I don’t know the answer and I think it’s the wrong question for the situation. If you do have answer, please share it.

There is a large price spread between US and South American soy beans. If the drop in US prices were because of a bumper crop in South America, then you’d expect the price in South America to drop at the same time. That’s not necessarily guaranteed to happen since just a few months ago, South American export prices were substantially higher than US export prices. I don’t know if export prices have dropped in South America. The most recent month of data I can find is May 2018.