Whenever, upon the conviction of any person eligible for probation under the preceding section, it shall appear to the satisfaction of the court that the character of the offender and the circumstances of the case indicate that he is not likely again to commit crime and that the public good does not require that he be fined or imprisoned, the court, upon application or of its own motion, may suspend the imposition or execution of sentence and release the offender on probation for such period and upon such conditions as are provided by this article; but in no case, except as provided by the following section, shall the court have authority to suspend the execution of a sentence after the convicted person has been imprisoned for sixty days under the sentence. Any person released on probation must participate as a condition of probation in the litter control program of the county to the extent directed by the court, unless the court specifically finds that this alternative service would be inappropriate.