A tedder lifts the crop, breaks the mat, and drops it back fluffed. It buys drying hours only inside a narrow moisture window, and outside that window it costs you leaf.
Tedder: the machine that fluffs a swath
window HAY WINDOWchecked 2026-09-16responsible Windrow Field Manual (a named masthead, not a person)
[['Crop above 60% moisture', 'Drying is surface-limited', 'Ted. The gain is large and leaf loss is small'], ['Crop 40–60% moisture', 'The window where tedding pays', 'Ted once, in the morning, before the dew lifts'], ['Crop below 40% moisture', 'Leaf shatter starts to dominate', 'Do not ted. Rake and bale instead']]
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What the machine actually changes
A tedder does not dry hay. It rearranges it so that air can reach more of the surface and so that the mat of stems, which holds water against itself, is broken up. Every drying gain from tedding is a gain in exposed surface, and the arithmetic is the same arithmetic as swath width.
| Tedder type | Action on the crop | Best used when |
|---|---|---|
| Rotary, upward-throw | Lifts and drops the crop, breaking the mat | The crop is heavy and lying flat |
| Rotary, rear-discharge | Fluffs in place, less scatter | The crop is light and already lifted |
| Tedder-rake combination | One pass teds, a later pass rakes | Labour is the binding constraint |
The moisture window, and why it is narrow
Above roughly 60% moisture the crop is wet enough that leaves bend rather than snap, so the leaf cost of one pass is small and the drying gain is large. Below roughly 40% the leaves are brittle and the drying gain has shrunk, because what is left to lose is stem moisture and the stem is the slow part. Between 40% and 60% is the band where one pass reliably pays.
The band is a rule of thumb from field observation, not a law. The peer-reviewed drying models put the leaf-loss onset at a moisture that depends on the species and on how long the crop has been lying.
Boundary: tedding is not raking and not merging
Tedding disturbs the swath in place. Raking moves it sideways into a windrow. Merging combines two rows. These three operations are often described as one handling pass in the trade press, and treating them as one is how leaf loss is under-counted: each pass has its own cost and they add.
The misreading worth naming: a tedder set too aggressive throws the crop over the mown width and leaves a thin, uneven row that the baler cannot pick up cleanly. The drying looked good and the baling loss went up.
Where the manual argues with the dealer literature
Equipment literature presents tedding as a tool with a setting, and implies the setting solves the problem. The manual holds that the decision is the moisture window, not the setting. A perfectly set tedder used at 22% moisture is a machine for converting hay into leaf meal.
Where the numbers come from
- S1Hay Making, Penn State Extensionsupports the role tedding plays in the harvest sequence
- S2Modelling the field drying of hay, The Journal of Agricultural Science, Cambridge University Presssupports the modelled drying behaviour that makes surface exposure the limiting factor
- S3Big Bale Storage Losses: How Different Options Stack Up, University of Wisconsin-Madison Crops and Soilssupports the handling-loss figures used when the crop is moved dry
One link, one document. No home pages, no search results, no bare domains.
Put this page down Put this page down when you know today's crop moisture. Without that number the tedder decision is a guess with a diesel cost attached.