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A Guide to Hay Bale Harvesting When Wet

Bale harvesting after rainy weather

As a hay farmer in the British Isles, you know moisture is your sworn enemy come bale harvesting season. With these practical tips, you can bale nutrient-rich, quality hay even when Mother Nature blessed you with wet hay bales.

What to do with wet hay

After cutting, the hay crop is left to dry to about 15% moisture before it is baled. Rainfall can negatively impact hay quality. This depends on a few factors:

  • If rain falls shortly after cutting the hay before it has had much time to dry out, the hay may still be okay.
  • Windrows will likely shed light rain (less than half an inch) without much damage.
  • Intense, heavy rainfall is better than a light, extended drizzle.
  • If rain re-wets the hay only once, versus multiple times, damage is less likely.
Tips for baling wet hay

If the hay was nearly dry, use a hay preservative or inoculant if the moisture content is still less than 30%. However, excessively wet hay bales risk growing mould that generates heat, creating a fire hazard (see below). Consider making baled silage although this may not be possible depending on time since cutting the grass – see above.

Don’t stack wet bales immediately – spread them out to cool. If your baler allows, make smaller bales which have a larger surface area relative to their volume. This allows for faster cooling than in larger bales.

...make smaller bales which have a larger surface area relative to their volume....
The risks of wet hay bales

When hay is baled with high moisture content, it can lead to problems like hay spoilage, fires – from self-combustion, and reduced nutritional value. This is because of a process called ‘heating’.

After cutting hay, the crop continues to respire (breathe) and heats up.  This can cause toxic microbes to grow. If wet hay is baled, microbes will multiply rapidly which increase the heating process. To prevent this, cut hay needs to dry to slow down respiration. Tedding (fluffing) wet hay can speed up drying but may cause excessive leaf loss in leaf crops.

The safe moisture level in hay crops for baling depends on the bale size and type of hay crop. Small square bales should have 15-22% moisture to minimise leaf loss, moulding and heating. Larger round or large square bales, being more dense, should not exceed 18% moisture as they retain internal moisture and heat longer. If baling large bales with crops above 22% moisture, don’t stack them for at least 30 days.

Tips for protecting your hay with net wrap

It’s important to wrap wet hay bales as soon as possible after baling to prevent nutrient loss from exposure to moisture. Use enough layers of net wrap to ensure edge-to-edge coverage. You can find out more about how many layers to use and the choices of net wrap Tama offers here.

For more guidance when facing the risk of wet hay bales, get in touch with Tama Assist.



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