Table 4.

Important possible growing media (modified after Ter Berg, 2000).

Substrate		Raw material	Characteristics
			AVa	WVb	OMc	Densityd	RDe
			m3 m−3	m3 m−3	g g−1	kg m−3	kg m−3
None	NFT	Nutrient film technique	–	0.99	0	–	–
	DFT	Deep flow technique	–	0.99	0	–	–
	Aeroponic	Foggy nutrient solution	0.99	–	0	–	–
Inert	Sand, gravel, or mixes	Granular material of fine divided rock and mineral particles	0.20 depending on particle size
	Glass wool	Melted silica sand (1200°C)	f
	Foam	Phenolic foam granules based on mineral oil	f
	Rock wool	Melted basalt and lime stone after supply of coke (1600°C)	0.04	0.94	0.02	1900	49
	Lava	Brocken, sieved vulcanic stone	f
	Pumice	Porose, air filled vulcanic stone	0.26	0.57	0.03	2000	431
	Perlite	Morphous volcanic glass	0.52	0.44	0.01	900	105
	Vermiculit	Hydrous silicate mineral	f	0.50		2500	70–100
	Vleece	Polyester, etc.	g
	Clay granules	Decompressed clay (1100°C)			0	1870	489
	Polyurethan	Mix of mineral oil and di-isocyanat	0.35	0.60	0.99	1190	78
Organic	Wood fiber	Pressed wood mill waste	0.62	0.20	0.98	1440	87
	Saw dust	Different origins	g
	Peat		0.14	0.79	0.96	1580	113
	Coco fiber	Different origins	0.55	0.40	0.98		0.77
	Rice husks	Different origins	g
	Composts	Different origins	g

Suitability depends on availability, growing conditions, and experimental goal (Ter Berg, 2000).

^aAir volume;

^bwater volume;

^corganic portion;

^ddensity of the solid matter;

^ebulk density;

^fphysical and chemical characteristics insufficiently known;

^gdepending on origin, produce characteristics may differ significantly.