The USDA definition of a farm is as follows:
The definition of a farm employed by the USDA for data collection purposes is "any operation that sells at least one thousand dollars of agricultural commodities or that would have sold that amount of produce under normal circumstances."
With the exception of local zoning ordinances that might be in play there is really no process to "declare" your property as an offical farm. Depending on your business plan regarding the start of a truck farm enterprise you may want to consult with your accountant to discuss IRS regulations that might come into play as you will probably want to deduct business expenses on your tax return.
In this case there is probably no argument that your property is a farm, however, you may need some clarification concerning the interpretation of your farm business for tax purposes.
It is difficult to accurately assess your situation from a 1 line question so please feel free to follow up with more questions as needed.
