Integral energy as a measure of soil-water availability

The available water capacity is the most commonly used parameter to quantify the amount of water readily available to plants. However, it does not directly describe the energy requirements of the plant to remove a unit amount of water from the soil at various moisture contents within the available range. We present the integral energy concept as an attempt to quantify this. It is calculated from the integral of a soilʹs water-retention curve. We demonstrate the calculation for different types of soil. The integral energy provides useful information regarding the amount of energy, and hence the availability of water to plants. The value appears to be more correlated with basic soil physical properties, such as clay and sand content, compared with the conventional available water capacity.