Hydroponics

Hydroponics (from the Greek words hydro (water) and ponos (labour)) is a method of growing plants using mineral nutrient solutions instead of soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel or mineral wool. A variety of techniques exist.

Plant physiology researchers discovered in the 19th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics, but some will do better than others. It is also very easy to do; the activity is often undertaken by very young children with such plants as watercress. Hydroponics is also a standard technique in biology research and teaching and a popular hobby.

Rockwool
Rockwool is probably the most widely used medium in hydroponics. Made from basalt rock it is heat-treated at high temperatures then spun back together like candy floss. It comes in lots of different forms including cubes, blocks, slabs and granulated or flock.
Rockwool is an excellent inert substrate for both 'free drainage' and recirculating systems. In free drainage or run-to-waste systems, the chance of disease spread is greatly lessened. Rockwool is also lightweight and self-contained, which allows plants to be grown at different densities in different stages - young plants can be grown to an advanced stage in a small area before being planted out into the main growing area, thus improving crop turnaround. Its light weight also permits setting up to be quick and inexpensive. Because it is light and rigid it eliminates back-breaking work in preparation and planting and gives substantial labor-saving costs. Rockwool is noted for providing a favourable root environment, thus minimizing plant stress. Root temperature can also be controlled, thus giving substantial energy savings. Rockwool initially causes an increase in pH level. You must adjust the pH level of the nutrient solution to counteract this. A pH level of 5.5-6.5 should suffice to create a suitable pH.
Before handling, gloves and long shirt sleeves should be worn to prevent minor skin irritation. This can also be lessened by wetting the rockwool before handling. When this medium is dry, care needs to be taken so as not to inhale any particles; inhaling such particles may carry a health risk.

Coir
Coco peat, also known as coir or coco, is the leftover material after the fibres have been removed from the outermost shell (bolster) of the coconut. It took 10 centuries to make this waste a viable plant substrate. The first description of the coco process dates from the 11th century and was recorded by Arabian traders. In 1290, Marco Polo described the process of extracting fibres from coconuts.
Coco is a 100% natural grow and flowering medium, which has proven its value across years and years. Coco is not only a high quality product, but also an environmentally friendly product. This and the unique growth characteristics ensure coco is the medium of the moment and the future.
Some types of coir are very high in sodium (salt) due to the nature of coconut palms growing on island environments and being processed in the salt air. Quality coir has not been sterilized or heat treated and so retains its natural sponge-like qualities as well as the natural, beneficial trichoderma fungi which has been scientifically shown to combat root rot and other diseases. Trichoderma is also well-known for promoting root growth.
This substrate combines the tolerant, organic nature of soil with the precision of rockwool. Due to the special characteristics of the substrate the nutrient doesn’t have a grow and flower variant, there is just one unique formulation for both growth and blooming phase. Due to the unique buffering capability of the coir substrate, and its sponge-like structure, the nutrients needed to ensure high yields are stored in the coco. This means that the plant itself can regulate the amount and timing of its nutrient intake.
Coconut fibres have sufficient capillary action to retain enough water and nutrients. This means that the plant can go for longer periods with-out water, which could happen if a feeding pump was to break down for example.
Quality coir can be used a number of times and makes an excellent soil improver after use.

Perlite
Perlite is a volcanic rock that has been superheated into very lightweight expanded glass pebbles. It is used loose or in plastic sleeves immersed in the water. It is also used in potting soil mixes to decrease soil density. Perlite has similar properties and uses to vermiculite but generally holds more air and less water. If not contained, it can float if flood and drain feeding is used.