Have the farmers declare what they are planting. Then other farmers can see if one crop is being over planted and grow something else. If planting totals were declared the over/under planting of crops would be reflected in the futures market and farmers could adjust.
What you describe is indeed a part of every ‘farm bill’ that is considered to be a subsidy to farmers.
USDA record-keeping, estimates, and predictions are almost daily news in farm country.