"By routinely measuring the electrical conductivity (EC) and pH of growing media and irrigation water for container-grown nursery crops, growers can monitor nutrient availability and scout for problems. This does not have to be time-consuming, complicated, or difficult. Learn how to use the pour-through extraction procedure as part of your nursery’s quality control program". NC Cooperative Extension has a new "Pour Through" publication outlining this process. Print it off and read it at: THE POUR-THROUGH EXTRACTION PROCEDURE.
For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.