The Census Bureau operates many surveys for many different depts, including the agricultural one you are talking about. How do you think you get the unemployment rate? The health statistics to monitor cancer clusters, etc... The fishing and wildlife to find out if there is a need for more rangers/parks and such. And on and on.
Being paranoid of surveys that have been around since the 40’s and 50’s is just asinine. And the purpose of the Census conducting is the privacy that the constitution affords you. Not even the IRS can access your data from these surveys. Hell, you don’t even have to give your real name.
I don't think I'd bet my life, livelihood or future on that.