12 - Inorganic and Synthetic Organic Components of Soilless Culture and Potting Mixes

Abstract

The components of soilless growing media and potting mixes used in horticulture are primarily selected based on their physical and chemical characteristics and, in particular, their superior ability to provide simultaneously sufficient levels of oxygen and water to the roots. There is a lot of variability in the origin and physical and chemical characteristics of the substrates used by the horticultural industry. Substrates are divided into inorganic and synthetic organic materials. The organic materials comprise synthetic substrates and natural organic matter. The inorganic substrates can be classified as natural unmodified materials and processed materials. This chapter provides the description of each substrate, which includes information on its production and origin, general information on its applications as a growth medium, or for other purpose. It sheds light on the physical characteristics, such as bulk density (BD), water retention, and hydraulic conductivity, as these properties are essential for proper irrigation management. Furthermore, it describes the chemical characteristics, i.e., composition, stability as affected by pH, cation exchange capacity (CEC), pH, and salinity, as these basic data are required for the proper management of fertilization and irrigation. In addition, it presents information on substrate sterilization, as disease control is a major factor in the successive use of substrates. Finally, it provides information on waste treatment since the potential for environmental contamination is becoming a central issue in intensive soilless cultivation.