The answer to this depends on a few things:

• Are you preparing to harvest or to bale the hay?
• What kind of baler are you using (large square, small square, round)?
• How will your hay be stored?

Balers that compact hay tightly, such as the large square and round balers, tend to require drier hay, while balers that don’t compress hay so much can usually take a bit more moisture.

The exact amount may vary, but recommendations from some organizations, such as Alberta Agriculture and Forestry, put safe baling moisture ranges for a dense, 1800-lb. bale at 12-16% moisture content, and small, 60-lb. bales at 18-20% moisture content.

Outside of these %MC ranges, farmers risk either compromising the nutritional value of their hay, or even risking spontaneous combustion.