Silage fermentation does not begin until the forage in the stack or bunker is under oxygen-free conditions. Compaction removes air from the forage and sealing keeps it out. There are several key steps to achieving a good seal on your stack or bunker:



  • Smooth the surface. This allows the cover to be laid flat without any creases or folds
  • Apply salt. Some farmers choose to apply 1-2 kg of agricultural salt per square metre to the surface of the stack or bunker before covering. This eliminates any spoilage of maize silage immediately under the cover. This should be considered as an optional step.
  • Cover quickly. Ideally the stack should be covered and sealed immediately after harvest as this will speed the fermentation process and reduce losses. Consider safety aspects (e.g. power lines, the risk of falling off the top) especially when the weather is windy.
  • Tape holes and joins. When taping joins avoid a large overlap as condensation can form between the layers and drip into the silage causing spoilage.
  • Weigh the cover down. The cover needs to be held tight against the silage. You can weigh down the cover using tyres that are touching, sand bags or lime.
  • Seal the edges. Sand or limestone should be used to seal around the edges of the bunker or stack.
  • Keep stock out of the stack or bunker area.
  • Check the cover regularly. Patch any holes as soon as they develop.

Rats and Mice

Rats and mice can cause considerable damage to stored maize. As well as making holes in the cover which exposes the silage to the air causing spoilage, they also carry a number of diseases. It is much easier to keep them out of silage stacks and bunkers than to control them once they are in the silage.

To keep rats and mice under control:

  • Keep the area around the stack or bunker tidy and free of long grass and weeds.
  • Place rat bait in bait stations on the ground around stored silage.