If other people are having some of the same issues our farm has with this wet weather, you’re probably nearing the end of your hay reserves and chomping at the bit waiting for dryer weather to start first cutting. Keep in mind though that there are several hazards associated with wet hay, especially hay that has over 20% moisture for small square bales, 18% for round bales, and 16% for large squares when baled without a preservative. The best way to prevent these hazards is to make sure the hay is dry enough before you bale it, but it can be hard to avoid getting a few wet bales every now and then.
The most severe hazard is the risk of spontaneous combustion. If the hay starts decomposing, it can generate a lot of heat, and if this happens in the middle of the stack you might not notice until you have a big problem. Combustion can happen within 3 or 4 weeks of baling, and at temperatures as low as 175 degrees Fahrenheit. The other main hazard is mold, which can ruin the hay and cause health problems for people and animals. Hay that is baled when it is still too wet can also loose a lot of it’s nutritional value.
Ideally, the best prevention is to avoid baling when the hay is too wet, but anyone that has been in the hay business knows that this doesn’t always happen even when conditions are ideal. One thing that I’ve seen people do with wet hay that seems to be pretty effective is to stack the hay on pallets in an open area away from buildings and put a tarp over it to prevent it from getting wetter. Also make it part of your routine to monitor your hay for hot spots for the first month or so after you store it. If you get temps over 130, monitor it daily. If you find any spots over 145, you’re nearing the combustion point and should remove bales from the hot spot. Over 160, call the fire department because your hay is either on fire or almost on fire.
Another strategy, especially if you only have a few wet bales mixed in, is to feed the wet bales first. This prevents fires and also helps you get the most out of the hay before it gets moldy or looses nutritional value. In my experience the big squares seem to be especially prone to mold, plus if they do go bad it’s a lot of material to dispose of, so for those be very careful of your moisture levels and consider using a preservative if you don’t already.
There are also a number of strategies to optimize drying while the hay is in the field. The Wisconsin extension has a good summary of things you can do as far as width of rows and timing of raking with a lot of good graphs and data tables so I’ll share that in the link below.
I’m really hoping the weather will dry up soon so we can get some hay up without it being wet, but given the weather reviewing some strategies for preventing wet hay or dealing with it when it happens seems like a good idea. Here is a link to the original article I was reading. This article also has a link to Purdue’s comprehensive forage guide, which goes into great detail about how to prevent mold/fires and general information and planting strategies for forage crops.