Some suggestions from my modeling bibliography:
CORN
cornfields from artificial turf Mod RRer Apr93 p.120
corn w Astroturf Great Model Railroads 2008 p.49
cornfield from bread tie wrappers NMRA Bull Feb83 p.31
corn stalks ModRRer Aug94 p.104
from plastic asparagus fern Mod RRer Apr81 p.98
cornfield w Busch HO kit Model Railroader Sept06 p.40
farm field, for cotton, grapes, strawberry, tomatoes or cabbage, using thread and foam
Model Railroader Mar2010 p.30
farm- soybeans with Faller scenery mat Model Railroader Oct09 p.32
farm- wheat field with Busch plastic wheat stalks Model Railroader Oct09 p.32
GRASS
dead grass along r.o.w. after weed control Model Railroader Mar08. p.55
fake fur Model RRer Aug96 p.86
felt grass & weeds ModRRer Jan82 p.118
grass patches from 3M synthetic steel wool ModRRer Aug98 p.82
grassy clumps w pot toppers Model Railroader Sep10 p.28
knee-deep grass, modeling w/ “Silflor” a new German product
ModRRer Feb 2001 p.72
meadows w elevtrostaticf applicator Model Railroader Sept 07 p.71
prairie grass, from fake fur stuck in plaster and pulled out the
wrong way through the back. N Scale NovDec99 p.47
&