Honestly, they already know -- most farmers these days have college degrees in soil science or agribusiness or horticulture or whatever. After all, most farms are owned by Big Ag and they've presumably got the same "we just immediately shred your resume if you don't have at least a bachelor's, whether the job actually needs it or not" applicant gatekeeping standards as the rest of corporate America.
If they're not doing the sustainable thing it's not because they're ignorant, it's because it's less profitable than the unsustainable thing and they're choosing the shortsighted option on purpose.