Harvesting Both Corn Grain and Stover in Adverse Weather

NDSU quantifies the cost and time involved in corn stover collection
By Cole Gustafson, Thein Maung and David Ripplinger | August 15, 2011

If cellulosic biofuel development remains on track, several commercial firms will be contracting for corn stover in 2012.  How will farmers balance the field workload of harvesting both feed grains and corn stover in a year like this one when the crop is late and field days before winter are limited? How much incentive will cellulosic firms have to offer producers to ensure feedstock collection is a priority?

The research team at  North Dakota State University in Fargo recently completed a Sun Grant study, sponsored jointly by the USDA and the U.S. DOE, that addresses the impact of limited fall harvest field time, the availability of new corn cob and stover harvesting machines, increased farm sizes, and alternative tillage practices. A large, mathematical program model of a North Dakota farm with 2,000 acres of 144-bushel-per-acre corn to harvest considers 1) corn grain harvest only, 2) simultaneous corn grain and stover,  one-pass harvest, and 3) separate corn grain and stover, two-pass harvest options.  

Corn grain was harvested with a 275 horsepower (hp), $335,000 combine operating at 4 miles per hour (mph).  When stover was collected with a $120,000 machine attached directly behind the combine, its speed was assumed to drop by half to 2 mph based on prior trials at Chippewa Valley Ethanol Cooperative (CVEC) and a GIS study of combine/harvester performance at Iowa State University. Slowing harvest rates has a dramatic impact on machine operating costs, as shown in Table 1.
In the two-pass system, where grain is combined first and stover is collected later with a 130 hp, $120,000 tractor and $100,000 large, square baler, harvest pace is not reduced as the combine operates at full speed of 4 mph while the tractor/baler operates at 5 mph. Total cost per acre is $28.71 for combining, as before, plus $10.76 for the baling operation.

Climatic conditions, and thus corn yields, vary substantially across North Dakota. The study utilizes a corn growth model to estimate the total amount of corn stover available by region based on historical grain yield. It further assumes that only 35 percent of available stover or cobs are collected due to wind, water and soil erosion, carbon maintenance, and other environmental considerations. The state map shows the tons of stover and cobs available for use as cellulosic feedstock in each region.
The number of days that are available each fall for farmers to harvest grain are recorded by USDA’s National Agricultural Statistics Service, and shown in Table 2. Surprisingly, the most difficult harvest time is early to mid-October. Farmers typically harvest soybeans during this time, so any weather delays impact corn harvest, which immediately follows. Few harvest days exist after November due to the threat of snow.

The base analysis that estimates the profitability and timeliness of harvesting corn grain only is summarized in Table 3. The main decisions the farmer must make are the number of corn acres to plant and the size of combine to assure that most of the crop is harvested in a timely manner, given limited fall harvest days. By planting 2,000 acres of corn and investing in a 275 hp combine, the farmer nearly completes harvest, given average weather risks. With corn priced at $4 per bushel, he earns $382,338 net profit after all crop production expenses are deducted.

One-Pass Harvesting

Collecting corn cobs with an additional machine attached to the combine presents the farmer with an additional decision. Collecting and selling cobs provides farmers with additional revenue. We assume they receive $55 per ton based on rates paid to producers who participated in corn cob collection projects in the Midwest. The downside of collecting cobs in a one-pass system is the risk of not harvesting all of the corn acres due to combining at reduced speed with limited fall harvest days. Table 4 shows the results of the one-pass system analysis.

With additional corn cob revenue of $55 per ton, net profit increases from $382,338 to $401,443 on average, providing that the addition of the cob collection machine does not slow combine operating speed. If the combine operating speed is reduced by 50 percent, net profits decline substantially to $244,208 and nearly 500 acres of corn remain unharvested.

Thus, the key to farmers collecting corn cobs in the future is the technology of new equipment and the degree to which the machine impacts combine efficiency. Farmers may be willing to tolerate minor reductions in combine efficiency if cellulosic buyers increase payments to defray producers profit shortfalls. 

Two-Pass Harvesting

The final stover collection system evaluated is the two-pass system where corn grain is combined first at full efficiency and stover is baled later as a separate operation. Here, the farmer must decide if the value of stover is high enough to warrant investment in a baler, additional tractor operating costs, and corn grain sale losses from having to park the combine to enable stover baling before winter. Results of this method are shown in Table 5.

In this system, with additional corn stover revenue of $45 per ton, net profit is about $345,285, and 234 acres of corn grain are not harvested. Because the farmer has to operate the tractor/baler in addition to the combine, he simply doesn’t have enough time to get everything done. Even doubling the price paid for stover from $45 to $90 per ton only provides additional profit of $27,929 on the 2,000 acres of corn, which only partially offsets the income loss of $135,248 from unharvested acres.
In other analyses, we consider larger and smaller farm sizes and reduced or minimum tillage as a means of defraying the profit losses associated with the additional time required to collect stover. None of the systems considered match the profitability of traditional corn grain combining unless the stover collection machine has zero impact on combining efficiency.

A frequent suggestion is for farmers to hire additional labor to drive the tractor/baler. Additional farm labor, however, is difficult to find in rural areas, especially in North Dakota. At present, the state has the lowest unemployment rate in the nation. Moreover, large tractors and new stover collection equipment is highly sophisticated and any new farm laborer would need extensive training and oversight, again burdening a farmer who is already busy.

Authors: Cole Gustafson,
Biofuel Economist, North Dakota State University

Thein Maung
Biofuel Researcher, NDSU
David Ripplinger
Biofuel Researcher, NDSU