Soil Moisture Hysteresis
Soil moisture hysteresis refers to the difference in the water content of a soil at a given matric potential, depending on whether the soil is wetting or drying. It can be expressed as the difference in gravimetric water content or volumetric water content between the wetting and drying curves at the same matric potential.
What is the best measure of moisture?
The best measure of moisture depends on the specific application and the soil properties being considered. Some common measures of moisture include:
- Gravimetric water content is the ratio of the mass of water in a soil sample to the mass of the dry soil.
- Volumetric water content is the ratio of the volume of water in a soil sample to the total volume of the soil sample.
- Matric potential is the difference in water pressure between the soil water and the surrounding atmosphere.
For many applications, gravimetric water content is the most useful measure of moisture because it is relatively easy to measure and can be directly related to the amount of water available to plants.
Factors affecting soil moisture hysteresis
Several factors can affect soil moisture hysteresis, including:
- Soil texture: Soils with a higher percentage of clay particles tend to exhibit more hysteresis than soils with a higher percentage of sand particles.
- Organic matter content: Soils with a higher organic matter content tend to exhibit less hysteresis than soils with a lower organic matter content.
- Soil structure: Soils with a well-developed structure tend to exhibit less hysteresis than soils with a poorly developed structure.
- Wetting and drying history: The wetting and drying history of a soil can also affect hysteresis.