THIS year is another nightmare year for hay baling in most regions. This article is aimed at farmers making small or large square bales that could be rain-affected.
Is it forecast to rain before freshly-baled hay can be put in the shed?
If yes, small square bales can be stacked into triangular stooks, using two techniques. Stand the bales on their ends in groups of four so that they resemble a teepee or an inverted ‘V’ shape.
Place another bale on its edge in the ‘V’ to help shed the rain. The uncut side of the bales should be facing up since it tends to shed the water more effectively.
The other method is to stook bales horizontally. The first two bales are laid on their edge and leant against each other so that they touch only on their top corners. The third bale is then laid on top in the ‘V’ shaped area formed by the first two bales, the uncut side facing upwards.
Large square bales can be stacked to whatever size stack is practical and safe around the paddock. If possible, they should be covered with tarps or well-tied/weighted with plastic sheets to prevent rain entering the bale surfaces and between the bales themselves.
The latter is a good spot for spontaneous combustion to occur. Some farmers stand large squares on their end which is recommended for shedding much rain, and subsequently drying out faster.
Remember, the protective sheet should only be a temporary fix as the bales will generally need to continue to cure, especially if baled slightly on the wet side. Even hay baled at the correct moisture content will still cure down to reach an equilibrium moisture content of about
15 per cent moisture.
The moisture given off in this process causes the ‘sweating’ of hay.
Once you’re sure the rain has passed, remove the cover to allow this moisture to escape and prevent it building up under the sheet.
Although the outer edges of the stack will get wet, their internals should remain relatively dry, unless the rain is gentle and persistent. A heavy downpour is far less damaging than a long drizzle.
If a light shower is expected, the increased density of the large squares will prevent excessive water ingress and it may be possible to leave them where they lie.
Round bales, if tightly baled and netwrapped, will shed much of the rain.
They shed rain more effectively than string tied bales, reducing dry matter losses by about 10 per cent. Bales made early in the season will have a high digestibility due to their leafiness and high sugar content.
If rained on, dry matter and quality losses can be severe.
They should be shedded as soon as possible or stacked and covered with plastic to prevent large losses.
Over 50 per cent of the weight of a two metre diameter round bale of hay is in the outer 30cm, so anything to reduce wastage of round bales stored outside will be very
beneficial. Stacking them tightly end to end will protect the vulnerable flat ends of the bales.
What to do after the hay bales have become wet?
Pull the square bale stacks apart to allow the outside bales to start drying. Cart the dry internal bales into the shed, ensuring the bales are completely dry. Moisture in a small section of one bale may be enough to ‘fire up’ a stack if not dry enough. Depending on where they
are wet, bales may require flipping for a few hours drying before shedding. This is easier said than done in a La Niña year!
If bales are still damp on shedding, they should be stacked to allow air to move through, around and over the top of the stack. These bales will sweat and heat.
Encouraging air circulation will allow the heat and moist air to escape. Or, if space permits, stack the wettest
bales over the largest area possible. If you do not have sufficient area undercover to spread them out, and if you must stack them, try to place something like 4 x 2’s or sleepers between layers to let heat escape.
If the weather turns hot, leave the wetter bales outside to dry, but if the weather looks bad, put the wetter bales on top of the dry shedded bales. However, it would be preferable to spread these in another bay or shed until they are sufficiently dry.
If large squares are baled too wet, their larger, denser nature doesn’t allow them to breathe and they will heat substantially even without added moisture from rain.
This will occur if baled at over 16-18 per cent moisture content, and ideally, should be baled at less than 14 per cent moisture. This is why most hay fires occur in large square bale stacks.
It is particularly hard to gauge the internal dryness of wet round bales which have been left in the paddock for several weeks, so be very careful if you shed them.
All bales in the above situations will be much damper than desirable, even after a drying period, so watch the shedded stack for several weeks for signs of dangerous heating.
Be aware that bales sitting on damp paddocks, in puddles, or caught in rivulets of water or floods, are also a potential cause of spontaneous combustion.
