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AE446: Smart Irrigation Controllers: Operation of Evapotranspiration-Based Controllers

Figure 4. Diagram of water content in the root zone including: saturation where all soil pore space is filled with water, field capacity is the water remaining in soil pores after gravitational drainage has ceased, permanent wilting point is only thin films of water remaining that is not available to plants. Available water (AW) is the total amount of water held by the soil for plant use, and readily available water (RAW) is the amount of water available for plant use before stress.

Credit: Mary L. Shedd