What is your baled silage telling you after months of storage?
Continued from January 2012 MML
Frank Mickan, DEPI Ellinbank
An article in last months MML highlighted three of five reasons for failed silage. This edition will cover reasons four and five:
- Incorrect dry matter content at baling (Previous issue)
- Wrapping/sealing problems (Previous issue)
- Damage to the plastic seal (Previous issue)
- Quality of the plastic film
4. Plastic film quality
The quality of film varies between companies and sometimes even between manufacturing runs. Most plastic film is manufactured to a thickness of about 25 micron, although some are now manufactured a bit thicker or thinner. These films are thin compared to sheet plastic (25 cp 100 – 200 micron), so those produced with less than desirable quality control can vary substantially in thickness.
Ultra-violet (UV) light inhibitors prolong the period of time before solar radiation begins to break down the plastic. The degradation of the film from UV radiation can be recognised when it starts to split, or the edges lift up and rip easily when pulled instead of stretching (see Figure 1).
Figure 1: Film breakdown due to solar radiation
Some European countries use negligible or low rates of UV inhibitor in their film because they do not experience the great intensity of solar radiation that Australia does, and therefore have little problem with film breakdown. Australian conditions demand the highest level of protection for our climate, however after the UK and European harvest is completed the excess film is often exported to Australia for our harvest. Some of these films are of the highest quality, some are not.
The quality of the resin used to make the film and the level and quality of the UV inhibitors to protect the film from solar radiation breakdown can also vary considerably worldwide. The world pricing of fuel impacts on the price of resin, so savings measures (short cuts by using poorer quality resin) are sometimes taken. The old adage that you generally "get what you pay for" is foremost in the silage film market.
Solution: Use films from reputable manufacturers and those who are prepared to at least discuss any problems which may arise, many of which are often not caused by the film itself.
There are many causes of holes in baled silage wrap; birds, vermin, wildlife, cattle, domestic pets, children, tree branches, etc can all cause holes in films. The grain in whole crop cereal silage baled at the soft dough stage is a beacon to vermin for example.
Solution: Try to control pests as much as possible. Where possible place the bales on sand or bare soil. Leave gaps between bale rows to allow for easier inspection and repair. Put baits in place before any vermin start to appear. Place hay net wrap along the tops of bales, preferably on top of tyres, as birds hate to have their claws entangled. String humming wire over the tops of bales and thread through the handles of plastic drums half filled with water. Always ensure fences are stock proof.