Hay? Why Hay? Well it was a part of everyday life back in the 19th century. I know that title for this post sounds a bit confusing but this comes from an 1810 publication "The New Family Receipt Book." The actual title of this paragraph is "To Prevent Hay-Stacks from taking Fire." Which baffles me in reading the actual paragraph but some of you are more knowledgeable than I in this and can share why that title.
When there is any reason to fear that the hay, which is intended to be housed or stacked, is not sufficiently dry, it is only necessary to scatter a few handfuls of common salt (muriate of soda) between each layer. It would be very ill judged to regret this trifling expense; for the salt, by absorbing the humidity of the hay, not only prevents the fermentation and consequent inflammation of it, but it also adds a taste of this forage, which stimulates the appetites of cattle, assists their digestion, and preserves them from many diseases.
So I did some further searching about hay bales burning in farmer's fields today. Apparently this happened in Spring when green bales of hay can produce an interior heat and combust on their own. Which is why we see all these random bales of hay in the farmer's fields. So, if they do combust the bale will only burn a single bale. I also read on a homesteading board that a handful of salt is used between bales of hay. Another writer wrote "The salt absorbs the moisture, and helps so the hay doesn't heat up if put away with too much moisture." Which says to me that green hay can and will ignite, which explains the 1810 title. Don't you just love research?