What Is Non-Percolating Clay?

Considerations

• Soil contains sand, silt and clay. Clay is the smallest type of particle found in soil, with each particle measuring less than .001 mm in diameter. The clay can pack together so tightly that water and air cannot penetrate it. In addition, the nature of clay prevents microorganisms from easily colonizing it and remediating the soil. Whether or not clay percolates depends upon the size of the particles and the composition of the minerals found within it.

Warning

• Most plants require well-drained soil. Non-percolating clay will cause plant roots to rot. With very fine clay, water may not penetrate at all or evaporate quickly, starving plants of water. Tight spacing between clay particles can prevent symbiotic microorganisms that plants need to survive from colonizing the soil. Septic systems, used predominately in rural areas for the breakdown of human waste and waste water, require percolating clay, or the system will clog.

Identification

• Since both non-percolating and percolating clay look identical to the human eye, you must test the soil to determine whether or not it percolates. Dig at least three holes in the ground where you plan to garden or install a septic system. These holes should measure at least 6 inches in diameter and 3 feet in depth. Fill the holes with water and allow them to drain completely in order to saturate the clay. Refill the holes with water and let them sit overnight. If water remains in the hole in the morning, the top layer of earth in your test area contains non-percolating clay.

Remedies

• You can remedy non-percolating clay for gardening purposes by spreading a few inches of topsoil on top of your planting area or by digging out the clay completely and replacing it with topsoil. Alternatively, build raised beds and fill them with topsoil. For septic systems, place the system underneath the layer of clay, select a new location or install a more costly drainage system that works in areas that will not percolate.