Any nonresidential use which is in, abuts, is adjacent to or is less than 50 feet from any R District, and which is not conducted within a completely enclosed building, such as storage yards, lumber and building materials yards, and parking lots and like uses, shall be entirely enclosed by a fence or landscaping sufficient to effectively shield such uses. This section shall not apply to nurseries, and the display sales purposes of new or used cars, trucks, trailers, bicycles, motorcycles, or farm equipment.