Silage Insights - Bale Silage Production
Choosing and Correctly Using Stretch Film for Bale Silage

The goal of bale silage preparation is a high silage quality that does not exhibit any undesired processes of heating and mould growth. In order to reliably achieve this goal, air-tight sealing immediately after pressing of the bales and maintaining of a high quality air seal during storage are necessary. This requires a high-quality stretch film that is used properly. Important factors to be observed in practice are described below.

Film Selection
An optimal stretch film for bale silage is characterised by the following properties:

• Minimal gas permeability
• High stretching capacity
• High adhesiveness
• No irregularities, grains or reclaimed components
• Even colouring
• The layers in co-extruded films may not be separable
• High UV stability
  

These requirements are fulfilled by film types with DOWLEXTM PE resins, for example. It is important that the products are DLG-inspected (Deutsche Landwirtschafts-Gesellschaft -. German Agricultural Society) or have alternative quality certification. Such quality-certified products are somewhat more expensive, but they also offer corresponding reliability.

Film Use
Every film roll delivery should be tested before use by test wrapping of bales and inspection of its properties (see above). It has been observed in practice that time-consuming rewinding can be required in the event of faulty deliveries.

The pre-stretching of the stretch film may not be too little or too great. A range between 50 and 75% has proven optimal for allowing the film to rest closely against the bales. If the pre-stretching is too great, the stretching effect can be lost, and the film will sit loosely around the bale. In order to remain within the pre-stretching range, it is also necessary to observe the wrapper-specific rotation speed of the wrapping.

The rotations per bale and therefore the desired number of layers must also be based on the conditions of the material to be ensiled and the storage condition requirements. The older (richer in raw fibres) and drier the starting material, the more layers are required. Wrapping with 4 to 6 layers has therefore proven itself in grass silage in cattle farming using relatively fresh and rather moist material, while in horse and extensive cattle farming, 6 to 8 layers are recommended for older material that is richer in raw fibres.
Bubble-free, even stretching must be constantly maintained during wrapping. Wrapping at very high ambient temperatures (over 25° Celsius) should be avoided because the film properties could change.

The quality of the wrapping process as well as the film used (see above) result in a lightly stressed bulging of the film strips (fermentation gas build-up). This bulging is a positive sign because the fermentation gas build-up prevents possible mould growth. For this reason, bulging films must never be punctured. Generally, the fermentation gas build-up disappears on its own within 1 to 3 days.

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