I'd spray it with roundup the next opportunity you have, then wait until the vegatation is completely dead (a week to maybe 14 days), then broadcast a little fertilizer (12-12-12 or anything you can get that's balanced) and lime and disk it all in. I'm not really sure what mid Sept is like in La, but here in Kansas that time of the year would be pushing it for being a little too late. So I guess you'd be OK in La.