Why is high silage density important?

Monday 6 November 2017

Silage density and loss of Dry Matter (DM) are negatively related. Higher silage densities also increase the storage capacity of existing bunker silos and can decrease the height and footprint of drive-over piles.

Silage density should be as high as possible to reduce the amount of oxygen (air) in the silage mass. To achieve this a high tractor weight is required.  But beware of overloading side walls. Check wall load capacity and pack tractor weights before filling.

 Recommended minimum silage density is 700 to 750 kg fresh weight/m3 (230 to 250 kg DM/m3).

Walls must be sufficient distance apart to allow tractors to be operated safely and efficiently. If not, then two or more bunker silos should be filled simultaneously to accommodate the tractors.

If forage DM exceeds 40%, packing tractor weight must be increased to reach target silage density. 

Key considerations to increase silage density:

1. Good communication. If forage delivery rate to the silo increases, be prepared to add an extra or heavier pack tractor.

2. Estimate likely silage delivery rate to the silo and predict silage density before harvest begins by using spreadsheet software (http://www.silo.org/bunkerdensity.xls). Be prepared to adjust harvesting, filling and packing procedures.

3. Employ well-trained and experienced people, especially those who operate the push-up/blade tractor(s). Provide training as needed.

4. Spread forage in uniform layers of 15 cm or less; and pack continuously throughout filling.

5. Form a progressive wedge of forage and maintain a slope no steeper than 1 in 3 or 18 degrees.

6. Abut the pack tractor tire with the track of the previous tractor pass.

7. Ensure at least two pack tractor passes over the surface of each layer of forage.

8. Drive-over piles should be packed from side-to-side, as the progressive wedge advances, and the sides of the pile should never exceed a slope of 1 in 3.

9. When two or more pack tractors are used, establish a safe driving procedure.

10. When possible, drive up and reverse down packing slopes.

11. Do not drive tractors in a circle and avoid making 180-degree turns on the floor of a bunker or front apron of a pile.

12. Increase pack tractor passes near the walls of bunker silos to increase the density of the forage that is within one meter of the wall;

13. Make a concave shaped top while filling and finish with a convex top to shed water to the sides.

 Tracked bulldozers and vibrating rollers can be used. Their heavy weight and vibration can achieve higher silage density. Tracked vehicles are likely to be more stable on the sloped surface of low DM forages than wheeled loaders. Towed packing devices and earth packing machines, including rail wheels have been used to increase silage density.