Territory annexed to a city pursuant to petition to the director of the office of administrative hearings is annexed as of the date of the order of the administrative law judge, except for tax purposes, and a copy of the resolution with an accurate map of the annexed area, certified by the executive officer of the city, must be filed and recorded with the county recorder. Annexation is effective for the purpose of general taxation on and after the first day of the next January. However, the city shall continue to classify as agricultural lands for tax purposes all lands in the annexed area which were classified as agricultural lands immediately before the annexation proceedings until those lands are put to another use.