Whenever any defendant shall appear for sentence before a district court, the court may impose a sentence and suspend its execution, or place the defendant on probation without the imposition of a suspended sentence. The defendant may be placed on probation for the time and on any terms and conditions that the court may fix. The period of probation, together with any extension, shall not exceed one year, except that probation may be for a longer period in cases in which the district court may by law impose a sentence longer than one year; provided, that the period of probation shall not exceed the longest sentence which the court may impose.