I have one of those lights, I prefer not to use it because it makes a lot of heat, and since it's so big it doesn't transmit the lumens too great, which is why I use the smaller 23w 2700k cfls in the splitters, this works for me because I can hang the 2 light fixture at any height in the grow cab, or you can just use the one 68w on a chain, and for some reason I really want to hang that light sideways.

you should be ok in the soil, just stay on top of watering it, and don't overwater, the roots need oxygen to spread, so don't drown 'em.

In fact, I'm going to go do a test with the light meter I have. Just as I thought, the 68w doesn't cast the light any better than the 2x23w, at 5 inches from the light both read 200 on the meter. So in this bulbs case, the more wattage doesn't make for better light output, maybe overall, yes, but that light is like 8" tall by 3.5" wide, that's quite a bit of surface area to be projecting light from.

I'm gonna stop ranting now but I hope this helps!