Most often, you need to add fertilizer to potting mix.

Some possible explanations --
Drying rate in pots is faster. Super Soil is likely to dry faster than garden soil. Potting soil heats up, sometimes excessively. And lots more possibilities.

Beyond that we need more info about your "test." For instance, in \pots or the ground? and how did you do that?

And SuperSoil makes a number of different soil products so which one did you use specifically? EX: their SuperSoil Garden Soil is not intended for containers as it compacts heavily which would explain your results. It is intended to use as an in-ground garden soil amendment. Same thing is true for Miracle Grow Garden Soil vs. their various types of potting/container mixes.

Dave

I used Super soil potting soil.
They are in f gallon pots.

I have already tested the moisture of the soils but one of the native soils, sandy soil, Had less Moisture, though grew bigger. I was gooing to test the heat but since I already did the experiment, and it is windy now the temp. will be cooler.

Any more ideaas that can explain the odd results.

Thanks,
Andrew

any?

Your soil, no matter what type, is alive with a microherd to some extant. This in turn helps the plants grow, helps feed them, protect them, in short it sort of lives alongside in a scratch my back, scratch your back kind of thing. It is also better regulated than a container. If you want a super container mix, LMK I will give you one that will blow your socks off, and will produce the best looking plants you have ever seen. TImO

Rootdoctor, tell us!

Yes, please tell us Rootdoctor! I just cleared a garden spot where my soil is mostly sand and organic material does not stay a season in the hot soil of our weeks of over 100 temps.

It was said: "organic material does not stay a season in the hot soil of our weeks of over 100 temps."

That's normal. Either mix in more or add, and maintain, a 2-inch thick layer of compost on the soil surface.