From 2007 to 2011, an average of 108.5 million tons of whole-plant corn was harvested annually for silage in the U.S. The majority of corn silage was stored in bunker silos and drive-over piles. But filling bunkers and piles can pose serious risks to employees, especially those who operate the pack tractors, unless safety guidelines are put in place in advance.

Bolsen keith
Professor Emeritus / Kansas State University
Bolsen was a contributor to Progressive Dairy and Progressive Forage before passing away in 2020.

el_english_crossover 1. Properly equipped tractors can prevent tractor rollovers
• Make sure the tractor you operate is equipped with rollover protective structures (ROPS) and seat belts. When used with a seat belt, ROPS prevent the operator from being thrown from the protective zone and crushed by the tractor or equipment.

• Low-clearance, wide front-end tractors equipped with well-lugged tires help prevent slipping.

• If additional weight is needed to improve stability, consult with the dairy owner to add weights to the front and back of the tractors.

2. Safety guidelines for bunker silos
• Keep an eye on mounted sight rails of aboveground walls. These rails indicate the location of the wall but are not intended to hold an overturning tractor.


• If filling will occur at night, make sure any lights installed on the rails are working properly in order to avoid driving over dark areas.

• Never use large rectangular or round hay or straw bales as temporary bunker walls.

3. Proper packing technique
• Attend “silage team” meetings and discuss the packing procedure before the harvest begins. Be sure to fully understand your role during the entire packing process.


• Only mature, experienced employees should be permitted to operate pack tractors.

• When packing, form a progressive wedge of forage and maintain a minimum slope of 1-to-3. Maintain a minimum slope of 1-to-3 on the sides and ends of drive-over piles.

• Back tractors up steep slopes to prevent rollbacks.

• When using front-end loaders to move forage to the bunker or pile, do not carry the bucket any higher than necessary to help keep the center of gravity low.

0312el_bolsen_1 • If two or more pack tractors are used, establish a driving procedure with the other tractor operator(s) to prevent collisions.

• Do not fill bunker silos higher than the top of the wall.

Tractor rollover accidents account for about 50 percent of the tractor-related fatalities reported annually. Think safety first – packing accidents can be prevented if these safety guidelines are put in place. EL

Ruth E. Bolsen is the managing director of Keith Bolsen & Associates.

TOP: When two or more pack tractors are used, establish a driving procedure to prevent collisions.

MIDDLE: Never fill bunker silos higher than the top of the wall. A straight drop off of a bunker wall is a significant risk.

BOTTOM: Failure to maintain a minimum 1-to-3 slope on the sides of a pile increases the risk of a tractor rollover. Photos courtesy of Keith Bolsen.


Keith Bolsen
Professor emeritus
Kansas State University