Bagging Soil?

My grow cabinet is a pretty confined space. I have been notcing how quickly the lights dry up my soil (almost once a day). I was thinking I can place a ziplock bag over the soil and around the plant to form a sort of humidity dome, thus retaining water better. Is this a bad idea?

Does the soil just get dry on the top or when you put your finger in 3 inches do you still feel it being dry?

If it's only on top, just mist with a spray bottle.

you could but it may cause mold....ad vermiculite to the soil....

Are they seedlings? You could use a clear two liter bottle and cut off the bottom to create a dome...