2018 ASHS Annual Conference

Growing media consists of mixtures of substrate components such as peat, pine bark, and coir. These components provide structure within the container to support plants and supply the essential water, air, and nutrients to promote plant growth. Factors which may affect air and water status within containers are the substrate components, container height, and irrigation practices. Understanding how these factors influence the retention and distribution of water within a container is essential in promoting water-use efficient practices. However, visualizing and quantifying the spatial distribution of water within a container has been difficult due to the opaque nature of substrate components. Recent advances in X-ray tomography and commercially-available analytical software have allowed researchers in plant and soil science to 3-dimensionally visualize and quantify plant-soil-water relations. Using a high-resolution X-ray microtomography scanner, the spatial distribution of water within various substrate components were volumetrically and spatially quantified after three irrigation practices were applied: over-head, drip, and sub-irrigation. As expected, water content increased from the top of the container to the bottom following irrigation. The layer commonly referred to as the “zone of saturation” in substrates was quantitatively characterized. For example, following an application of overhead irrigation, a pine bark substrate’s zone of saturation extended 2 cm above the base of the container and contained approximately 0.12 cm³/cm³ of air filled porosity. These results indicate that X-ray tomography is well equipped to assist researchers in understanding the dynamic interactions between substrates, containers, and irrigation practices.