The subject of bales of hay came up on an email list I recently joined. The question was time sensitive, as in, were there bales of hay during such and such year. This got me thinking so I did a quick search and discovered that the Hay Press was invented before the Baler. Or should I say the use of the term. A hay press was the term of the time, a hay baler didn't really come into vogue until 1930's or so.
Hay Presses came into use in the mid 19th century, around 1850's. However, they did not become popular for the every day farmer until 1870. Before the invention of the press, hay was into hay stacks around the farm.
Here's a link to a patent for a hay press 1880 Click the small images on the page to see the details.
Here's a picture of a horse powered hay press
And another image of a man powered hay press
By the end of the 19th century Hay presses became much more common. So, if you're writing about farm life in the 19th century keep in mind the technology that was available, when it was invented and how soon before it became popular in use.