The spontaneous combustion of hay discussion has not covered all
aspects. The following is the part which relates to moist hay and
fire in a book I am writing.
DRAFT
Hay
Mould
Don't bale moist hay. Ideally hay should be at 86% dry matter (DM).
To measure the dry matter content take a large handful of the wettest
hay and weigh it by drying it in an oven or microwave (using several
small heatings) until it just about stops losing weight. Then weigh
it and divide the dried weight by the original weight (say 90 divided
by 120 = 75% DM ).
Dampness and heat cause mould and a loss of nutritional value and can
burn barns or stacks. I was told of a US farmer who always bought hay
or haylage and had hardly any live calves born for two years because
of mould affecting the cows.
Using mouldy hay for bedding can cause mould allergies, be toxic to
animals and affect their health and decrease production without your
realising it. Working with even slightly mouldy hay can affect
health, causing coughs, respiratory problems and even severe lung
damage (farmer's lung).
Stacking damp hay on pallets allows air to enter and rise through the
hay, especially if small bales are stacked with gaps and with the cut
sides up.
Good material well conserved doesn't need a preservative, however,
mould inhibitors help make better quality hay when conditions are not
perfect and can be a good investment, rather than having done all the
work, and ending up with poor quality hay which can be a liability,
rather than an asset.
In New Zealand the handling of hay is seldom a toxic risk because
barns are usually open and feeding is on pastures not in barns.
Storing Hay
In areas which have wet autumns and winters, it is important to store
hay in a barn or under a cover to avoid waste. Covers must be held
down with ample twine and weights such as tyres, or with netting. In
dry winter areas it may not be necessary to put hay under cover, or
even to bale it. In low rainfall and low wind areas the hay can be
raked into large windrows and strip grazed in winter. Bales can be
left and fed as the paddock is strip grazed.
If hay is stacked when damp with a dry matter (DM) level of 85% it
can heat and at about 75% or even lower in some cases, there is a
risk of spontaneous combustion making it catch fire and if not, mould
will develop which will lower its feed value and can cause severe
human and animal health problems.
In practise there can be areas of a paddock where the hay is not as
dry as it should be. These can be sheltered areas, the corners or in
the shade of hedges or trees. The wet bales should be left spread out
in the barn or kept out of the stack and spread out to dry. If rain
is likely cover them as best you can. If there are a lot stack and
cover them then unstack them to dry after the rain stops.
Slightly damp small bales baled and stacked loosely to allow air to
circulate can help it dry and reduce the risk of fire, but not
eliminate mould. With large bales stacking loosely is not practical
or helpful because there is so much in the bale which can heat and go
mouldy.
There are mould inhibitors which can be added at baling. Use only
ones which don't corrode the baler, but they or salt won't save the
hay from burning if the DM is under 70%.
If you have to bale moist hay, then loosen the adjustments to make
the bales less compact.
Regarding temperatures, heating hay will smell and steam may rise
from it, so open it up, turn the bales, spread them around,
immediately, but be careful of combustion.
If fire is imminent phone the fire brigade and never walk on the hay.
It could be ready to ignite which needs air. Not much can burn
without air. Disturbing smouldering hay can let air in and woosh, so
be careful.
On top of that heating hay can give of highly toxic fumes.
All the above gives the message that planing is essential. Don't mow
if rain is likely. Mow with a lacerator and turn frequently to halve
the drying time. If rain occurs unexpectedly you'll get some warning
so make vacuum silage or balage before rain falls. Material which is
too dry for silage and gets wet will still make reasonable vacuum
silage.
Use contractors if necessary and possible. Both are packed tightly so
exclude the air, but if either are too dry they can still go mouldy
and be dangerous to feed.
It is not only moist hay which can combust; dry silage, damp leaves,
oily rags, coal and even bodies can burn without a match.
Specific information on heating, fire and temperatures can be seen on
- http://www.montana.edu/wwwpb/ag/hayfire.html
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Best wishes,
Vaughan Jones
