Coco Substrate Buffer
(Used for preparing non-buffered coco substrates such as compressed coco blocks)
Calcium Nitrate 290 g/l
Magnesium Nitrate 280 g/l
Magnesium Sulphate 10 g/l
Ferric EDTA 2 g/l
Make 1L by beginning with 500ml of RO (demineralised) water. Add ingredients one at a time, dissolving each ingredient before adding the next. When all ingredients have been added, top up to 1000ml (1L) with RO water.
What I recommend you do is hydrate the coir blocks in mains (tap) water. That is, fill a bucket or tub with mains water. Measure the EC of the mains water before adding the compressed coir block/s. Lets say its EC 1.0 for arguments sake. Add the compressed coir block and allow it to expand. Stir the water and coco substrate around and then measure the EC again. Youll no doubt find the EC is now much higher. OK, now run mains water through the coir (you may find a bucket with holes and mesh at the base helps here). Run the mains water through (flush) the coir until the water that has passed through the coir (runoff) is no more than EC 1.0 - 1.2. I.e. Original mains water EC ideally matches that of the runoff.
Now fill up a bucket with demineralised (RO) water and dilute the buffer concentrate to 1.4 EC (700ppm). Place the hydrated/expanded and water flushed coir into the diluted buffer solution and leave to soak for at least one hour.
After one hour or more, take out the now buffered coir and squeeze out the excess fluids so the coco substrate is not saturated/water logged. You may find drying it in the sun for a while helps. .
Ready to go you now have a high quality buffered coir product at a fraction of the cost that you would pay for similar products through stores. Id also recommend that you mix the coir with perlite. 60% coir to 40% perlite when using it as a run to-waste medium.
Tip: Many of the compressed coco blocks that are purchased through gardening centres are (when uncompressed) coco powder. If this is the case, look for varying grades of coco substrate, working from fine to larger fibres and mix them into a single product to increase air porosity within the media.
Perlite
Each particle of perlite consists of tiny air cells that provide for a large surface area. Because of the shape of perlite, large air gaps form between the particles. This means there is plenty of oxygen available to the root system.
Perlite doesnt compact and because of this maintains an ideal balance of oxygen and water (oxygen moisture ratio).
Perlite is very tolerant to overwatering which makes it very forgiving medium. Because of its nature, perlite allows excess water to drain off and provides an air ratio of approximately 45%.
Perlite, like coco, has thermal insulation qualities, which provides the root zone with a high degree of security against heat.
Perlite is a very cost effective medium. It is about half the price of expanded clay.
Clay Balls/Expanded Clay (e.g. Hydroton) and Coco Substrate
Ive noticed on internet forums that many growers speak of using expanded clay instead of perlite when working with coco substrate and RTW growing.
Other than this, many growers seemingly use expanded clay at the base of the pots to allow for better drainage (not a bad idea). That is, they line the base of their pots with expanded clay to perhaps two to three inches and then fill the pots with a mixture of coco substrate and expanded clay.
I personally cant see a problem with using expanded clay with coco substrate other than perlite has a higher air capacity than expanded clay (45% versus approx 30 - 35%). Other than this expanded clay offers the roots less security than perlite and is an effective conductor of heat.