ISHS Acta Horticulturae 278: Symposium on Scheduling of Irrigation for Vegetable Crops under Field Condition
SOIL WATER CONTENT AND SALINITY ASSESSMENT FOR IRRIGATION SCHEDULING USING TIME-DOMAIN REFLECTOMETRY: PRINCIPLES AND APPLICATIONS |
| Authors: | F.N. Dalton, J.A. Poss |
| Abstract:
Irrigation scheduling for optimum yield attempts to minimize matric and osmotic stress over critical growth stages of a crop by determining when, how much, and at what rate to irrigate. These questions are answered by a variety of soil, plant and atmospheric measurements. While the application rate of irrigation water is primarily limited by the unsaturated hydraulic conductivity of the soil, the question of when and how much is often determined by soil water content measurements and, where necessary, soil salinity measurements. Time-domain reflectometry (TDR) is a new technique which is capable of simultaneously monitoring both soil water content and soil water salinity over identical sampling volumes using a single probe. The principles of TDR measurements are discussed and the use of commercially available TDR equipment as a moisture and conductivity gauge are explained in detail. Constraints on the separation, diameters, and lengths of TDR probes are given as a function of water content and pore water electrical conductivity. A TDR electrode insertion and cable tester quick disconnect system is described for column and field studies. TDR probes for permanent installation in the vadose zone are also described. | |
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