Agricultural Bank Assistance Act of 1986 - Amends the Federal Deposit Insurance Act to require Federal banking agencies to permit an agricultural bank to: (1) amortize over ten years any loss on a qualified agricultural loan that the bank would otherwise be required to show on an annual financial statement for 1985 through 1987; and (2) reappraise the value of any real estate or other real or personal property that the bank acquired coincident to making a qualified agricultural loan and that it owned on January 1, 1985, and any additional property that it acquired before January 1, 1988, and to amortize over ten years any loss resulting from such reappraisal that it would otherwise be required to show on its annual financial statements. Allows such amortization: (1) only if there is no evidence that fraud or criminal abuse by the bank led to such losses; and (2) unless the appropriate agency first determines that the bank is insolvent.