A Technical Report from The Bartlett Tree Research Laboratories
The amount of water in the soil in large part determines how well trees and shrubs will establish and grow. Lack of water is one of the leading causes of failure of new plantings. Mature trees with root damage from construction injury, root rot or other factors also may die during drought periods due to their inability to take up adequate amounts of water.
Judging soil moisture level is difficult and often inaccurate without the aid of a soil moisture-measuring instrument. While there are different devices available, the most practical is the tensiometer (Figure 1). When properly installed in the soil, water moves in or out of the tensiometer tube through the ceramic tip to reach equilibrium with the soil. As the fluid moves out, a vacuum is created inside the tube and it is measured on the gauge. The higher the vacuum reading, the dryer the soil. When the soil is saturated, there is no suction because water moves back into the tube, so the gauge will register zero.