How does hedging using futures work?
Producers of corn may not be able to afford a decrease in prices.

Remember that farmers are (usually) not speculating and not “investing”. They are producing a product that they need to offload in order to make money. They have zero interest in uncertainty (again, assuming that most are not speculating). The future price they can receive today may be better than the spot price in 6 months, or it may be worse - you really have no idea, but at least you can lock it in, so that you know what to plan for.

Remember that farmers have two uncertainties about their product when laying the first seed: 1) quantity and 2) price. By hedging the price on some quantify you can reduce your risk significantly (and hence also your upside) which may be far more appealing then the risk of losing everything.