Abstract
The pour-through procedure is a nondestructive method commonly used by horticultural crop producers and research scientists to measure chemical properties and nutrient availability in container substrates. It is a method that uses water as a displacement solution to push the substrate solution out of the bottom of the container so it can be analyzed for pH, electrical conductivity, and nutrient concentrations. The method was first introduced in the early 1980s. Since then, research has been conducted to determine factors that affect the results of the pour-through including volume, nature and timing of application of the displacement solution, container size, and substrate stratification. It has also been validated against other common methods for determining container substrate pH, EC, and nutrient concentration, most notably the saturated media extraction procedure. Over the past 40 years, the method has been proven to be simple, robust, and consistent in providing crop producers and researchers valuable information on substrate chemical properties from which management decisions and experimental inferences can be made.
Highlights
United States Department of Agriculture, Application Technology Research Unit, Wooster, OH 44691, USA; Abstract: The pour-through procedure is a nondestructive method commonly used by horticultural crop producers and research scientists to measure chemical properties and nutrient availability in container substrates
After this equilibrium is reached, a small volume of water is poured over the container surface forcing a portion of the substrate solution to move out of the drainage holes at the container bottom
Subjecting container substrates to the saturated media extraction (SME) procedure requires additional deionized water be added to the substrate until all pore spaces are filled, resulting in 30% to 50% more water being added to the substrate solution based on the average air space of pine bark substrates [39]
Summary
The pour-through procedure, referred to as the Virginia Tech Extraction Method [1,2]. The procedure involves saturating container(s) to their water-holding capacity via normal irrigation, waiting 30 to 60 min for the substrate solution to come to equilibrium both in its physical movement through the container pore spaces, and in its chemical properties as the solution interacts with fertilizers and the substrate itself. After this equilibrium is reached, a small volume of water is poured over the container surface (displacement solution) forcing a portion of the substrate solution to move out of the drainage holes at the container bottom. The leached substrate solution is captured, measured immediately for pH or EC, or stored for later analysis of mineral nutrients [6]
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