Abstract:
A lack of in-situ instrumentation limits continuous monitoring of soil solution concentration to evaluate
environmental (contaminants) and agricultural management (plant nutrients) practices. We developed a prototype
soil solution monitoring technique, to measure long-term in-situ nitrate concentration, consisting of an in-situ
stainless-steel porous cup, with real time concentration measurements using a UV fiber-optic sensor and Ion
Selective Electrode (ISE). The measurement technique does not require soil solution extraction, but is based on insitu
soil solution equilibration by diffusion between the porous cup and the surrounding medium. The technique is
presented for nitrate solution with sandy soil using new designed of solution samplers. Analytical solutions are
presented to evaluate solute diffusion coefficients, as controlled by a variety of soil water contents. The principles of
operation are demonstrated for diffusion a saturated and unsaturated Oso Flaco Sand, illustrating the potential
application solution samplers in a soil environment.
