slit in tire

[RuT]

I have a NH TC29D 4x4 with R4. The thing only has 50 hrs on it and I noticed today a slit in the tire. It is near the center and has a 1" slit in the outermost rubber, not in the tread. There seems to be a harder rubber underneath it and it is not leaking any air.

Should I be doing anything to this almost new tire to make sure it lasts? Is there a way to seal that 1" slit? Will it spread?

 

[RoyJackson]

When I first looked at my 670, both front tires had slits on the sidewalls. The tread was good.
However, part of the deal was to replaced those tires.
I would, at least, have a tube installed.