Southern MN and Central IA | I would suggest checking with Ohio State's Agricultural Extension Service. They should have plans and guidelines available for storing hay and straw. I know Oklahoma St has done quite a bit of work with that. Below is a link to some of the Oklahoma St work along with Virginia Tech.
Hope this helps!
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2270/BAE...
http://www.ext.vt.edu/news/periodicals/fmu/2003-10/haystorage.html |