Clay is a thick, sticky soil that is difficult to till and hard for roots to penetrate. Clay soils compact easily, impairing oxygen circulation and water drainage. Soils high in clay content can have drainage issues that create problems for gardens and landscaping.
Characteristics of Clay Soil
Clay particles are so fine that water cannot easily drain through. According to the United States Geological Survey, the particles in clay are less than 2 micrometers (25,400 micrometers equals 1 inch), making clay very dense and compact. Wet clay absorbs water quickly and can swell to twice its size. When dry, clay contracts and becomes hard like concrete.
Solutions for Gardens
According to Colorado State University Extension, soils containing more than 20 per cent clay easily become waterlogged leading to root rot. Adding organic material such as compost, manure or humus loosens the soil and improves drainage. Another solution is to create raised planting beds by mounding the dirt.
Hard, compacted clay causes water to puddle or run off, creating drainage problems in yards and landscaping. Adding a shallow, sloped trench filled with gravel or rock to low-lying areas can increase drainage. For larger areas, install underground drains packed with gravel to improve water flow.