The Collaborative International Dictionary of English v.0.48:

Geoponic \Ge`o*pon"ic\, Geoponical \Ge`o*pon"ic*al\, a. [Gr. ?;
   ge`a, gh^, earth + ? toilsome, fr. ? labor: cf. F.
   g['e]oponique.]
   Pertaining to tillage of the earth, or agriculture.
   [1913 Webster]