Available Water Supply

Definition - What does Available Water Supply mean?

Available water supply is a term used in horticulture that refers to the amount of water that is stored in soil and available for plants. In other words, available water supply refers to the amount of water that is present and readily available for plant uptake. It does not include the small amounts of water that is bound tightly to soil particles.

Available water supply in soil is an indicator of soil quality. It can be used to calculate water budgets and predict droughts.

Available water supply is also referred to as available water capacity (AWC).

MaximumYield explains Available Water Supply

Available water supply can be calculated by mathematical equations and by using soil bulk and water content as variables. Additionally, in some areas like those with constant rainfall, the calculation of available water supply may be unnecessary. However, in areas that suffer from drought, knowing the available water supply can be crucial to crop success.

The amount of water retained in soil greatly depends on the make-up of the soil. For example, porous soils like loam can retain water; however, soils that are heavily made up of clay retain much less water. Water retention in soil is important because the water in the soil that can be retained helps prevent periods of water deficiency in plants. When not enough water is made available to plants, they can suffer from reduced growth, wilting, or death.

The concept of available water supply was first put forward by Frank Veihmeyer and Arthur Hendrickson, who assumed that the water readily available to plants is the difference between water content at field capacity and a plant's permanent wilting point. However, there are many variables at play that can affect the available water supply, such as the properties and requirements of the plants, as well as the soil and meteorological conditions.

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