Questions Relative to Harvesting & Storing Corn Stover
Dr. R.L. (Bob) Nielsen
West Lafayette, IN 47907-1150
Office ph. 765-494-4802
Prepared September 1995. Originally published as Agronomy Extension
publication AGRY-95-09. Contact the author for hardcopy versions of this
This document addresses some questions regarding the harvesting and storage
of corn stover for the purpose of delivery to a proposed corn-based pulp mill in
northwest Indiana. Some of the responses to these questions are based on Purdue
Extension writings from the 1970's when harvested corn stover was being
evaluated as an alternative energy source for beef cattle. Additional thoughts
on these issues are based on recent discussions between Bob Nielsen (Purdue
Agronomy Dep.), Sam Parsons (Purdue Ag. & Biological Engineering Dep.), and
Dave Petritz (Purdue CES AgNR). We don't pretend to presume to have addressed
all the considerations that apply to this venture. We have also restricted our
comments to the harvesting and storage of the stover, since we have no knowledge
of the pulp-making process itself.
What is the farmer obligated for?
- A farmer must purchase a minimum of four units of equity interest ($10,000)
in a paper-pulp mill to be constructed by Heartland Fibers Inc., plus a $250
- Purchase of equity interest in the paper-pulp mill obligates the farmer to
produce a minimum of 252 tons of corn stover at a yet-to-be-determined stover
- The farmer agrees to allow access to the enrolled acres after grain harvest
for the purpose of stover shredding, windrowing, baling, and transport of corn
stover by custom operators under contract to Heartland Fibers, Inc.
- The farmer also agrees to store some or all of the large bales on-site
until the production plant calls for delivery.
What are the risks involved with corn stover harvest?
- We estimate that the average harvest window to shred, windrow, and bale
corn stover will be 40 days after corn grain harvest, after which weather and
soil conditions are often not conducive to field traffic and stover harvest.
- Wet weather and muddy fields during and after grain harvest would delay or
prevent stover harvest. This is especially critical given the likely dependency
on the schedules of custom operators who will be responsible for
shredding/windrowing/baling the corn stover.
- Soil compaction and ruts can easily result from extra wheel traffic on
excessively wet soils.
- Stover moisture content greater than 30 percent would likely decrease the
efficiency of the baling operation, and also decrease the storability of the
bales due to increased risk of molding and rotting.
- Corn stover material will generally cause greater wear and tear on
harvesting equipment than does alfalfa and grass hay.
- There may be opportunity costs relative to competing fall farm operations.
How much stover is produced in a typical corn field?
- Corn grain accounts for about 45% of the total dry matter yield of a corn
field. Corn stover amounts would range from 3 to 4.5 DRY tons per acre in
fields ranging from 100 to 150 bushels of grain per acre. DRY ton means exactly
that; 2000 lbs. of totally dry stover. You can convert wet weight to DRY weight
by multiplying the wet weight by the percent dry matter.
- If 60 percent of the stover would be harvested, then harvested stover
amounts would range from 1.8 to 2.7 DRY tons per acre depending on grain yield
level. At a stover moisture content of 30 percent, the range of harvested
stover would translate to 2.6 to 3.9 tons per acre.
What are the effects of stover removal on soil tilth?
- Hard to estimate, but surface organic matter levels would decrease and
equilibrate to a lower level if corn stover were harvested frequently over a
period of time. Therefore, we would recommend rotating fields to be harvested
for stover from year to year.
What are the effects of stover removal on ground cover and HEL
- Heartland Fibers Inc. estimates that 40 percent of the corn stover will be
left in the field after stover harvest.
- Less ground cover would increase the risks of soil erosion from heavy
- Removal of 60 percent of the stover material would NOT leave
sufficient ground cover to satisfy conservation compliance program regulations
the following spring, especially if much of the remaining residue was composed
of standing stalks.
What is the approximate value of stover nutrients removed from field?
- The approximate amounts of nitrogen, phosphate, and potash removed per DRY
ton of harvested corn stover are 13.6, 3.6, and 19.7 lbs. (Adapted from Voss,
R. 1993. Nutrients in corn and soybean residue. Integrated Crop
Management Newsletter, IC-466(26), Nov 1, 1993. Iowa State Univ., Ames, IA.)
- The approximate value of the nitrogen, phosphate, and potash per DRY ton of
harvested corn stover is $2.72, $0.79, and $2.36 (based on $0.20, $0.22, and
$0.12 per lb. of nitrogen, phosphate, and potash fertilizers), for total
nutrient value of $5.87 per DRY ton.
- If harvested stover amounts ranged from 1.8 to 2.7 DRY tons, then the total
value of the nutrients removed from the field would range from about $11 to
$16 per acre.
What type and size of package (bales, stacks) is desired?
- The most feasible package would likely be 1-ton bales measuring 4x4x8 ft,
produced by the Hesston Big Baler. Such bales are relatively high density,
solid, and suitable for transport on a flatbed semi-trailer.
- Other possibilities include large round balers (1/2 ton bales) or stackers
(1/2 to 1 ton stacks).
Is any pre-harvest operation, such as windrowing, necessary?
- Yes, quite likely the stover will need to be cut with a rotary hay cutter
and raked with a double rake prior to harvesting the stover. A combination
flail chopper/windrower could also be used.
- Keep in mind that the tire traffic of the grain harvest operation (combine,
grain carts, trucks, etc) will make some percentage of the stover very difficult
What type of custom harvesting and transport equipment will be required?
- A combination flail chopper/windrower to prepare the stover for baling.
- A baler to bale the windrowed stover into large bales. As a frame of
reference, the Hesston Big Baler sells for at least $50,000. Heartland Fibers
Inc. states that only wire tie bales will be acceptable.
- Flatbed trailers or semi-trailers to haul bales to plant.
What is the optimum stover moisture content for harvest?
- Stover moisture content should probably not exceed 30 percent for optimum
- As a rule of thumb, percent moisture content of stover is twice that of the
grain. For example, the moisture content of stover when you harvest grain at 20
% moisture would be about 40 % moisture.
Where and how will stover be stored?
- The farmer is responsible for storing the stover packages until the
processing plant calls for delivery.
- Heartland Fibers Inc. states that 'fiber degradation caused by excessive
moisture levels in the baled stover' will result in adjustments in their
purchase price to the farmer.
- Heartland Fibers Inc. states that storage site requirements and
approved field site locations will be defined in their criteria.
- It is our opinion that to best maintain quality of the stover packages,
they should be wrapped and stored on crushed rock or under cover. Depending on
the length of time these packages will need to be stored, stover moisture
content may need to be 20 % or less.
- Because of the uncertainty of when the plant will call for delivery, the
stover packages should be stored on sites that will not interfere with normally
scheduled fall or spring field operations.
What is the cost of harvesting and transporting corn stover packages?
- Cost per dry ton of stover to custom harvest will average $8 to $10 per
package. Cost of cutting and windrowing the stover prior to harvest will
average $4 to $6 per acre. Cost of transporting packages (several miles only)
will average $2 to $6 per package. (Source: Purdue Custom Rates, 1994)
- Apparently, the pulp-mill operation will contract directly with custom
harvesters and transporters.
The Corn Growers Guidebook , a WWW resource for
corn management systems in Indiana and the eastern CornBelt.
The Chat 'n Chew Cafe.
Purdue University Agronomy Extension WWW
Purdue Agronomy On-Line! , Purdue's Agronomy
Department WWW Home Page.
End of Document