Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances

National Science Foundation [AST-1616636]; National Aeronautics and Space Administration [16-XRP16_2-0004]; Ramon y Cajal fellowship [RYC-2013-14182]; Spanish Ministry of Economy and Competitiveness (MINECO) [AYA-2014-58082-P]; Alfred P. Sloan Foundation; U.S. Department of Energy Office of Science; Center for High-Performance Computing at the University of Utah