Vermiculite is mica heated to 1,400 degrees, expanding it into particles capable of holding much air, water and nutrients. The mineral itself contains potassium, magnesium and calcium available in slow release. It has an absorbent capacity for fertilizer and also buffering and oxygen exchange.
Perlite is a volcanic material heated to 1,800 degrees making it porous. The particles provide excellent drainage while trapping air and water on its' irregular surface. Perlite will hold 3-4 times it own weight in water. It is neutral in reaction and has no buffering action.
It is normally used in a 50/50 mix in hydroponics, sometimes adding coco peat for extra water holding ability. It can be mixed with soil to allow for better aeration of the medium. They are sold in .4 cubic foot bags and 6 cubic foot bales.
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