Farming accounting question!

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Calling all farmers, anyone who has an answer to this can reply below with a comment or email me directly pennysemail@comcast.net.

I have a question regarding farming taxes.  When writing off the expenses of the farm under your farming income, is the entire mortgage eligible as a business expense or do you need to somehow figure out which portion of the mortgage would be for the barns, land, etc?  (In other words, is the whole mortgage deductible as a farm expense?  House too?)

Just wondering, for future use!  :-)