How Does Saturated Soil Happen?

Water Holding Capacity

• Soil is composed of solid materials, gasses and liquids. When a soil is saturated, all of the spaces where air can be are filled with water. When a soil first becomes wet, its surface layer gets saturated. This saturation layer gradually moves deeper into the soil as more water comes in contact with the soil. After saturation, a soil moves through three levels of drying. "Field capacity" is the amount of water held in a soil after all of the free water has drained due to gravity. "Wilting point" is the amount of water left in the soil after plants have become strained from water scarcity. "Oven dry" is when all microscopic water has been removed from the soil.

Organic Matter

• The decayed structures and byproducts of plants and animals provide the material for organic matter in the soil, which increases its surface area and ability to absorb and hold water. Organic matter can hold many times its volume in water. The more organic matter in a soil, the longer it will remain saturated. Organic matter holds water in the soil against the pull of gravity.

Soil Texture

• The soil's texture is determined by the percentage of sand, silt and clay in it. A soil needs to have a well balanced texture, with roughly equal percentages of sand, silt and clay to hold onto water. A soil with only small clay particles will hold too much water and will remain saturated for long periods. A soil with mostly sand will not hold onto water long enough for most plants to absorb the water they need.

Soil Structure

• Soil is a mixture of three different-sized mineral particles. Sand particles are the largest, followed by silt and clay particles. When a soil has a lot of clay and silt, the three different sizes of particles adhere much more strongly. Plant roots secrete organic compounds that also serve to glue tiny soil particles together. A soil's structure is a measure of the aggregates of sand, silt and clay that have formed in it. A well developed soil structure will help a saturated soil to drain. A compacted soil has had its structure destroyed and will stay saturated longer.