PRS Technology

Basics

Plant Root Simulator (PRS®) probes are ion exchange resin membranes held in plastic supports that are easily inserted into soil to measure ion supply in situ with minimal disturbance. 

Anion probes (orange) have a positively-charged membrane to simultaneously attract and adsorb all negatively-charged anions, such as nitrate (NO3-), phosphate (H2PO4-, HPO42-), and sulphate (SO42-).

Cation probes (purple) have a negatively-charged membrane to simultaneously attract and adsorb all positively-charged cations, such as ammonium (NH4+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+).

Prior to use, ion exchange membranes are saturated with a counter-ion that is easily desorbed, allowing ready absorption of soil ions.  Anion probes are saturated with HCO3- and cation probes are saturated with Na+.

When buried, soil ions displace the counter-ions at a rate that depends on their activity and diffusion rate in soil solution.  The quantity of soil ions adsorbed during a burial period is a function of all soil properties (physical, chemical, and biological) controlling nutrient availability in soil.

PRS® probes are a convenient and economical means of quantifying both spatial and temporal variations in nutrient supply rates for all soil ions simultaneously, making them an essential tool in agronomic, forestry, and ecological research.

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