AGR 2320 Lecture Notes - Lecture 16: Capillary Action, Relative Permittivity, Semipermeable Membrane
17 Oct 2016
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Agr 2320 lecture 16 water in soil. Clay soil eventually has the highest capillary action, but it takes a much longer time than sand. Direct (go to field and take sample: sample & oven dry to determine how much mass in volume water there is. In situ (measure with a meter in the field, sample is not needed: neutron probe. Based on water and hydrogen bouncing back: tdr (time domain reflectometry) Tdr units generate em waves in radio frequency range. Velocity of electrical signal is reduced by materials with a high dielectric constant b/c vibration and alignment of molecules removes energy from signal. Water has a greater dialectric constant than soil or air. The greater the water content, the greater time required for electrical pulse to return: gpr (ground penetrating radar) Benefits: can drag it across the ground and you get a measurement. Limitations: doesn"t penetrate that far into the ground, especially with clay based soils.
