Soil water balance and transport processes Review of theory and field applications

The theory of soil water balance and transport processes is reviewed. The main subjects are: measurement of crop water consumption; principles of soil water behaviour; measuring techniques of soil water content and potential, such as dielectric methods, the gravimetric method, neutron scattering techniques, and the use of piezometers and tensiometers; theory, principles and applications of time-domain reflectometry; water transport at the soil-root interface; and the soil water balance approach to crop water requirement studies. Applications to soil water management in agriculture include: determination of the direction and quantity of soil water flow; determination of the soil water characteristic curve or retentivity curve; irrigation scheduling; measurement of unsaturated hydraulic conductivity; and measuring crop evapotranspiration in the field.