They won't hold as well as corn, but unless you have an open top feeder you needn't worry about it. Any farmer's around your area? They probably won't mind selling you a bushel or garbage can at a time as long as you shovel it yourself They still get there price and they don't have to pay transportation costs.

Side note, if they do get wet enough to get "mushy" THROW IT AWAY...FAR FAR AWAY!!!! Rotten soybeans will near make me vomit (and I used to steam-wash hog barns!!). It starts out sweet and musty, then turns to flat rancid.[:'(]