The Collaborative International Dictionary of English v.0.48:
overcrop \overcrop\ v. t. to exhaust (arable land) by excessive cultivation. Syn: overcultivate. [WordNet 1.5]WordNet (r) 3.0 (2006):
overcrop v 1: to exhaust by excessive cultivation; "the farmers overcropped the land" [syn: overcrop, overcultivate]