, nutrients, and air for our plants to thrive. Typically, this is a loam type of soil.
At websoilsurvey.nrcs.usda.gov/app, you can find physical maps of Lincoln County that illustrate the different types of soil present in different regions. For example, my property is primarily a clay and silt loam. These soils range from floury to sticky when most and easily form or compact into a ball that tolerates being handled. They hold both water and nutrients effectively (the clay holding more than the silt), which means they are pretty tolerant of drought. However, because they hold water, they can have trouble draining effectively during periods of heavy rainfall. An alternative to using the soil map is just to use the “feel” of it. When dry, does the soil feel soft or gritty? If you moisten the soil, can you form it into a tight ball with your fist? Sandy soils will not make a good ball, but clay soils will. If you squeeze some soil between your fingers, does it produce a “ribbon” of soil that holds it’s shape? That’s probably clay. If there’s no ribbon, or the ribbon is less than 1 inch long, It’s probably silt or a type of loam.
Figuring out what type of soil you have on your property is important for planning management of fertility, pH, irrigation, and drainage. If you need help figuring out your soil texture, please let us know at uge3181@uga.edu or 706-359-3233.
