An overview of new and revised methodologies and technologies in substrate analysis and characterization

Abstract

Substrate research, analysis, development, and characterization remain critically important in the 21 st century as horticulture and plant production continues to evolve and meet new challenges in today's ever-changing world. Three areas of substrate research in the Horticultural Substrates Lab at North Carolina State University have seen recent new methodologies and technologies introduced: root development and assessment, enhanced physical properties, and engineering and substrate construction. The mini-Horhizotron is a three-chambered device with clear sides (and detachable shade panels) that can be utilized to measure (manually or digitally) root growth and development, root branching and architecture, root hairs, root disease and overall health. The rhizometer is a clear cylinder apparatus that can be utilized to measure the influence of plant roots (undisturbed) on substrate physical properties over time. The clear cylinder design also offers the ability to observe and measure multiple root parameters over time without disturbance. Techniques to determine the wettability of substrates include the hydration efficiency and water capture method and contact angle measurements. The use of dewpoint potentiametry to directly measure substrate water potentials is providing new data on substrate unavailable water and permanent wilt ranges for horticultural crops. Advancements in organic matter processing and engineering (specifically bark and wood) have led to a better understanding of how various factors including moisture content, species, particle size, and machine type influence the consistency and reproducibility of these substrate components. New substrate fractioning and reconstruction techniques have been recently identified and studied to decrease weight/density and allow manufacturers to better be able to "design and build" substrates for specific purposes. The study of substrate particles is evolving to be able to measure surface area (external and internal) and identify specific particle shapes. Specific surface area and particle shape analysis can contribute to a greater understanding of how those parameters influence air and water relations, nitrogen drawdown potential, and shrinkage/decomposition in substrates. Advances in thermal imaging and near-infrared spectroscopy are also explored. These recent methods and techniques have the potential to further substrate science in the future and aid in our ability to design and construct substrates for maximum efficiency and productivity.