International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



(6487) Total potential (of soil water)
The amount of work that must be done per unit quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water from a pool of pure water,at a specified elevation and at atmospheric pressure, to the soil water (at the point under consideration). The total potential (of soil water) consists of the following : 1 - Osmotic potential : The amount of work that must be done per unit quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water from a pool of pure water, at a specified elevation and at atmospheric pressure, to a pool of water identical in composition to the soil water (at the point of consideration), but in all other respects being identical to the reference pool. 2 - Gravitational potential : The amount of work that must be done per unit quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water, identical in composition to the soil water, from a pool at a specified elevation and at atmospheric pressure, to a similar pool at the elevation of the point under consideration. 3 – Capillary (matric) potential : The amount of work that must be done per unit quantity of pure water in order to transport reversibly an isothermally and infinitesimal quantity of water, identical in composition to the soil water, from a pool at the elevation and the external gas pressure of the point under consideration, to the soil water. 4 - Gas pressure potential : This potential component is to be considered only when external gas pressure differs from atmospheric pressure as e.g., in a pressure membrane apparatus.

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