Plants need water to survive. But too much water can suffocate plants. Too little water, and plants will wilt and die.
If you’re planting a garden, then you’ll want soil that will hold moisture in approximately half of its porous space. The other half of the porous space should hold air.
Soil drainage means how much water moves through and across the soil, how fast it moves, and how far it moves.
Sloping ground, especially in desert or arid areas, is a significant factor in drainage.
But there are other factors that affect drainage: soil texture, structure and the physical condition of the topsoil and subsoil.
The color of your soil can often tell you something about its drainage capabilities. Clear and bright colors generally mean that the soil drains well. Gray-colored soils, mixed colors or drab-looking soils can mean the reverse.
Hollows, low areas and bottoms of slopes usually receive more water than others, because these areas not only get precipitation, but runoff from other areas. Often, water from low areas escapes by sideways movement through soil or by evaporation, if the soil in these areas is structurally poor.
Soil Depth
Soil must extend far enough down from the surface for plants to grow. Contrary to what many believe, soil does not go on forever. In many desert and arid areas, there are several inches (anywhere from one to 15 inches) of topsoil. At that point, caliche or hardpan begins. In many areas, bedrock or a layer of gravel are encountered. In others, sand or impenetrable mucky clay.
Here are some rough estimates of soil depths:
- Very Shallow. There is less than 10 inches of soil. This can inhibit the development of roots.
- Shallow. Soil is 10 – 20 inches deep.
- Moderately Deep. Soil is 20 – 36 inches deep.
- Deep. Soil extends 36-60 inches.
- Very Deep. Over 60 inches.
Deep soils are of course, more desirable than shallow. However, many desert plants have specially adapted to shallow soil conditions. If you have shallow soil, put these plants in transition or arid zones.
See also:
Caliche - Hard Desert Gardening
Does Your Soil Have Structure?
Color and Texture in Desert Soils
