Hysteresis

• The phenomenon which exhibits the difference in the relationship between the soil water content and soil water potential when drying and rewetting of the same soil is called hysteresis. The hysteresis phenomenon is illustrated in figure below.
• The hysteresis is caused by number of factors including non-uniformity of soil pores, entrapment of air that prevents the water penetration.
• Some of the macropores in soil are surrounded by micropores creating bottleneck effect.
• Also, the drying and rewetting of the soil causes swelling and shrinking of clays that destroys soil structure affecting soil water relationships.