Just went to a workshop on native grasses yesterday in Cedar Grove, NC. Everything they said there made it seem like the NWSG (native warm season grasses), like bluestem, do not require a lot of N. Most research shows that there are not substantial improvements in yield above 90 lbs of N/acre. As long as P and K are at least above "low" in the soil test, they are usually okay as well. pH should be >5.0, if it is there doesn't seem to be a need for lime. They don't advise N addition if it's in the first year of establishment. Not sure how helpful this is but I'd probably take a soil sample/test before adding any fertilizer/lime!!