Spontaneous combustion has caused a spate of haystack fires across SA in a year when replacing fodder will be a major challenge.
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Feedworks ruminant nutritionist Ian Sawyer says high moisture levels in hay trigger many fires, but in dry years such as this it is more likely to be microbial activity fed by the massive levels of water-soluble carbohydrates remaining in plant tissue.
In normal years plant nutrients are transferred to the seed head but in drought years the failed crop may undergo senescence leaving the sugars stored in the stem.
The heat which causes the fire is a result of oxidation of these plant nutrients by fungi, mould and yeast.
Hay in these years can be up to 25 to 30 per cent water-soluble carbohydrates – twice the levels of a normal year.
“People think hay fires are an act of God but they are an act of microbes and the right conditions to assist them to do their work,” he said.
“In 2008 we showed it was better not to chase the last few per cent from 15-12pc (moisture) if you are going to set up more microbial action by having hay on the ground for longer.”
Mr Sawyer encouraged those concerned about their stored hay to get a feed test, which included water or ethanol soluble carbohydrate levels to understand their risk. In years such as this WSC levels can vary from 15pc up to 25-30pc.
“And if you know your hay was down for two weeks I can almost guarantee whether it was tedded or in a windrow they will be a reasonable bug load in it.”
Producers at high risk should consider making smaller stacks and all producers should check to ensure their hayshed roof is watertight. Spontaneous combustion can take place 4-14 weeks after baling but can also occur later in the season on some occasions.
