Water management requires an understanding of water, irrigation, soil, and how they all relate to one another as well as the understanding of important Water Management Terms. Soil provides support and the nutrient reservoir necessary for plant growth. Water is essential for plant life processes. Effective management of these resources for crops and landscapes requires growers and landscapers to understand relationships between soil, water, and plants. This relationship is significant to irrigation users that desire to use best management practices such as irrigation scheduling.
Understanding the 12 water management terms below will increase your understanding of the plant water and soil relationship and make you a better water manager. If you want extra credit, you can watch the video below from the Jain Irrigation Training Series. It features Dr. Franklin Gaudi from the Irrigation Training and Research Center at California Polytechnic State University, San Luis Obispo.
Soil Texture
The most important water management term is soil texture. Sand, silt, and clay are the three primary particles found in soil. Soil texture indicates the amount of each in the soil. For example, loam soil is 20% clay, 40% sand, and 40% silt.
Here is a link to Web Soil Survey that shows you the texture of your soil once you put in your address. https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
Soil Structure
This is how the texture of the soil is put together. The smaller parts of the soil assemble, creating a larger particle. How these larger sections of soil are assembled refers to the soil structure.
Source: USDA / NRCS
Soil saturation
This is the point at which there is no air in the soil. All the spaces between the soil particles are filled with water.
Oven dry
Another interesting water management term is Oven Dry, this is when there is zero moisture in the soil.
Air dry
When water is present in the soil but not usable by plants.
Field capacity
This is the amount of water in the soil held by the soil—the remaining water left in the soil after it has been fully saturated and allowed to drain.
Permanent wilting point
When a plant reaches permanent wilting point, it can no longer recover from wilting.
Available water holding capacity (AWHC)
This is the difference between permanent wilting point and field capacity. 1.5 inches per sq ft for sandy loam soil. Here are a few other examples of AWHC for specific soils. This is of particular importance when determining how frequently to water. If you need an inch of water per week to replenish ET and have coarse sand, you will have to water more than once per week.
| Soil Texture | Inches Available Water/Ft of Soil |
| Coarse Sand | 0.5 |
| Fine Sand | 0.75 |
| Loamy Sand | 1 |
| Sandy Loam | 1.25 |
| Loam | 1.50 – 2.0 |
| Clay Loam, Silt Loam | 1.75 – 2.50 |
| Clay | 2.0 – 2.40 |
Soil moisture depletion
The amount of water needed to return the soil to field capacity, an often overlooked water management term, the soil moisture depletion can be calculated with onboard sensors for an accurate result as well as just plain-math calculation if we had the ET values for a particular location. Jain Logic does provide this feature using both sensors and satellite imagery.
Soil moisture content
The amount of water present in the soil, just like soil moisture depletion this term can also be calculated with soil moisture sensors in the field using Jain Logic’s soil moisture monitoring feature, this helps the grower understand how much water is actually required in his or her field.
Dr. Gaudi was a guest on the Jain Irrigation Training Series and discussed all these terms in great detail, and you can watch the training for free below. Please let us know what you think in the comments, and if you like the train, please subscribe to our youtube channel.