Under section 175, a farmer may deduct his soil or water conservation expenditures which do not give rise to a deduction for depreciation and which are not otherwise deductible. The amount of the deduction is limited annually to 25 percent of the taxpayer’s gross income from farming. Any excess may be carried over and deducted in succeeding taxable years. As a general rule, once a farmer has adopted this method of treating soil and water conservation expenditures, he must deduct all such expenditures (subject to the 25-percent limitation) for the current and subsequent taxable years. If a farmer does not adopt this method, such expenditures increase the basis of the property to which they relate.