I think it sounds like an interesting project. He could use an expensive brand, a similar fert but without the big name and price, then a couple organics, maybe a time-release type, and some with no fert at all. If there are no noticeable differences that would be even more interesting!

Be sure to let us know how it turns out.

Kate

I am a teacher, and we did an experiment like this last year in my 4th grade science class. It went like this:

We took two common Dieffenbachia plants, both potted in ordinary (no added fertilizers) potting soil. Over a period of weeks, we added some all-purpose fertilizer to just one of the plants. Both plants were getting the same regular water and sitting in the same windowsill. The fertilized plant seemed to put on a little more growth. Nothing outstanding.

Then, after 6 weeks or something like that, we stopped watering both plants, and watched to see how long it took for signs of distress to appear. The results were striking. The plant without fertilizer quickly started to droop and turn brown with no water. The fertilized plant kept its color and form many times longer, only starting to show stress about the time that the other plant looked almost completely dead. It was interesting.

Hope that gives you some ideas. Heck, take the whole experiment if you want. I hope your son does well.
good luck!

Contact your local Extension Agency .
Try searching on solutionsforyourlife.com .
They will have lots of info and help .
This is right up their alley .