ABSTRACT
Introduction For rooting medium hydroponic culture systems, plants are rooted in an inorganic substrate with the nutrient solution applied by either periodically flooding the rooting media or by the use of a drip irrigation system. Some of the physical and chemical properties of commonly used inorganic substrates are given in Table 5.1. From this list, it can be seen that growers have a wide range of rooting media to choose from. In the past, course sand and pea gravel (materials that may have to be acid washed to remove unwanted substances and then, when once used, were usually discarded) were the media of choice. In addition, both substances have high volume weight and therefore require the use of sturdy rooting vessels. In addition, the flood-and-drain hydroponic growing system requires a rooting material that will not be moved within the rooting vessel when flooded with nutrient solution.
