Hay Moisture Meters

A hay moisture meter is a specialised device used to measure the moisture content of hay bales, helping farmers and livestock owners prevent spoilage, mould growth, and fire hazards caused by excessive moisture.

It typically features a long probe that is inserted into the bale, with a digital or analogue display showing the moisture percentage.

Accurate moisture readings ensure hay is stored safely and maintains its nutritional value, making the meter an essential tool for proper hay management.

For large square bales, aim for below 18% before baling. Dense bales hold heat far longer than small conventional bales, so the risk of heating, mould and, in serious cases, spontaneous combustion rises sharply above that threshold.

Small square bales have more tolerance and are generally safe up to 20-22%, though 18% is still the sensible target. Hay baled above 20% will almost certainly develop some degree of mould, and even hay baled in the 15-20% range will sweat as microbial activity continues after baling. A rough rule of thumb: expect around 1% dry matter loss for every 1% of moisture that dries down once the bale is made.

Please note these are general guidelines. Your target will depend on bale type, crop variety, storage conditions and local humidity. Check with your agronomist for specific recommendations.

For large square bales, probably not without careful management. Heating and mould are likely at that level, and spontaneous combustion is a real risk.

If you have no choice but to bale at 20%, do not stack large bales for at least 30 days, keep air circulating around the stack, and check temperatures regularly with a probe thermometer.

Small square bales handle 20% better, though you will still see dry matter loss and some reduction in feed quality as the bale heats.

If you are regularly forced to bale above 18% due to weather, a hay preservative applied at baling can reduce the risk, but it is not a substitute for monitoring moisture properly in the first place.

Yes, given enough time, good air movement and some sun. At 70% humidity drying slows significantly, and above 90% hay will not reliably dry below 20% moisture whatever the temperature is doing.

This matters in the UK because ambient humidity is frequently above 70%, especially overnight and in the early morning. Weather forecasts give you a regional picture, but conditions in the field can be wetter than the forecast suggests.

Many contractors find the most reliable approach is to bale later in the morning after the dew has lifted, using a meter to confirm the crop is ready rather than going by feel or appearance alone.