How substrate structure influences air porosity
Air porosity is the percentage of air contained in a fixed volume of substrate after the substrate is saturated with water and the free water has drained. The higher the air porosity, the more oxygen the roots can acquire.
It is important to mention that some substrate components, like perlite, have closed pores. Therefore, even when the substrate is completely saturated, there are trapped air pockets within the component that cannot be used by the roots.
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