^somewhat true, yes some farmers spray twice a year but if they only spray once in the spring you will be fine because the chemical that they spray (glyphosate) is only effective if it is sprayed directly upon the leaves of a plant so there is no risk of residual chemical in the soil. i also dont know of any farmers who still do "crop dusting" for corn. I live in MN idk how farming is done in other areas tho.
Also no farmers will walk more than 10-20 rows into the corn field so plant them a ways in and you'll be fine.
Also harvesting is a very weather dependent activity, you cannot begin harvesting until the soil is dry enough or frozen, by the time it is frozen your plants will be done. It is all very weather dependent tho, if the weather is shitty, wet, and warm in october,november you could be okay but if it is dry or the ground freezes you there is a chance of your plants getting combined.
this however is just the situation in MN, im not an expert on agriculture in other areas, I guess im not an expert on MN ag either but i do know enough since i have lived on a crop farm my entire life