Guide to Moisture Content of Hay

Frank Mickan is the Pasture and Fodder Conservation Specialist with the Department Environment and Primary Industries (DEPI) at Elinbank in Victoria. 

Heating is most likely to damage hay stored at moistures above 30%.  Minimum changes occur if it is baled at 20% or less although if it is uniformly dry it can be baled and stored safely at 25%.  The 25% level is the average moisture in curing hay at which it is dry enough overall to avoid moulding or hot spots that occur with variations in moisture content that are usually at higher average moisture.  Large square bales need to be baled at a lower moisture content than small square or round bales.

Frank Mickan, Pasture Specialist at NRE Ellinbank, says to test the hay for moisture right through the windrow and test in several spots across the paddock.

He says hay moisture can be very variable in an uneven or wet crop or if it has not been handled well.  It is not good judging moisture content from a single sample of drying hay.

The following is a guide to the moisture content of the hay crop as it is drying:

  • 30 to 40% - leaves begin to rustle.  They do no give up moisture unless rubbed hard. Moisture easily shows in stems scratched with a fingernail or, not so easily, when twisted in the hands.
  • 25 to 30% - the hay rustles.  A bundle twisted in the hands will snap with difficulty; it will show no surplus moisture.  Thick stems may show moisture if scraped or split open with a fingernail.
  • 20 to 25% - the hay rustles readily.  A bundle will snap easily if twisted; leaves may shatter and there are few moist stems.  Nodes or joints are shrivelled and the bark on the stems cannot be lifted with a fingernail.
  • 15 to 20% - the hay factures easily. Bundles snap easily when twisted.  It is difficult to see any moisture and the leaves shatter readily.

Remember – make a few test bales: a few trial bales will give the final answer to your question of: When should I bale?

You are baling too soon if – the crop wraps on moving parts of the baler; the baler engine labours unduly; the bales are too heavy; the hay bale lacks spring; there is a smear of moisture on the side of the bale.

You are baling too late if – the hay shatters; the hay is dusty; there are too many leaf fragments; the bales are too loose and light, even after tightening the bale chamber.

Finally, if the crop is too dry, say 12 to 15% moisture content, you may have to wait for the evening dew to bring the crop back up to 18 to 20% moisture content.