The Collaborative International Dictionary of English v.0.48:

Grainfield \Grain"field`\ (gr[=a]n"f[=e]ld`), n.
   A field where grain is grown.
   [1913 Webster]

WordNet (r) 3.0 (2006):

grainfield
    n 1: a field where grain is grown [syn: grainfield, grain
         field]

U.S. Gazetteer Places (2000):

Grainfield, KS -- U.S. city in Kansas
   Population (2000):    327
   Housing Units (2000): 159
   Land area (2000):     0.473686 sq. miles (1.226842 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.473686 sq. miles (1.226842 sq. km)
   FIPS code:            27200
   Located within:       Kansas (KS), FIPS 20
   Location:             39.114101 N, 100.467540 W
   ZIP Codes (1990):     67737
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Grainfield, KS
    Grainfield