Take the reading from the core of several bales, with the instrument's own calibration stated, and treat a disagreement between two instruments as information rather than as noise.
How to take a hay moisture reading you can act on
window HAY WINDOWchecked 2026-09-16responsible Windrow Field Manual (a named masthead, not a person)
What you need A probe-type moisture meter, or a capacitance meter plus a moisture tester; a bale or a windrow; a notebook. Nothing else is required.
[['Probe, resistance type', 'Resistance between electrodes in the sample', 'Core moisture of a bale or a windrow'], ['Capacitance meter', 'Dielectric properties of the material against the plate', 'A quick relative reading on a windrow'], ['Oven or microwave test', 'Mass lost on drying — the reference method', 'Calibrating the other two']]
| p | r | o | b | e | c | a | r | d | : | w | h | a | t | e | a | c | h | i | n | s | t | r | u | m | e | n | t | m | e | a | s | u | r | e | s | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| I | n | s | t | r | u | m | e | n | t | |||||||||||||||||||||||||||||||
| W | h | a | t | i | t | m | e | a | s | u | r | e | s | |||||||||||||||||||||||||||
| T | r | u | s | t | i | t | f | o | r |
Steps
- Sample from the core, not the shell. Push the probe into the centre of the bale, or into the middle of the windrow cross-section.
- Take at least five readings from different bales or different points along the row. Record each one; do not average them in your head.
- Note the instrument and its setting. A reading without the instrument named is not a measurement, it is an anecdote.
- If the highest and lowest readings differ by more than about four points, stop and find out why before you bale. A wide spread usually means an uneven row.
- Write the readings down with the date and the field. The next person to make a decision will want them.
The two-instrument disagreement
| Situation | Most likely cause | What to do |
|---|---|---|
| Probe reads lower than the meter | The meter is measuring a dry shell | Believe the probe and stop baling |
| Both read low and the bale heats anyway | The sample was taken from the wrong end | Sample again from the core, at the middle of the bale |
| Readings swing between samples | The row is uneven | Ted or rake to even it, then sample again |
| Meter reads high on every bale | The meter needs calibrating against a dried sample | Calibrate before the next field |
What the number is for
The reading exists to answer one question: is this bale safe in the storage I have? That question has a different answer for a small square bale in a barn and a large round bale in a stack, so the target number moves with the storage, not with the crop.
The manual disagrees with the common advice to bale at the top of the safe band and rely on a preservative. A preservative applied unevenly is worse than a slightly later baling date, because it produces a bale with dry pockets and wet pockets, and the wet pocket is the one that heats.
Where the numbers come from
- S1Hay Moisture Testing (FSA-3065), University of Arkansas System Division of Agriculturesupports the sampling and testing procedure for hay moisture
- S2Hay Storage and Moisture, Michigan State University Extensionsupports the storage-moisture relationship the reading is checked against
- S3Propionic Acid Preservatives for Hay, University of Wisconsin-Madison Crops and Soilssupports the preservative option that is sometimes used instead of waiting
One link, one document. No home pages, no search results, no bare domains.
Put this page down Put this page down when you have five readings written down and know which one governs.