I had gotten a load of bad hay this year. Before I realized there was no way my horses would eat it I kept trying different bales figuring maybe a dog peed on the bale. This left me with a bunch of wasted hay in winter making getting rid of it difficult. I tossed it along a bank near my barn. Which begs the question will this mulch down on its own or should I do something to it. At the bottom of the bank is a stream so I don't know how safe using lime due to run off to the stream. Id say there is 10 bales of hay broken and spread out as best I could.
Yes, lay down hay thick enough and very little will grow through until it starts to break down.
Finding bad hay when you anticipated good is almost tear worthy, even just a few bales, but bad hay has lots of value too.
Goats or cattle as DB suggested. I loff it for speeding up the composting of my manure piles, and keeping them tidy and from looking like a hill o' crap, I blanket each pile in old hay.
If you want to kill off growth in an area you can spread it down thick. I love it in the garden, especially container gardening, I put a thick wad of old hay at the bottom of my smart pots. It helps wick up moisture from the ground and keep the pots from drying out. I also use bad hay as a mulch where I don't want weeds to grow, but I have to mulch over that as by the end of the growing season I'll have a carpet of grass from the hay seeds instead.
And thats the final use I love, if its a seedy cutting, I spread it in the pastures where the grass is sparse or there is little or no thatch, to spread seeds and leave some organic material to help hold moisture.
Worry is the biggest enemy of the present. It steals your joy and keeps you very busy doing absolutely nothing at all... it’s like using your imagination to create things you don’t want.