"Title 7 of the U.S. Code and CIPSEA (Public Law 107-347)" are mentioned with regard to confidentiality. I do not see a mention of the specific law that requires my response.
Well, I’d sit on it. If they won’t tell you what US code is behind this, I see no reason to comply. If someone does visit, pull it out and insist on the US code that requires this. Tell them it’s an invasion of privacy, you have no commercial business, and what you grow for your own consumption is your own business. At least, that’s what I’d do.
No matter what’s in it, it must comply with the Paperwork Reductions Act.
http://www.archives.gov/federal-register/laws/paperwork-reduction/