Living in Western Kansas and working for a large family farm right now.
Most of the farmers around here use the long tube grain storage (1) and store it right on the edge of their fields. Lots of grain stored here across the countryside that probably isn't recorded anywhere.
1. https://www.alibaba.com/product-detail/agricultural-plastic-...
I tried to find out for the EU, but I can't find that either. (The stockpiles/overproduction was one of the favourite criticisms of anti-EU people in Britain.)