Fescue Hay - smells like tobacco?

In the past I've gotten mixed grass hay from a guy who said he never sprays or does anything to that unused field - worked well for me.  This year I was too late and found another guy who had fescue hay.   He assured me several times during discussion of organics and no till farming, that it had not been sprayed.   So I came home and stacked it in the garden until the weekend.   When I went out there the next day the garden smelled sweet and pungent.   Couldn't figure out where it was coming from until a few days later when I started moving the hay.   I apply half thickness solid flakes to my vegetable beds in the fall and again around my vegetables in Spring.   This hay is very nice texture, still soft and slightly green,   but as I worked with it my nose became watery and my eyes burned a tiny bit.   It dawned on me that the smell reminded me of tobacco (which I quit smoking 25 yrs ago :)   It's been over a month now and doesn't smell anymore.

I can't find the guy's # right now - it was a craigslist quickie.   He'll be cutting again this fall but meanwhile, I thought I'd ask here if anyone has a clue what it might be.    Would sitting in a tobacco barn infuse the hay with that strong a scent?  Would roundup smell strong like that?  After a month of rain in May-June it's drying out now and many of my plants are looking sad at the bottom.   Soil under the mulch is slightly moist and I've started watering.    I just hope I haven't destroyed my garden with something leaching into the soil.

Natural decomposition. The smell of tobacco I think you are referring to has to do with the curing process. Heat and humidity are forming organic ring compounds you can smell, the hay wasn't dry or has picked up moisture. Everything right now from my windrowed grass to chip mulch piles takes on that smell. It means in my opinion you have a good mix of N to C!

Either way, you are using it for mulch, just make sure it is deep enough you don't get a fescue garden out of it.

It's silage! well, of a sorts. Like TJ noted, you're smelling aromatic compounds from microbial activity. If hay is baled while still a little damp, and if it's in a low/no oxygen environment, it will sorta ferment. It usually happens in the center of unwrapped bales that are rolled/pressed real tight where a no oxygen environment develops. I've seen it in the center of big round bales and yes I also think it smells like tobacco. Some farmers do this intentionally, and the end product is called silage. They'll bale their hay while still a little damp, but not so damp it rots, and then wrap it in a cover so the entire bale is sits in a low/no oxygen environment. You may have seen them off in the fields on farms, a bunch of round bales laying end to end, then covered in a usually white wrapping. They kinda look like giant caterpillars to me.

Well that makes sense.  I was just surprised that it kind of burned my nose and throat.   This batch of fescue is decomposing faster than the mixed grass from last two years that had been stored in a barn for several months.   And I don't mind a little extra "biomass" growing along the edges - I just chop and drop or the chickens scuff it up for me.  Thanks for reassuring me :)

One other awesome thing about silage is the microorganisms it brings to the party, great stuff to use as mulch.