Agrimetra

Silage pile calculator

A bunker 30 ft wide, 10 ft deep and 90 ft long, packed at 44 lb/ft³, holds 594 tons of silage as fed (538.9 t) in 27,000 ft³. At 32 % dry matter that is 190.1 tons of feed — 144 days for 120 cows eating 22 lb of silage dry matter a head a day.

The answer updates as you type — there is no button to press.

e.g. 40 ft.

e.g. 12 ft.

e.g. 120 ft.

e.g. 44 lb/ft³ as fed.

%

Corn silage is around 35 %.

For the feed-out days line.

Only the silage part of the ration, as dry matter — e.g. 24 lb (11 kg) for a milking cow.

Your answer

Silage in the store, as fed1,267.2 ton

In tonnes
1,149.6 t
Dry matter in it
443.5 ton
Volume
57,600 ft³

Field job sheet

Add head to feed and daily intake below to see how many days this store feeds the herd.

How the answer is worked out

The tonnage of a silage store is its shape’s volume times how hard it was packed:

Then:

volume × packing density = tons as fed → × dry-matter % = tons of dry matter → ÷ (head × daily silage dry matter) = days of feed

The pile weighs more than it feeds

Two-thirds of a corn silage pile is water. That is why the page prints the dry matter next to the as-fed tonnage, and why the feed-out days are built on dry matter: a wetter crop weighs more in the pile without feeding a single extra day.

Why measured density beats a table

Packing density varies with the crop, its moisture, the tractor weight and the time spent packing each layer, and it is what turns a volume into tons. Two piles of the same size can differ by a fifth in feed. A few core samples taken at the face and weighed give a density for this pile, and every figure on the page follows it.

Using the days line

  1. Compare with the calendar. If the pile feeds 144 days and the next harvest is further away than that, the gap is visible now, not in spring.
  2. Allow for shrink. Fermentation, the face and the top layer all lose dry matter; the page counts what is in the pile, not what reaches the cow.
  3. Recalculate at the face. Measuring what is left mid-winter gives a second estimate against the first.

A worked example

Every figure below is computed by the calculator above from this case — nothing here is typed in by hand:

Store
Bunker (straight walls)
Measured in
ft
Width at the base (bag: diameter)
30
Height
10
Length
90
Packed density
44
Density unit
lb/ft³
Dry matter
32
Head to feed
120
Daily feed weighed in
lb
Silage dry matter per head per day
22

Silage in the store, as fed:594 ton

In tonnes
538.9 t
Dry matter in it
190.1 ton
Volume
27,000 ft³
Total for the whole field
144

Worked by Agrimetra with the same engine the calculator above runs.

What this means in the United States

Bunkers and piles are measured as fed and fed as dry matter, and a corn silage clamp is roughly two-thirds water, so tonnage in the pile and tonnage in the ration are different numbers. Feed-out days for the herd is the figure that decides whether the pile is big enough.

Questions growers actually ask

How do I calculate tons of silage in a pile?
Volume times packing density. A bunker is a box; a drive-over pile is a wedge, so the calculator asks for the width across the top as well as at the base; a bag is a cylinder. The volume in cubic feet times pounds per cubic foot, divided by 2,000, is tons as fed.
What packing density should I use?
Measure it if you can — core samples from the face, weighed, are the honest figure. Well-packed corn silage is often around 40 to 45 lb/ft³ as fed; a poorly packed pile is lighter and spoils faster. The density drives the tonnage directly, so a guessed figure makes a guessed answer.
Why are there two tonnages?
Corn silage is roughly two-thirds water. Tons as fed is what the pile weighs and what the wagon carries; tons of dry matter is what the cows eat and what the ration is built on. The feed-out days are calculated from dry matter so the answer does not depend on how wet the crop went in.
What daily figure do I enter for the herd?
The silage part of the ration, as dry matter per head per day — not the cow's whole intake. A milking cow eating a corn-silage-based ration may get something like 20 to 25 lb of her dry matter from silage; take the figure from your ration sheet, in pounds or kilograms.

Last updated:

Sources

Calculators that use the same field