At the dispositional hearing, the court shall consider the plan submitted pursuant to section 71-1125, the arguments of the parties, and any other relevant evidence. The Nebraska Evidence Rules shall not apply at the dispositional hearing. The plan shall be approved by the court unless it is shown by a preponderance of the evidence that the plan is not the least restrictive alternative for the subject. After the hearing is completed, the court shall issue an order of disposition placing custody of the subject with the department and setting forth the treatment plan for the subject. The court shall establish the duration of the court-ordered custody and treatment of the subject, but such duration under the initial order shall not be longer than one year.