3 - Physical Characteristics of Soilless Media

Abstract

All media are composed of three phases: solid, aqueous, and gaseous. This chapter discusses the physical characteristics of these three phases separately and in combination. The physical properties of soilless media comprise bulk density, particle size distribution, porosity, and pore distribution. Following this, the study describeswater content and water potential in soilless media as another physical characteristic. Water content or wetness of a porous medium is the volume or mass of water occupying space within the pores. Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension. Subsequently, the study explains water movement in soilless media. Water is transported through the growing medium into the roots and plant xylem towards the plant canopy where it eventually transpires into the atmosphere. The continuous uptake of water is essential for the growth and survival of plants. Finally, it provides an understanding of solute transport and gas transport in soilless media. The movement and fate of solutes in soil are affected by a large number of physical, chemical, and microbiological processes, and the understanding of gas transport in growing media is important for the evaluation of soil aeration or movement of oxygen from the atmosphere to the medium.