Whenever any board or officer shall issue warrants under the authority prescribed in Kan. Stat. Ann. § 79-2941, the said board or officer is authorized and empowered to fix the rates of levy in such district which will raise an amount of money sufficient to pay and discharge such warrants. Such rate of levy shall be in addition to the rate authorized or limited by law at the time of making such levy: Provided, That the amount of such warrants shall not exceed by more than fifty percent the amount of money that could be raised by taxation in any such district for the year in which the indebtedness represented by the warrants was incurred.