Miracle Gro Potting Mix is what Miracle Gro calls their potting soil. Miracle Gro also has Garden Soil Varieties as well.
I think what he's testing here is the effects of the Moisture Control versions of the potting mixes/soils have on the Plants.
<a href="http://i161.photobucket.com/albums/t215/Sloppy-G/realrando.jpg" target="top"><img src="http://i161.photobucket.com/albums/t215/Sloppy-G/realrando.jpg" height="450">
http://www.miraclegro.com/index.cfm/...oducts%2FSoils
I'm pretty sure what kills the plants are the Moisture-Control, Yellow fert balls that contain an excessive amount of Nitrogen wich is really good for flowers and vegetating plants. However, when plants are producing reproductive biomass (tomatoes, peppers, buds, e.t.c.), the require a minimal concentration of Nitrogen, and greater ammounts of vitamins, potassium and especially phosphorous.
What makes it worse is that when the plants have so much of a certain nutrient, they completely reduce their overall absorption of nutrition and water as well. What makes this even worse is that the plant is pretty much starving itself, so the symptoms aprear to be malnutrition, and many resort to this by feeding and watering, which progressively makes the issue worse and kills the plants. (That's what I did to a couple of my first plants).
To make things even worse, when the plants dont absorb all the water from the soil (over-watering), the lingering water prevents the plant from absorbing oxygen from the roots while bacteria collects because of the pooling water, which can quickly rot the roots and kill the plants in a matter of days.
VTec's experiment should just be really helpful, although there's a huge bias towards the Miracle Gro plants, because I would say his growing skills are unrepeatably better than the average grower.
I'm kinda running the same thing right now, but just so I can make my personal decision about the matter.
Keep it up SmknVTEC