Junkyards. Two or more abandoned, disabled, dismantled or partly dismantled vehicles allowed to remain on a premises for a period of more than 30 days shall constitute a junkyard. Also the storage, sale or abandonment of wastepaper, rags, scrap metal or discarded materials or the collecting, dismantling, storage, salvaging or abandonment of machinery or vehicles not in operating condition shall constitute a junkyard and is a violation of this chapter. When located in an A District, the storage of agricultural equipment, machinery and vehicles which are being used in farm operations shall not, for the purposes of this chapter, constitute a junkyard.