September 2010 edition
Frequently asked questions about silage
Frank Mickan, Fodder and Pasture Specialist, DPI, Ellinbank
Many questions are asked every year about making and storing silage. Following are answers to some of the more common questions but bear in mind that there are often many factors to be taken into account when answering silage related questions.
What is the correct DM content for each form of silage?
Stack silage: Long chop silage (loader wagon) 30–35% DM. Precision chop silage 30–40% DM.
Baled silage: Round bales 40 – 50% DM. Large rectangular bales 45 – 60% DM.
How can I tell if the forage is too wet to ensile?
Stack silage: If moisture drips/runs from a handful of forage (chopped into 2 – 3 cm lengths) and squeezed for about one minute, it’s way too wet. Moisture oozing out of a silage cart during transport or from the stack during rolling. Slight dampness on rolling tractor wheels indicates correct DM content.
Baled silage: Tractor blowing exhaust smoke. Baler has trouble turning in chamber. Bale ends blackened during baling. Perimeter of bale glistens in sunlight due to moisture on the bale exterior. Bales (1.2 m x 1.2 m) are almost impossible to stand on their ends by one man.
If my silage is not wilted enough, and rain is coming, can I still ensile it?
Yes, but to ensure a good fermentation (pleasant, sweet smelling silage), apply an inoculant (or other appropriate silage additive) from reputable companies. Apply at the recommended rate per tonne fresh weight acknowledging extra cost due to extra weight of the water.
If my hay is not quite dry enough, and rain is coming, can I make silage out of it?
If the crop has been on the ground for many days (eg. 4+ days) and/or has been severely affected by rain, the crop will be probably depleted in plant sugars, essential for ensiling. Wrapping may/may not allow a crop to be salvaged as high DM silage. Applying a buffered acid silage additive (or other appropriate silage additive) at baling may assist the fermentation process. Applying an ordinary silage inoculant probably won’t assist due to lack of sugars, their food. Baling as hay using a hay preservative and not wrapping is now an option with these preservatives becoming available.
How do I know if the stack is rolled enough?
The forage will not be depressed by the rear wheels more than a few centimetres as they pass over the stack. Rolling slowly rather than quickly aids compaction. Fingers can be pushed into only the first joints into an opened stack face.
How do I know if the bales are baled tightly enough?
Bales should hold their shape some time after baling when left on their round side. Fingers can only be pushed into the first joints into the ends of bales.
Should I cover the stack during harvest?
Ideally, yes. The rolled stack will contain a certain amount of air, no matter how tightly compacted, allowing plant respiration and microbial bacteria activity to occur, resulting in DM and quality losses. Carbon dioxide + water + heat are given off and rises as hot air! This heated air rises out of the stack to be replaced by cool air. A plastic sheet dragged over the stack and with tyres placed around its perimeter, will greatly slow down this cycle.
When should I cover the silage stack after harvesting is finished?
As soon as rolling is completed. Cover with plastic and place weight such as tyres, sand bags or dirt over the entire stack surface and seal edges airtight.
Are there alternatives to using tyres for sealing and weighting plastic sheets?
Ideal: A thin layer (3 – 5 cm) of soil over the plastic over the entire stack surface and 5 – 10 cm over the plastic edges. Painful to remove soil but consider throwing some grass seed on top to act as handles to easily remove soil at feed out.
Make “sausages” containing dirt, sand, pea gravel, etc. out of last year’s sheet plastic (Figure 1) and lay in overlapping rows along plastic edges, at overlaps and in rows across the stack surface.
Right - Figure 1. “Sausages” made out of old plastic and hay twine
When should bales be wrapped?
Within reason, as soon as possible after baling to several hours later. Never leave them unwrapped overnight and, if unavoidable, stand bales on their butt to make wrapping possible the next morning.
How many layers of plastic on round and rectangular bales?
Four layers ALL over the bale at 55% stretch with NO underlapping. Six layers are recommended if transporting bales, if being left in paddocks on stubble or if bales are to be carried over to give two years safe storage.
When can I open my silage after it is made?
Stack silage: Silage requires at least 6 – 8 weeks for the whole stack to ferment if compacted tightly and sealed airtight within hours after harvest is completed. If material is too dry, not rolled well, only covered and not sealed, etc. fermentation will take several weeks longer. If opened earlier, the open area of the stack will be flooded with air and fermentation will be affected with loss of dry matter (DM) and nutritive value.
Baled silage: Individually wrapped bales can be opened anytime as long as the bale is consumed within the day. Fermentation won’t be complete but won’t matter. By day 2, it will be heating and starting to go mouldy. Treat large square bales under sheets of plastic as a stack and don’t open for 6 – 8 weeks.
When can I send silage samples for feed analyses?
After the above opening periods and, ideally, several weeks longer in case the fermentation is taking longer which commonly occurs. The results will be incorrect if sent earlier.
How much silage is in my stack?
This will depend on silage DM content, cut length, stack depth and how well the stack was compacted. Table 1 shows the silage densities of 168 silos in America, but similar densities will apply in Australia.
Table 1. Approximate weight of silage per cubic metre (kg/cu.m)
Weight basis |
Pasture, Lucerne |
Maize |
|---|---|---|
|
Density (kg/cubic metre) |
||
|
Average (Range) |
Average (Range) |
|
|
Fresh weight basis |
590 (210 – 980) |
690 (370 – 960) |
|
Dry weight basis |
240 (110 – 430) |
232 (125 – 378) |
