Silage density and packing explained
Why packed density drives silage tonnage, what moves the 40 to 50 lb per cubic foot range, and how to pick a number.
Why density matters more than size
The dimensions of a bunker set an upper bound on volume, but density decides how much feed that volume actually holds. Two piles of the same length, width and height can differ by a quarter or more in tonnage purely because one was packed harder than the other. That is why the calculator asks for density as a separate input rather than assuming a fixed weight per cubic foot. Getting the density right is the single biggest lever on an accurate estimate.
What moves the 40 to 50 range
As-fed corn silage commonly lands between 40 and 50 pounds per cubic foot. Chop length, moisture, and above all packing tractor weight and layer thickness push a stack toward the top of that band. Thin layers packed by a heavy tractor exclude air and reach the higher densities, while thick, fast-dumped layers trap air and settle lower. Moisture also counts, since wetter forage weighs more per cubic foot but stores less dry feed. The default of 44 is a reasonable midpoint when you have not measured your own.
Measuring your own density
You do not have to guess. Track the tons of forage delivered to the bunker across a scale, then measure the packed volume once filling is done. Dividing total pounds by cubic feet gives a real density you can plug straight into this tool for future estimates on the same structure. Coring the face with a probe and weighing a known volume is another way to check, and it captures how the pile settles over weeks of storage. A measured number beats a table value every time.
From tonnage to days of feed
Once you trust the tonnage, turn it into feeding days. Divide the as-fed tons by the herd's daily as-fed silage intake to see how long the stack lasts, remembering to allow for shrink and spoilage at the face. If you feed on a dry matter basis, convert the tons using your forage test first, then divide by dry matter intake. Planning this way tells you whether a bunker carries the herd to the next harvest or whether you need to stretch it with other feeds.