26 C.F.R. § 1.268-1
In computing taxable income no deduction shall be allowed in respect of items attributable to the production of an unharvested crop which is sold, exchanged, or involuntarily converted with the land and which is considered as property used in the trade or business under section 1231(b)(4). Such items shall be so treated whether or not the taxable year involved is that of the sale, exchange, or conversion of such crop and whether they are for expenses, depreciation, or otherwise. If the taxable year involved is not that of the sale, exchange, or conversion of such crop, a recomputation of the tax liability for such year shall be made; such recomputation should be in the form of an "amended return" if necessary. For the adjustments to basis as a result of such disallowance, see section 1016(a)(11) and the regulations thereunder.
26 C.F.R. §1.268-1