As this FT article shows, agriculture exchange would resolve two problems that have hampered farmers from growing their farming as a business:
1. Pricing: many farmers especially those dealing in perishable horticulture produce typically rely on rumours on what prices are. An exchange close to home will be able to relay the information much more cheaply
2. Transport: never mind the roads, due to (a) lack of enough cars (b) fuel costs; farmers typically have to shoulder the costs wrought by these two factors thus minimising their returns.