Richard

Rockwool and Hydroton (a rockwool product) are two of several materials that are used in soil-less hydroponics and soil-less drip irrigation.

If you must grow indoors, then hydroponics is a good method of managing the environment. If you are growing outdoors, then hydroponics does not become cost effective with larger plants until you exceed about 2,000 linear feet.

If you are just trying to achieve more drainage in the ground or in pots with a few plants, then consider adding horticultural sand (not construction sand) and 1/4 to 1/2 inch pumice to the soil. If you have clay, then humic acid products can (over time) emancipate the clay bonds and allow minerals to flow to the plants. A soil surfactant can also help with percolation in clay soils. I recommend a natural or synthetic liquid product instead of gypsum because it has a much better chance of penetrating the clay. The synthetic products are actually a better choice over liquid gypsum because clay already contains the Calcium present in liquid gypsum.

If you go with a completely soil-less system, then there is an important fact to understand about plant nutrition: namely, there are no soil minerals present. This means that certain minerals normally obtained from the soil (e.g., Calcium and Magnesium) are not present, and there are no soil microbes to break down certain common types of fertilizer. In particular, fertilizers with the Urea form of nitrogen should not be used because (1) it will not be absorbed by the plants (2) its presence without the microbial buffer can burn roots. There is an urban myth that Urea nitrogen comes from urine. It is true that the chemical was first identified in urine, but several major fertilizer suppliers obtain it from dry lake beds, not sewage systems.

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