26 CFR §1.182-5

1. (a)Limitation
   1. (1)General rule. The amount of land clearing expenditures which the taxpayer may deduct under section 182 in any one taxable year is limited to the lesser of $5,000 or 25 percent of his “taxable income derived from farming”. Expenditures in excess of the applicable limitation are to be charged to the capital account and constitute additions to the taxpayer's basis in the land.
   2. (2)Definition of “taxable income derived from farming”. For purposes of section 182, the term taxable income derived from farming means the gross income derived from the business of farming reduced by the deductions attributable to such gross income. Gross income derived from the business of farming is the gross income of the taxpayer derived from the production of crops, fruits, or other agricultural products, including fish, or from livestock (including livestock held for draft, breeding or dairy purposes). It does not include gains from sales of assets such as farm machinery or gains from the disposition of land. The deductions attributable to the business of farming are all the deductions allowed by Chapter 1 of the Code (other than the deduction allowed by section 182) for expenditures or charges (including depreciation and amortization) paid or incurred in connection with the production or raising of crops, fruits, or other agricultural products, including fish, or livestock. However, the deduction under section 1202 (relating to the capital gains deduction) attributable to gain on the sale or other disposition of assets (other than draft, breeding, or dairy stock), and the net operating loss deduction (computed under section 172) shall not be taken into account in computing “taxable income derived from farming.” Similarly, deductible losses on the sale, disposition, destruction, condemnation, or abandonment of assets (other than draft, breeding, or dairy stock) shall not be considered as deductions attributable to the business of farming. A taxpayer shall compute his gross income from farming in accordance with his accounting method used in determining gross income. (See the regulations under section 61 relating to accounting methods used by farmers in determining gross income.)
2. (b)Examples. The provisions of paragraph (a) of this section may be illustrated by the following examples: