Getting hay baled at the correct moisture can be difficult to accomplish, especially when it is cloudy or we have high humidity.

Hay moisture testers are electronic gadgets that you poke into either a bale or a windrow and the device is supposed to tell you the moisture content of the hay. I say supposed to tell you because it can be very risky to blindly believe values displayed by the tester. This doesn’t mean that hay testers can’t be trusted. It means that you as the operator need to know more about how the tester works, what causes values to vary, and how to use the tester most effectively.

Hay moisture testers actually measure the electrical resistance of the hay between two sensors. The more moisture, the less resistance. Then they convert this resistance to a value associated with average moisture content.

However, other hay characteristics influence how testers sense moisture. For example, tight or dense bales, or even areas within a bale, will give different results than looser hay. Wiggling the probe or inserting it at an angle versus straight into the bale changes the value. And hay with dew moisture gives much different values than hay without dew even when overall moisture content is the same. While this sounds like testers can’t be trusted, they can help if you take the time to use them for a while and learn what readings and what conditions indicate when to bale and when not to bale.

With that experience with your hay and your moisture tester, you then can interpret readings accurately and get the guidance you need.