holds excess nutrients rather than letting
them remain too concentrated in the water.
For this reason most commercial mixes
contain peat moss. It is very acidic and will
lower the pH of the medium so that it
should compose no more than 20% of the
mix.
STEER MANURE - is fairly rich in
nitrogen and other nutrients including trace
elements. It holds water well. Many growers
swear by it. Unless it is pasteurized, it may
contain insect eggs and other pests.
BARK - is lightweight, absorbs water
and holds air in its pores. As it comes in
contact with fertilized water it slowly
deteriorates, becoming more of a compost.
It is used extensively by commercial
greenhouse growers. It can be substituted
for lava and it weighs much less.
THE SUBSTRATES
Substrates have recently become the
hot end of the medium market These are
materials which come in a solid form,
usually a block, and need no pre-
preparation. They are just placed in the
growing chamber and watered. They are
inert; sterile and hold water and air well.
Most experiments show that plants do
better in these mediums than in most
mixes. Transplanting substrates is very
easy. The smaller used piece is placed on
top of the larger new piece. The roots grow
into the new block. All of the substrates
support fast vigorous growth.