The World Known Growing Media
Peat and Peat-Like Materials
Peat moss is formed by the accumulation of plant materials in poorly drained areas. The type of plant material and degree of decomposition largely determine its value for use in a growing medium.
Wood Residues
Wood residues constitute a significant source of soilless growing media. These materials are generally by products of the lumber industry and are readily available in large quantities. Nitrogen depletion by soil microorganisms, during the decomposition process, is one of the primary problems associated with these materials.
Bagasse
Bagasse is a waste by product of the sugar industry. It may be shredded and /or composted to produce a material which can increase the aeration and drainage properties of container media. Because of its high sugar content, rapid microbial activity results after the incorporation of bagasse into a media.
Rice Hulls
Rice hulls are a by product of the milling industry. Although they are extremely light in weight, rice hulls are very effective at improving drainage. The particle size and resistance to decomposition of rice hulls and sawdust are very similar.
Perlite
Perlite is a siliceous mineral of volcanic origin. The grades used in container media are first crushed and then heated until the vaporization of combined water expands it to a light powdery substance. Lightness and uniformity make perlite very useful for increasing aeration and drainage. Perlite is very dusty when dry and has a tendency to float to the top of a container during irrigation. It has also been shown that perlite contains potentially toxic levels of fluorine.
Sand
Sand, a basic component of soil, medium and coarse sand particles are those which provide optimum adjustments in media texture
Vermiculite
Vermiculite is a micaceous mineral produced by heating to approximately 745C. The expanded, plate-like particles which are formed have a very high water holding capacity and aid in aeration and drainage. Vermiculite has excellent ex-change and buffering capacities as well as the ability to supply potassium and magnesium. Although vermiculite is less durable than sand and perlite.
Calcined Clays
Calcined clays are formed by heating montmorillonite clay minerals to approximately 690C. The pottery like particles formed are six times as heavy as perlite. Calcined clays have a relatively high cation exchange as well as water holding capacity. These inorganic soil amendments are generally utilized to increase the number of large pores.
Expanded Polystyrene
Polystyrene flakes, a bi-product of polystyrene processing, are highly resistant to decomposition, increase aeration and drainage and decrees bulk density. Polystyrene may be broken down by high temperatures and by certain chemical disinfecting agents.
Urea Formaldehydes
This material is prepared by mixing are with a liquid resin and allowing to cool. Urea formaldehyde forms have a greater water holding capacity than polystyrene but are similar in their influence on aeration and drainage.