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

“Murphy’s Law says that Once you’ve baled your hay it will rain!” says Frank Mickan, Pasture and Fodder Conservation Specialist, NRE, Ellinbank. Many farmers are starting to realise the benefits of feeding or selling higher quality hay in recent years because they have learnt that higher quality means more meat or milk production. As a result some farmers are risking making slightly earlier hay and so increasing the risk of meeting rain head on! However earlier hay making can be greatly assisted by utilising mower conditioners and tedders.

Unfortunately the higher the quality is the hay, the higher the losses when bales become wet from rain. This higher quality is due to the higher amount energy (eg. water soluble carbohydrates) and protein in the plant. When hay becomes wet plant respiration, leaching, and possibly mould, microbial and yeast growth later on, all result in dry matter and quality losses. So rain damage is to be avoided or minimised as much as possible

Following are some considerations which may be of assistance to you.

If rain is on the way and you won’t have all the bales under cover (shedded or tarped) before it arrives, what can you do?

Stack small square bales into a triangular stook using 3 bales on edge. Farmers often make stooks using two techniques.

  1. Stand the bales on their ends in threes so that they resemble an “indian teepee”.
  2. Lay two bales horizontally on their edge so that they lean into each other at the top edge. This will form a “V” into which the third bale is then placed. The uncut side of the bales should be facing up since it tends to shed the water more effectively. The second technique is the better method for shedding rain off small square bales.

Large square bales can be stacked in small stacks around the paddock, but it is preferable to cover them with tarps or plastic sheets.Although the outer edges of the bales will become wet, their internals should remain relatively dry, unless the rain is gentle and of a long duration. A heavy down pour is far less damaging than a persistent drizzle.

Round bales, if baled tight, or net tied, will shed much of the rain. To avoid the high losses mentioned above round bales of high quality material should be shedded as soon as possible, or stacked and covered with plastic to minimise losses. A 6¢x 5¢bale (2m X 1.6m) contains over 50% of its weight in the outside 300 mm,  so reducing wastage of round bales stored outside is essential.

What happens after the rain?

When the rain passes, if the forecast is for some fine weather (2-3 days), you may wish to leave the bales in stooks so that any breeze will increase the rate of drying. If there is likely to be only a short period (about 0.5-1 day) pull apart the stacks of small square bales to allow the outside bales to continue drying. Cart the dry internal bales into the shed. Make sure the bales are completely dry. A small section of one bale containing moisture may be adequate to cause spontaneous combustion ie catch fire, if shedded before becoming sufficiently dry. The wet bales may be carted in last if reasonably dry, but should be stacked to allow air to move through, around, and over the top of the stack to allow any heat generated by wet bales to escape and prevent needless heat build up. Alternatively and preferably, if shed space permits, use this larger area to stack the wettest bales with plenty of spacing..

Large square bales will heat substantially if baled too wet, much less being rained upon from a great height once baled. Their larger denser nature of these bales do not allow them to “breathe” and will heat substantially. This greatly increases the risk of fire compared to small square or round bales.

If not sufficiently dry when carting in to the shed, and no extra area is available to spread them out, place an object such as sleepers or tyres between layers to allow the heat to escape.

It is particularly hard to guage the internal dryness of wet round bales which have been left standing in the field for several weeks so be ultra careful if they are shedded. Bales tied using netting will shed rain much more effectively than string tied bales, reducing dry matter losses by about 10% for bales left outside.

Note that bales left in damp paddocks, in puddles, or affected by floods, are potential “fire starters”.

All bales which are rain affected will be much damper than normal, even after a period of drying, so regularly monitor the stack for signs of dangerous heating, and do so for up to seven weeks.

Many farmers in the past have spread salt between the layers of hay to absorb the moisture.  Research into this practice indicates that it is not a viable option to reduce moisture or the prospect of mould/fire damage. A very large amount of salt is required to have any affect and this may cause problems if too much is consumed by cattle when fed out. The layer of salt may aid in absorbing some of the moisture at the junction between the layers, but won’t have a great affect within the bales. It is the moisture deeper in the bales which causes the problems.