A "row" is measured in inches center of the planted crop to center of the planted crop. Standard in most of the corn belt for corn is 30".  However it may be anywhere from 18" to 38" or 40".  The standard for soybeans is getting to be 15" with a range from 7 1/2" to 30".  I believe in beet growing areas 22" is more standard for both.  I'll let someone else speak to that.

Row width is roughly set by the equipment used to plant, maintain, or harvest the crop. Most corn is in 30" because it is narrow enough to provide good canopy and yet allow tractors to get down the row

Remember these are generalities.  There is always the exception or regional difference.  Gotta run.