Within the boundaries of Johnson County there are numerous natural soil types and mixtures of those types to consider when planning gardens or landscaping. One might think of soil types as either hard or easy digging, and those are definitely things to consider, but consider some other qualities, such as alkaline, acidic, stony, sandy, silty or clay for starters. Loam is soil material that is 7 - 27 percent clay, 28 – 50 percent silt, and less than 52 percent sand particles. Sand is mostly quartz and consists of 85 percent sand particles and less than 10 percent clay particles. Clay soil has a texture of 40 percent or more clay, less than 45 percent sand, and less than 40 percent silt. Sand particles size ranges from .05-2.0 millimeters and clay particles measure .002 millimeters or less in diameter. Silt particles vary between existing sand and clay particles in size although silt is usually used to describe soil with 80 percent or more silt and less than 12 percent clay particles. Layers of native soil are top soil, subsoil, and deep soil, each of which may differ in texture, pH, permeability and color from the abutting soil layers. Each can also differ in depth, stoniness, wetness, degree of erosion and slope with variable changes over time. Color of soils is usually influenced by the type of organic material and relief from which it was formed as is the soil acidity or alkalinity [pH]. Most annual and perennial plants prefer certain environment in which to live and prosper. Soil type and its characteristics are a big part of plant environment, particularly pH and permeability.
The above information is good information, but for shallow rooted plants, which includes most yard and garden plants, soil values mostly involve the top 12 inches or so of soil, which in many cases is trucked-in 'fill dirt'. For enhancing, tilling, testing, fertilizing, etc., this is the area to concentrate on. Trees and some shrubs require 'deeper' thought and action.
Soil particle size is important for water penetration [permeability] and drainage in flower and garden beds. The larger the particles the easier it is for the water to drain deep. This means that water permeates away from the upper soil faster in sand and gravel than in clay. Another drainage factor is the soil slope degree. Dig a test hole deeply in beds or lawns for a look at what is there.
Most plants do not like to stand in water or continuously wet soil. Being aware of these facts will help us better prepare plant beds before planting. Flower and vegetable plants are full of moisture and need water per each variety's desires, but constant watering without good drainage can be disastrous. Good drainage comes with proper soil or soil replacement. At the same time, remember that well drained areas require more frequent watering to maintain the plant's desirable moisture level. Trees or bedding plants planted over a hard rock or packed clay pan may drown because the water pools up at root level with slow evaporation or disbursement. It is easier and cheaper to adapt plants to your yard than to adapt your yard to your plants. This fact makes proper selection of plants a critical factor.
Some urban yards have poor topsoil trucked in from elsewhere to cover up landfill material possibly consisting of concrete chunks, bricks, plastics, paper, metal, wood, etc. which are not desirable soil enhancements. In these cases, additions of compost or other soil enhancements of the topsoil will be needed for plant success.
Soil testing is recommended in new yards or yards where poor results have occurred. Test kits are available from the County Extension Office and the lab fees are practical with results and recommendations within two weeks. These results will indicate what your yard soil contains in the way of nitrogen, phosphorous, potassium, and other minerals and whether acidic or alkaline with recommendations to improve the soil quality. Other tests are available for fungi, mold, etc.
Don’t miss Johnson County Master Gardener Jack Rowland, 11 a.m. – noon, Saturday Jan. 24, at the Cleburne Library for his free lecture “Your Vegetables are only as GOOD as your soil.” Learn from the expert and make sure you bring your vegetable gardening questions. Jack is also bringing soil sample kits from the County Extension so don’t forget to pick one up.
For more information contact the Johnson County Master Gardener Association www.jcmga.org or Pat Kriener 817-793-4625.