Soils is composed of five ingredients – minerals, organic matter, living organisms, water, and air. Soil minerals are divided into three size classes – clay, silt, and sand. Soil texture is determined by the percentage of each of these particles present in the soil. Clay is very fine and compacts tightly together, while sand is grainy and loosely combined. And the particle size of silt is between that of clay and sand. Of course, the soil texture of your yard could land anywhere along the soil spectrum. As you can imagine, your soil’s mineral makeup dramatically affects its drainage and nutrient power. A mixture of all three minerals is referred to as loam. Sandy loam contains about 25 percent clay, 50 percent sand, and 25 percent silt. Clay loam contains about 50 percent clay, 25 percent sand, and 25 percent silt. Testing your soil is the first step to understanding what type of seedbed you are working with. Once you know your soil type, you can modify it as needed to build the ideal growth environment for your turfgrass lawn. A moisture test is a quick way to determine the soil structure in your yard.
Moisture Test
- Collect a small amount of soil in the cupped palm of your hand
- Add a small amount of water (spit)
- Work the moisture into the soil with your finger
Clay Soil: If the soil works into a single large ball it is likely clay based soil. Clay soil compacts easily and requires more aeration to ensure that root growth isn’t stunted by lack of air, water and nutrients filtering through the soil. When watering clay soil you need to water stations for shorter times but multiple times in a day to prevent run off and add an air layer between waterings that pushes the water deeper into the soil bed.
Sandy Soil: If the soil resists balling up it is most likely sandy soil. Filtration rates on sandy soil are much higher so shorter more frequent watering times may be necessary until the grass is able develop a deep root system. Compaction isn’t as likely with sandy soil, but as air water and nutrients move through the root zone quicker it may take more water initially to develop a good root system. Sandy soils are best for lawns that have heavy traffic (sports fields, parks, etc.)
Sandy Loam Soil: If the soil works into several small balls it is likely clay based soil. Sandy loam is generally considered to be the preferred soil mixture for turfgrass lawns. It drains well but holds on to enough moisture to deliver the necessary nutrients for your lawn’s development. Most yards do not have perfectly blended sandy loam soil and can benefit from some amendment. Lawns grown on sandy loam soil don’t compact as quickly as clay based soils but can still benefit from an annual aeration.
In addition to the mineral components, your soil also contains nutrients derived from organic matter, living organisms, and fertilizer. Most garden centers carry soil test kits which will identify which nutrients your soil may need for proper turfgrass health. Even within the same subdivision, planting areas can be very different, so be sure to take the time to understand your yard environment. The best time to take a soil sample is before the turfgrass is planted. If possible, late winter is the optimal season to collect a soil sample because organic matter and living organisms are dormant making the soil stable. Samples should be taken from the turfgrass root zone, between two and ten inches below the surface. Soil tests are a tool to clue you in on what your turfgrass may lack. However, no test can replace your observations as you watch how your turfgrass responds to treatments you apply during the year. Record your observations and refer to them often when making fertilizer, herbicide, and pesticide decisions.
LEARN YOUR LAWN!