Bunker Silo/Pile Density Study – Findings & Industry Applications

Bunker Silo/Pile Density Study –
Findings & Industry Applications
2008 Feed Dealers Meetings
Prepared by:
John Conway

Will we have adequate packing?
Major influencers of silage density --
•Tractor weight
•Packing time per ton
•Layer thickness
•Crop DM
---------------------------
(lesser extent)
•Particle length
•Height of silo

Where it all started… still basis for WI spreadsheets
Packing Density & DM Loss - Ruppel, 1992
DM loss,%
21
19
17
15
13
11
9
7
5
10 14 16 18 22
Density (lbs DM/ft3)

Bunker Silo Densities - Holmes, 1999
• Hay crop silage (87 silos)
• Average = 14.8 lbs/cu ft (6.6 - 27.1)
• Corn silage (81 silos)
• Average = 14.5 lbs/cu ft (7.8 - 23.6)
(note that these were single samples, “chest high”)

Bunker Silo/Pile Density Study – Describe Silo Filling Dynamic Relative
to DM Densities:
124 Samples from 68 Silo Faces
Legume, Grass, Mixed, Corn Silage & BMR CS
2004 2008, Most in 2006 & 2007 Crop Seasons
Led us to these conclusions…

What We’ve Found:
University of Wisconsin spreadsheets for predicting density of
bunkers and piles remain the most reliable tool out there. But…
- Legumes, particularly when drier, tend to run slightly higher
than predictions. The “glueyness” factor.
- Corn silage trends slightly lower than predictions – sometimes
due to loads being dumped faster than you think they are.
- Grass really resists compression. It is also tough to blade as it
wants to roll. We need more data. Same equipment and delivery
rates and it’s up to 5 lbs./ft. 3 lower. More storage needed!
You can use your own “tested” density predictions to arrive at a
“smaller silo space required” compared with average densities. This
allows bunkers or piles to be compared fairly with other storage
systems or with each other. (See “Cost of Forage Storage” spreadsheet)

What We’ve Found… continued:
Water trapped in plant material occupies space. Wetter materials
do not achieve the dry matter densities of similarly packed drier
materials.
-Top notch packing does not help with consequential
fermentation problems (i.e. butyrate) when silage is put up
too wet (

What We’ve Found… continued:
While dry matter losses translate easily into dollars, it is the cost
of additional storage needed with sub-optimal densities that really
drives up storage costs.
A haylage silo filling strategy that seems to work well… use a long
ramp to keep blade layer minimized. When stretching out the life of
silo; layering a subsequent cutting on top and in front of initial
cutting will compress the lower material even more. Useful when you
need to stretch the utilization of a silo while minimizing losses.
When corn silage (or haylage) is so far over the sidewalls that it looks
like a bread loaf, it’s time to consider more packing weight or even
better, a new silo! A lot of diesel and labor is spent on not a lot of
dry matter!

Closer L k – Straight Grass
Grass “Rolling”
, “Ridging”
& “Springing Back”
Mvi_0240.avi

Closer L k – Storage Costs
Horizontal Silo
What’s Happening in that Cubic Foot
of Bunker Silo Storage “Space”?
32’W x 106’L x 10’H = 33,900 ft. 3
Capital Cost structure plus share of tractors = ~$61,000.
Capital Cost per ft. 3 = $1.80
Annualized Capital Cost per ft. 3 (10 yr. depreciable life) = $0.18
13 lbs. forage DM/ ft. 3 density @ 17.5% storage loss = 10.7 lbs./ft. 3 retained
18 lbs. forage DM/ ft. 3 density @ 13.4% storage loss = 15.6 lbs./ft. 3 retained
Value of 10.7 lbs./ft. 3 @ $0.05/lb.* over 33,900 ft. 3 = $18,136.00
Value of 15.6 lbs./ft. 3 @ $0.05/lb.* over 33,900 ft. 3 = $26,442.00
A 38% difference in packing density amplifies to a 45.8% difference in forage $
value retained and fit into “space”. A $8,306.00 difference in retained forage value.
Net value of forage losses due to lower density = $1271.00
…but you may still need to find a home for 4.9 lbs. DM/ ft. 3 you need as feed that
did not fit into the “space”. At $0.18 annualized capital cost per ft. 3 = $2300.00
Wasted silo “space” costs are additive to DM losses – twice the $ value!!
*Value of $35.00/ton haylage at 35% Dry Matter (DM), converted to 100% DM and expressed in pounds

Closer L k – Storage Costs
The “Beast”
(dozer that is)
110,000 lbs. of
packing force

Closer L k – “Re-Packing”
4 th/ 5 th Crop
18.4 lbs./ft. 3
over 3rd
17.6 lbs./ft. 3
over 3rd & 1st
3 rd Crop
17.0 lbs./ft. 3
sole face
19.0 lbs./ft. 3
over 1st & under 4 th /5 th
1 st Crop
17.6 lbs./ft. 3
sole face
23.8 lbs./ft. 3
under 3 rd & 4 th /5 th
Each new crop came over the top of what was
below and had a full face of its own on the front side. Peak
height is 6’ over side walls. Little or no waste. Trucks dump
fresh forage onto a concrete backwall/landing area that is just
below the top of the sidewalls.

