I saw this on Facebook, but it had tiny writing, so I dropped it into Photoshop and added some larger text to it. Please note, if I am infringing on anyone's copyright, please let me know and I'll take it down asap.
Note, this will look awkward once I publish it, as it will bleed over into my avatar, but I want the pic large enough to read, so just ignore that, I did it on purpose.
Here ya go folks:
Healthy: Leaves shine with a rich dark
green color when adequately fed.
Phosphate: Shortage marks leaves with
reddish-purple, particularly on young plants.
Potash: deficiency appears as a firing or
drying along the tips and edges of lowest leaves.
Nitrogen: hunger sign is yellowing that starts at
the tip and moves along middle of leaf.
Magnesium: deficiency causes whitish strips
along the veins and often a purplish color on the
undersides of the lower leaves.
Drought: causes the corn to have a grayish-green
color and the leaves roll up nearly to the size of
Disease: heminthospoium blight, starts in small
spots, gradually spreads across leaf.
Chemicals: may sometimes burn tips, edges of leaves
and at other contacts. Tissue dies, becomes whitecap.