There is a very nice Australian site, use to be Manix Botanix, but has changed names to medteknutrients.com.au with comprehensive information on Coco Coir, DTW and more.
Here is a quote from there with the scientific references to help dispel any broscience involved.
"Firstly, let me dispel a common myth and say that coco substrate is a hydroponic medium (largely inert) and is very different from soil. One forum actually went so far as to as to have a thread called “coco and soil growing” –implying that the two very different mediums were almost one and the same thing. Let me put things straight. They aren’t. Coco substrate is coco substrate and soil is soil – the two very different products require two very different treatments/approaches to realise optimum yields. Just one example being that optimum pH in soils lies between pH 6.5 – 6.8, while optimum pH in coco is 5.5 – 5.8. Additionally, an optimised soil nutrient will look very different to a coco coir formulation (we’ll talk more about this shortly).
OK, so let’s put that aside; coco substrate is a hydroponic medium. Soil is soil. That simple!
The next thing that needs to be addressed is that idealised coco nutrient is somewhat different from a standard nutrient due to the organic coco substrate containing often naturally high levels of potassium and (in many cases) sulphates etc. I.e.
Analysis of a High Quality Coco Coir Sample
All figures refer to ppm (mg/L)
Canna Coco Substrate (purchased and tested in the US, September 2011)
Ref: URAYAMA HISASHI (Nihonkokusaikyoryokuse Tsukubashisho) MATTHEWS LORATO J. (Nootigedacht Adc, Ermelo, Zaf) COETZEE VINAL J. (Dept. Agriculture, Zaf) YAMASHITA TADAAKI (Japan International Cooperation Agency, JPN) (2005) Cucumber Cultivation in Energy-Saving Hydroponic System Using Coconut Coir as Growing Media"