Closer L k – Overtopping
The “breadloaf” top – 10’+ above sidewalls. Dry matter density of only
12.8 lbs./ft. 3 at 6’ from top, means a lot of diesel and tractor labor are
burnt for not a whole heck of a lot of feed-able corn silage. Pad work is
done for new silo with shared sidewall (into use Fall, 2008).
2007

Useful Tools to Integrate Forage Production
with Feeding System at the Silo
(CD of Related Wisconsin Spreadsheets)

Useful Tools to Integrate Forage Production
with Feeding System at the Silo (continued)
(CD of Related Wisconsin Spreadsheets)
*Bunker Silo Density Calculator (English & Spanish)
BunkDensCalc8-24-07wPOROSITY.xls (spreadsheet)
Documentation: BunkDensityCalcDoc2-28-06.doc
Dr. Brian Holmes &
Dr. Richard Muck
Univ. of Wisconsin
Inputs:
Silo wall height
Maximum height
Silage delivery rate
Silage DM content
Silage packing layer thickness
Packing tractor(s) weight(s)
Outputs:
Wet density
Porosity
DM density

Useful Tools to Integrate Forage Production
with Feeding System at the Silo (continued)
(CD of Related Wisconsin Spreadsheets)
*Silage Pile Density Calculator (English & Spanish)
PileDensCalcwPOROSITY8-24-07.xls (spreadsheet)
Documentation: PileDensityCalculatorDoc2-28-06.doc
Dr. Brian Holmes &
Dr. Richard Muck
Univ. of Wisconsin
Inputs:
Bottom width
Height
Top width
Side slope (if known)
Silage delivery rate
Silage DM content
Silage packing layer thickness
Packing tractor(s) weight(s)
Outputs:
Wet density
Porosity
DM density

Packed pile with same tonnage stored as last bunker silo –
best density achievable is 9% lower (16.6 vs. 18.1 lbs./ft. 3)

Useful Tools to Integrate Forage Production
with Feeding System at the Silo (continued)
(CD of Related Wisconsin Spreadsheets)
*Determining Value of Improved Silage Management
FeedLo$$5-6-08.xls (spreadsheet)
Documentation is a sheet (tab) within spreadsheet
Dr. Brian Holmes,
Univ. of Wisconsin
Inputs:
Animal numbers
DM consumption
Ration ratio of haylage:corn silage
Haylage $ value
Corn silage $ value
Loss values – before
Loss values – after
Output:
Bottom line – Total improvement in value lost, $/year

Useful Tools to Integrate Forage Production
with Feeding System at the Silo (continued)
(CD of Related Wisconsin Spreadsheets)
*Cost of Forage Storage Spreadsheet
(Capital investment & annual costs of forage storage)
(Ideal for comparing costs of bunkers vs. piles)
(Has bunker silo sizing spreadsheet (above) embedded as tab)
CSTFORST5-1-03.xls (spreadsheet)
Documentation: for-stor.pdf
Dr. Brian Holmes &
Dr. Gary Frank
Univ. of Wisconsin
Inputs:
Very detailed, all possible costs
Helpful calculators for different cost cells
Can ignore other types of storage not wanted in comparison
Relative cost of concrete vs. macadam may swing results over time
Choosing bunker vs. pile generally has other factors to consider beyond cost alone
Outputs:
Total annual storage cost ($/year)
Annual storage cost per ton of DM ($/ton)
Annual storage cost per ton of DM fed ($/ton)

Project’s contribution to
farm’s Forage Feed Flow
operations management:
Real time, web-based,
silo inventory management
software.
http://www.agmodels.com/clients/silostor/
Why web-based?
Speed & capacity of server
Greater programming flexibility & efficiency
Continuous enhancements/upgrading without user disruptions

You will receive an e-mail – click
through and you’re in!

Why use tools?
Help in Complicated
Decision Making
Dynamic
Have Competing Related
Investment Needs and Wants?
*Current Operational Bottleneck(s)
-Mowing capacity
-Merging capacity
-Chopping capacity
-Hauling capacity
-”Blading” capacity
-Packing capacity
-Available quality labor
for all above
-Functional silo capacity
What are Short/Long
Term Goals?
*Need to get more storage
out of existing space.
(Pack it in tighter)
*Want to limit DM losses
*Both of the above
Spend Labor
and/or Machinery
Dollars on More
Intensive Packing?
What’s Driving Demand to
Conserve the Most Possible?
*Acres available
*Yield per acre
*Total Herd Forage DM Needs
-Current “steady state”
+ with optimum quality
+ at maximum inclusion rate
+ want/need future expansion
Want to Mitigate Risks
Associated with Mother Nature?
*Are you willing to gamble
on 1 st crop weather window
“length” in days? 2006 was
really only 4 – 5!
*Soil related constraints
under saturated conditions

Benefits Experienced by Project Farms
“Guy with clipboard” effect; big response in added tractor
weight and packing intensity.
Gains in inventory carried over – even in modest yield years
like 2006 & 2007 crop seasons.
Inventory gains are very real. Opens door to some
interesting options:
- Grow herd if in position to do so
-Shift rotations to mix of hay and corn that best suits
land resource
-Divert some acreage to energy and/or protein grain
production
-Some profit generating combination of the above

Let’s end with the start of a well-packed pile…