Permits required Oct 15 - May 15. None required otherwise, but it's usually a good idea to contact your local forestry office the sheriff's dispatch and let them know what you're up to. Some cities have additional burn permitting requirements. Your county Tenn Division of Forestry office issues permits.
It sounds like this is your first time burning a field- get some experienced help, either from Forestry or TWRA. It can save you a world of hurt.