The elevators have rail and truck but not barge service; they are thus called inland elevators. I. The applicable legal principles are set forth in our statute and decisions. Code 1971, § 441.21 (all references are to that Code); Tiffany v. County Board of Review in and for Greene County, 188 N.W.2d 343 (Iowa); Juhl v. Greene County Board of Review, 188 N.W.2d 351 (Iowa); and Maytag Co. v. Partridge, supra. The ultimate question in tax valuation cases is the exchange value of the property as a unit — what it would bring between a willing buyer and willing seller if offered for sale. The exchange value may thus be equated to the market value.

Under the statute, it then became the Board's burden to uphold the valuation as reasonable and proper. Wunschel v. Board of Review, 217 N.W.2d 576, 578 (Iowa 1974); Juhl v. Greene County Board of Review, 188 N.W.2d 351, 353 (Iowa 1971). As we understand the trial court's decree and the Board's appeal therefrom, the decisive question to be decided is whether the Board sustained this burden.

Section 441.21, The Code; Tiffany v. County Bd. Of Rev. In And For Greene Co., 188 N.W.2d 343 (Iowa 1971); Juhl v. Greene County Board of Review, 188 N.W.2d 351 (Iowa 1971). The burden of proof is upon the complainant attacking the assessor's valuation, but in protest or appeal proceedings where the complainant "* * * offers competent evidence by at least two disinterested witnesses that the market value of the property is less than the market value determined by the assessor, the burden of proof thereafter shall be upon the officials or persons seeking to uphold such valuation to be assessed."

The statute makes relevant a fair and reasonable exchange in the year of the assessment. Sale price of the subject property or comparable property in normal transactions reflecting market value and sale price of property in abnormal transactions adjusted to reflect market value may be considered. Juhl v. Greene County Board of Review, 188 N.W.2d 351, 352-53 (Iowa 1971). Even one of the comparable sales relied on by the board's valuation witness, Donald Wehr, to support the assessor's valuation occurred in October 1977.

The appellant learned of the property through an advertisement in a Cedar Rapids newspaper and purchased it after it had been on the market for approximately six months. Second, there is evidence of both a sale of the subject property and comparable sales so as to require that a comparable sales approach be utilized in valuing the property Milroy v. Board of Review, 226 N.W.2d 814, 819 (Iowa 1975); Juhl v. Greene County Bd. of Review, 188 N.W.2d 351, 353 (Iowa 1971) The board of review presented two expert witnesses who valued the property higher than the assessor's valuation for 1992 and another witness who valued it lower than the assessor's valuation but above the January 11, 1992 sales price.

In Bartlett Company Grain v. Board of Review, 253 N.W.2d 86, 87-88 (Iowa 1977), we dealt with appeals involving the valuation of inland elevators and had the following to say about the legal principles involved in such cases: "The applicable legal principles are set forth in our statute and decisions. Code 1971, § 441.21 (all references are to that Code); Tiffany v. County Board of Review in and for Greene County, 188 N.W.2d 343 (Iowa); Juhl v. Greene County Board of Review, 188 N.W.2d 351 (Iowa); and Maytag Co. v. Partridge [ 210 N.W.2d 584 (Iowa)], supra. The ultimate question in tax valuation cases is the exchange value of the property as a unit — what it would bring between a willing buyer and willing seller if offered for sale. The exchange value may thus be equated to the market value.

Thus, admission of evidence concerning replacement value and depreciation was proper. As stated in Juhl v. Greene County Board of Review, 188 N.W.2d 351, 352-353 (Iowa 1971), section 441.21 "* * contemplates the willing buyer-willing seller standard shall be first used. Other denominated methods may be used only if the property has no readily ascertainable market value under the buyer-seller test. Stated otherwise, the assessor (and later the court) may use one or more of the formulae based on productivity, earning capacity, industrial condition, cost, depreciation and the like if, and only if, the market value cannot be readily ascertained, under the willing buyer-willing seller formula.

21, The Code (1966), we have reviewed valuation and assessment disputes in a number of cases. See Power v. Regis, supra; Wunschel v. Board of Review of Carroll County, supra; Maytag Company v. Partridge, 210 N.W.2d 584 (Iowa 1973); Juhl v. Greene County Board of Review, 188 N.W.2d 351 (Iowa 1971); and Tiffany v. Greene County Board of Review, 188 N.W.2d 343 (Iowa 1971). In addition to these, defendants rely heavily on Daniels v. Board of Review, 43 Iowa 405, 52 N.W.2d 1 (1952).

I. Our review is de novo. See Maytag Company v. Partridge, 210 N.W.2d 584, 595 (Iowa 1973); Juhl v. Greene County Board of Review, 188 N.W.2d 351, 353 (Iowa 1971). Weight is accorded trial court's findings but we are not bound by them.

We there laid down the rule that in valuing improved real estate, an assessor is not to value the land and the improvements separately and then add the two values together. Rather, he is to value the improved real estate as a unit. See also Juhl v. Greene County Board of Review, 188 N.W.2d 351 (Iowa); Markwardt v. County Board of Review in and for Franklin County, 174 N.W.2d 396 (Iowa). Applying these principles, the law required this assessor first to endeavor to apply the sales prices approach in determining the exchange value of Maytag's Plant 2 — that is, from sales prices of comparable plants.