Silage Bag Capacity

Silage Bag Capacity

Prepared by Brian J. Holmes
Biological Systems Engineering Department
College of Agricultural and Life Sciences
University of Wisconsin-Madison
March 26, 1999

We frequently get questions about the amount of silage in a silo bag. One way to estimate this value is to calculate the volume in the bag and multiply by its density. The volume of a round bag is calculated as:

When full length bags are used, the length of silage is the bag length minus the unused portion needed to seal each end of the bag.

The quantity of dry matter in the bag is the volume multiplied times the dry matter density. The dry matter density can vary from bag to bag and is based on machine type and adjustment as well as forage type. Typical densities range between 11-15 lbs DM/ft³. Table 1 has been developed to show silo bag capacity based on the following assumptions.

Bag Diameter	8 ft	8 ft	9 ft	9 ft
Bag Length (ft)	Silage Length (ft)	Capacity (lbs DM)	Silage Length (ft)	Capacity (lbs DM)
100	84	54,900	82	67,800
150	134	88,600	132	109,200
200	184	120,200	182	150,500
250	234	152,900	232	191,900
300	284	185,600	282	233,200

Bag Diameter	10 ft	10 ft	12 ft	12 ft
100	80	81,700	76	111,700
150	130	132,700	126	185,300
200	180	183,800	176	258,800
250	230	234,800	226	332,300
300	280	285,900	276	405,800

Use the multiplier in Table 2 to adjust the values in Table 1 for a different density. For example, the quantity of silage in a 200' ´ 9' bag packed to 15 lbs DM/ft³ is: 150,500 lbs DM ´ 1.15 = 173,100 lbs DM

TABLE 2. Multiplier to Adjust Table 1 Capacities to a Different Density.

Table 1 lists dry matter in one bag. If you need to know the capacity in lbs. of silage as fed, divide the table value by the dry matter content. For example, 65% moisture silage in a 200-foot long bag of 9 ft diameter weighs:

when packed at 13 lbs DM/ft³ density. Divide this value by 2000 lbs/T to obtain 215 TAF.

Density (lbs DM/ft³)	Multiplier
11	0.85
12	0.92
13	1.00
14	1.08
15	1.15