REFINING THE DEFINITION OF FIELD-CAPACITY IN THE LITERATURE

The normalized water content calculated with the simple algebraic equa tion Theta(fc) = (q(fc)/K-s)(1/n), where q(fc) = 0.05 mm/day and K-s = hydraulic conductivity, can be used to estimate field capacity. The w ater content calculated with this relationship is close to the water c ontent at 1/3 bar matric potential for all soils. It is suggested that the concept of ''field capacity'' be refined by relating it to the mo bility of soil moisture (drainage flux). Field capacity should not be characterized solely by a particular drainage time, because the time t o reach field capacity depends on soil properties, but also on the ini tial water content and water depth in the soil.