Lots of questions lately about what to use for fertilizer and "soil" when growing Fast Plants; questions like this one that came to us yesterday:
I am doing a summer science project on the relationship between the concentration of Miracle-Gro fertilizer and plant growth, I am using your fast plants for this investigation and I would like to know what the recommended fertilizer concentration is for this type of plant. I would also like to know what is in the Carolina Biological Supply mix that is different from regular potting soil?
We recommend 1g/Liter of a 14-14-14 fertilizer mix (we use Scott’s fertilizer, but any 14-14-14 would be the recommended nutrient balance). We often use Osmocote time-release pellets for ease of use (and when fertilizer isn't the variable being tested).
Potting mix contains no soil. Here’s a YouTube video
that describes the difference in the texture: https://youtu.be/eQfJznFDsSk
However, in this video (produced by MiracleGro, the potting mix that they show has added moisture-holding material (a polymer that they add to the mix) plus fertilizer. Keep in mind that it is important if your experiment is testing fertilizer effects, that your planting medium be nutrient-free so that all differences that you observe come from the fertilizer you apply.