One problem is that farmers often consider it a secret they don't want to share. For good reason, if you know how much crops will produce next fall you can go to commody markets and make a lot of money. That money comes out of the farmers potential profit in some cases as they are playing the other side of the trade and so the less you know compared to them, the better the deal they can get.
Farmers know what is in their fields, but prices are affected by fields on other continents which the farmer doesn't know. Any information the farmer can get but you cannot is to his advantage. (this applies to all farmers, they need to know what happens in Ukraine, Brazil, Australia... But they need you to not know)