The pour-through procedure for monitoring container substrate chemical properties: a review

Authors: Altland, James

Submitted to: Horticulturae
Publication Type: Review Article
Publication Acceptance Date: 11/25/2021
Publication Date: 12/2/2021
Citation: Altland, J.E. 2021. The pour-through procedure for monitoring container substrate chemical properties: a review. Horticulturae. 7(12).Article 536. https://doi.org/10.3390/horticulturae7120536.
DOI: https://doi.org/10.3390/horticulturae7120536

Interpretive Summary: The pour-through procedure is a simple, robust, and scalable procedure that can be utilized by practitioners and researchers to provide accurate measures of pore water pH, a good approximation of EC and macronutrient concentrations, but limited resolution for monitoring micronutrient concentrations. Based on research published thus far, the procedure can be effectively applied to containers of almost any size and filled with any substrate. The procedure should be applied to containers that have been saturated and allowed to come to equilibrium for approximately 60 min. A displacement solution of tap water should be applied slowly, distributed evenly across the substrate surface avoiding container walls where channeling may occur, and in a manner that avoids mixing and contamination with the leached substrate solution. As with many analytical procedures, when done consistently over time with attention to details, the results provide meaningful data from which action (changes to a fertilizer program, for example) or inferences (in research) can be made.

Technical Abstract: The pour-through procedure is a non-destructive 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.