The most widely-spread growing medium is, perhaps, rockwool.
Originally used for insulation purposes and also known as mineral insulation,
rockwool was first used as growing medium by Dane gardeners. Now, it is
frequently used for drip-style indoor gardens around the globe.
Rockwool is produced by a process similar to making cotton
candy: a particular mixture of sand and rock is melted and then turned into
fibers by spinning the mixture to form products of multiple shapes and
dimensions, from 1″ starter cubes and up to large slabs of 3″x12″x36″ in size. The variety of available
forms and sizes turns rockwool into one of the most widely-used growing
mediums.
Key advantages, as well as disadvantages, of this popular
growing medium are listed below.
Rockwool’s Strong Points
HOLDING WATeR – rockwool as a growing medium in hydroponics
systems is capable of holding a large amount of water. This creates an
additional protection for situations, when water is not supplied because of
power outages or failures in pumping or other gardening equipment.
ACCUMULATING AIR – up to 18 % of air are constantly kept by
rockwool. Due to this capability, there is a very little risk to over water
rockwool; besides, the plants are always supplied with enough amount of oxygen.
MULTIPLE SHAPES AND SIZES AVAILABLE – whether it is a small
1″ cube for seeds propagation or a large 3x12x36 inches slab for huge plant,
rockwool offers a wide variety of shapes and sizes to choose from. Besides,
loose rockwool is also available, designed for filling different plant
containers.
NO DUST AND EASY TO USE – since rockwool maintains its form
almost perfectly, it cannot be scattered accidentally. Besides, usually packed
into plastic rockwool is a very clean material that is easy and comfortable to
work with.
Rockwool’s Weak Points
NOT A “GREEN” MATERIAL – rockwool is claimed to be not
environment-friendly material, because of its almost indefinite time of
breakdown.
HEALTH HAZARDS – rockwool particles and fibers pose serious
health danger, especially for human lungs. That is why it is necessary to wear
a protective dust mask, while working with rockwoll.
PH PROBLEMS – because of rockwool’s high pH level, it is
necessary to balance pH level in the nutrient solution properly and make it
suitable for the plants, you are growing. In general, the use of rockwool
requires more routine work to keep pH level of your nutrient solution at steady
level.
LONG PRE-SOAK PERIOD – before rockwool can be used in the
hydroponic system, it should be soaked for at least 24 hours beforehand. Other
growing media usually do not require pre-soaking, it is enough just too
well-water them.