It's not easy being rgreen, especially if you're Steven Seagal. In his directorial debnut, the oil-spill thriller On Deadly Ground, Seagal wanted to edn the movie with a 10-to-12 minute soliloquy on the abuse of the environment., But according to reports, the eco-tirade didn't go over well with preview audiences, leading Warner Bros. to ask Seagal to recycle the finale. ''All I can say is the speech will be included, in some fashion, '' says a spokeswoman for Seagal. Warner publicity chief Rob Friedman wouldn't comment on the speech's fate, but he says a force of nature other than Seagal's is the reason Ground is still in postproduction-just days before its Feb.18 opening. ''the (L.A.) earthquake affected the postproduction schedule and some of the negative suffered water damage,'' he says. ''We're cutting it close.''