After recent rainfall in the region, some potentially high quality hay which was on the ground might now be rain-affected, reducing dry matter yields and nutritive value while increasing the difficulty of getting the hay to the desired dry matter percentage.
The problem that comes with rain during harvest is the potential for baling material to be two to five per cent higher in moisture content than it should be for the particular bale form.
Large rectangular bales need to be about two per cent drier (12 to 14 per cent moisture) than large rounds (14 to 16 per cent) which themselves need to be about two per cent drier than the small squares (16 to 18 per cent). This is due to the high density or large volume to surface area for the large rectangular and round bales, respectively.
Leaving wide windrows behind a mower-conditioner, tedding immediately after mowing (tedders will substantially speed up curing), and using a form of hay preservative are all essential tools to increase the curing rate of hay.
If these are not done, some hay may end up in a stack that has not been cured sufficiently — and unfortunately this presents the possibility of mouldy hay which can increase the risk of spontaneous combustion.
Regularly monitoring the stack from week one after baling for signs of heating is important.
Some of the signs to look for include:
■Heating of bales;
■Dampness on the tops of bales;
■Steam rising from the stack;
■Unusual odours (such as pipe tobacco, caramel, burning, musty smells);
■Moisture build-up on roofing iron or under a tarped outside stack;
■Corrosion on underside of tin roof; and,
■Sometimes the stack may slump in places.
Unfortunately, much of the heating will occur in the stack centre which is difficult to detect.
To try to get a handle on how hot the stack has become, push a crowbar into the stack as far as possible. After a couple of hours it can be removed and felt for how hot it is.
A rough guideline to the bar’s indication of stack temperature is:
■Cooler than 50°C — can handle bar without discomfort. Check temperature daily.
■50°C to 60°C — can handle bar for a short time. Check temperature twice daily. Remove equipment from shed.
■60°C to 70°C — can touch bar only briefly. Check temperature every two hours. Move hay from top layers to improve air flow.
■ Hotter than 70°C — bar too hot to hold. Significant potential for fire. Avoid walking on top of stack. Call the CFA.
To measure temperatures further into the stack centre, use a steel pipe (3m long) of about 20mm diameter. Drill eight to 10 holes (4mm to 5mm diameter) about 75mm from the end, which has been flattened to allow the pipe to be pushed into the stack.
— Agriculture Victoria senior dairy extension officer Frank Mickan