You can bale anything wet, but it is usually a bad idea. Back in the early 60’s my brother & I helped put up a LOT of green, wet & HEAVY alfalfa. We packed the loft of a very large barn. It generated enough heat and gas that it burned the place to the ground. Largest fire I had seen to that date /forums/images/graemlins/shocked.gif.
I ran a hay crew years ago. Stored 5,000 bales of wheat straw in a big old barn. Filled the loft and all of the side stalls. Only thing open was the alleyway. The owner then baled some oats wet and asked me to pile them in the alleyway. I argued with him to the point of him saying if I didn't want to do it he would find someone else. I said okay, I'll do it but you are probably going to lose your barn. We pilled the alleyway full and shut the doors. A week or so later it burned to the ground. This guy was trying to make sileage. he just didn't have it airtight enough. As KennyV said it was the biggest fire I have ever saw. The property is East of my house 3 1/2 miles and the glow from the fire woke me in the middle of the night and I went and helped them save their house.
If you do this project, don't commit your barn to it!!!!