Bunker silos offer advantages

By Gary Sliworsky, Ag rep, Emo

This is the first of a two-part article on using bunker silos.
Bunker silos offer many advantages over tower silos for the storage of haylage and corn silage, but require careful management to minimize fermentation and spoilage losses.
Along with proper harvest moisture and length of cut, additional attention must be applied to proper site selection, sizing, filling, packing, covering, rodent control, and feed-out of bunker silos.
The invisible dry matter and quality losses as a result of poor packing and covering often are much larger than the ones you can see.
Filling silos as rapidly as possible reduces silage exposure to air and rainfall.
Bunker silos should be filled from back to front so that a “progressive wedge shape” (1:4 slope) is created, rather than filling from bottom to top.
Packing typically is the weakest link in bunker silo management. When you see a bunker silo “settle,” that actually is fermentation dry matter losses due in part to poor packing.
Dense packing reduces dry matter losses, heating problems, and storage costs. The goal is at least 17 pounds dry matter per cubic foot for corn silage, and at least 15 pounds for haylage.
Pack in thin layers of no more than 15 cm (six inches) in order to get good air exclusion and high silage density. Just be sure to take precautions to prevent tractor roll-overs.
Often there is more spoilage and poorer quality silage at the top of the pile along the bunker wall. This is because the silage is less densely packed (difficult to get in there with tractor), more exposed to oxygen (closer to the surface), and sometimes too dry (harvested last).
Sufficient tractor weight and packing time is critical. Many custom operators are capable of extremely high delivery rates to the silo, which often far exceeds the capacity of the farmer to pack adequately.
As a general rule of thumb, the number of minutes of packing required per ton of wet silage is equal to 18 divided by the tractor weight (tons). For example, a five-ton tractor requires 3.6 minutes per ton haylage or a 10-ton tractor would require 1.8 minutes.
A high delivery rate to the silo is desired, but this may mean using bigger packing tractors, adding more tractor weight, or more packing tractors in order to increase packing time per ton.
Next week’s article will deal with covering and feeding out from bunker silos.
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A risk management program information session is scheduled for Rainy River District on Tuesday, Sept. 27, 2011. Call 1-877-424-1300 to register.
If there are insufficient numbers registered, the session will be cancelled.

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