It is the ecconomy. Harvest have been above average around the world the past few years. In turn supply and demand puts prices low. one bad year and harvests will be down and prices way up.
i've been working for John Deere for 15 years - I have seen this cycle several times already. people blame various politics when it happens, but the fundamentals are enough to explain nearly all of this. Anyone in farming knows this and plans for it (not always successfully)