There are two different crops trading, "old crop" and "new crop", and they are not deliverable against each other. With nov, you are betting on this year's weather, harvest conditions, crop condition, etc. for beans still in the field, and we are looking at a big crop. Nov contract is the first chance people get to speculate or hedge on the crop that is actually growing, so it has a lot of interest. With Aug & Sep, you are betting on sales of already harvested beans that are in the silo, in known condition. They are really two different things.
Jessie