Estimating a Value for Corn Stover
Corn stover is an abundant source of winter feed for beef cows in Iowa. When supplemented with protein, vitamins, and minerals, stover can supply the nutritional needs of cows that are in moderately good body condition during fall and early winter. Corn stover is also in demand for livestock bedding and is a potential feedstock for the production of ethanol.
The obvious advantage of utilizing corn stover is its wide availability and low cost. This has created a small but important market for stover, both as a harvested product and as a standing crop in the field. As with any market, though, a price must be determined. Three general approaches can be used:
- What is the value to the purchaser, based on feedstuffs replaced by corn stover?
- What is the cost to the seller of harvesting the stover and replacing lost crop nutrients?
- What is stover selling for on the market?
Price for Harvested Corn Stover Based on Feed Value
Corn stover is often sold after it has been harvested, usually as large round bales, large square bales or small square bales. The following procedure estimates the value of baled stover to the buyer based on the cost of the feedstuffs it replaces for wintering beef cows.
Price per ton
Corn stover can substitute for medium quality mixed hay in a ration for wintering beef cows, if a protein supplement such as dried distillers grains (DDGS) is added. Table 1 shows two recommended rations, with and without corn stover, for 1,200-pound and 1,400-pound beef cows.
Price per Bale
It is not always convenient to weigh large round bales, so corn stover is often priced by the bale instead of the ton. If a typical large round bale of corn stover weighs 1,200 pounds (0.6 tons), then the value per ton can be multiplied by 0.6 to arrive at a price per bale.
This value would have to be discounted by the cost to the cattle producer of transporting the bales to the site of the cattle.
The weight of a bale will vary considerably depending on the type of baler used and the dryness of the stover. Corn stover bales typically contain only about 8 to 9 pounds of dry matter per cubic foot. Using this factor, the weight in (wet) pounds of a large round bale of 20-percent moisture stalks can be estimated as follows:
Weight (pounds) = diameter (inches) x
diameter (inches) x width (inches) x .005
Large square bales have been estimated to contain 14 pounds of stover per cubic foot. The wet weight of a square bale can be estimated as follows:
Weight (pounds) = width (inches) x
height (inches) x length (inches) x .01
The cost of chopping, raking and baling corn stover can be estimated from typical farm custom rates, such as are reported in publication FM-1698 or Ag Decision Maker file A3-10, Iowa Farm Custom Rate Survey. Rates used in Example 5 are taken from the 2011 survey. If bales must be transported, the cost of doing so should be included, as well. Wrapping the bales with plastic netting instead of twine adds about $1 per bale to the total cost. Chopping and raking may not be necessary if the combine leaves residue in a row or collects it.In addition, extra nutrients removed by harvesting must be replaced for future crops. Removal rates have been estimated at 20 pounds of nitrogen, 5.9 pounds of phosphate and 25.0 pounds of potash per ton of dry matter stover harvested (ISU Extension publication PM 1688). If stover contains 80 percent dry matter, the removal rates are 16 pounds of nitrogen, 4.7 pounds of phosphate and 20 pounds of potash per ton of wet stover harvested. These rates can vary widely depending on the hybrid planted, yields obtained, and how the stover is harvested. A forage laboratory test can be performed to find the specific analysis.
The value of the nutrients being removed can be based on the cost of commercial fertilizer, as shown in Example 6. Replacement costs of $.67 per pound for N, $.65 per pound for P, and $.61 per pound for K are assumed.
The total cost per bale represents the minimum amount the crop producer would be willing to accept, and the feed value represents the maximum the livestock producer would be willing to pay. The actual price paid may be negotiated somewhere within this range. In the examples above, the range would be from $37.05 to $40.56 per 1,200 pound bale.
Although market prices for harvested corn stover are not reported on a regular basis, bales are sometimes sold at hay auctions. Some auctions report prices on their websites, which can be located by searching on “hay auction.” Recent auction prices in Iowa for large round bales of corn stover have ranged from $30 to $40 per bale, with some sales as high as $45 per bale.
Price for Standing Cornstalks
Some corn producers have stover to sell but do not have a baler. They may prefer to sell the stover as a standing crop and let the buyer do the harvesting. In that case, the cost to the seller is only the value of nutrients removed, as shown in Example 6. The value to the buyer can be estimated as the feed value minus the cost of harvesting and transporting the bales.
The cost to the corn producer would simply be the value of the nutrients removed. In Example 6 that was estimated at $15.58 per bale, so the range of values would be $15.58 to $19.09 per bale harvested. Establishing a price based on the number of bales harvested is probably more accurate than establishing a price by the acre, because it reflects the value of the material actually removed.
Price for Grazing Corn Stover
Sometimes it is easier to bring the cows to the stover than it is to take the stover to the cows. If fences and water are adequate, stalk fields can simply be rented for grazing. Although rates vary widely, beef cows typically need about 2 acres per cow per month.
Two acres of corn stover can replace about 25 pounds of hay equivalent per day for a medium sized cow with no calf nursing, or .375 tons per month. If hay is priced at $100 per ton, the cost is $37.50 per cow per month, so each acre of stover grazed replaces $18.75 worth of hay (Example 8). However, the person renting the stover may incur some costs for providing water or fencing, and for moving the cows to the field, which reduces the affordable rent.
Some phosphorus and potassium are removed when stalks are grazed, but part of it is returned in the form of animal waste. Cattle will generally remove less stover than is removed by baling, so the cost of nutrient removal is minimal. If one cow consumes 25 pounds of stover per day, that is equivalent to .625 bales over a 30-day grazing period. Based on the nutrient removal value in Example 6 of $15.58 per bale, the cost would be $9.74 per cow. If 2 acres were grazed per cow, the cost per acre would be only $4.87 per acre. However, many of these nutrients are returned to the land in the manure. Manure may need to be broken up and spread out using an implement such as a harrow after the grazing season is over.
Cash rental rates for grazing corn stover are reported in publication FM-1851 or AgDM Information File C2-10, Cash Rental Rates for Iowa. Typical rental rates are $10 to $12 per acre per year, or for as long as grazing is practical.
AgDM Decision Tool A1-70, Corn Stover Pricer is available to estimate a price for corn stover standing in the field or harvested and stored.
Unless the lease states otherwise, stover is considered to be part of the corn crop and the tenant is free to harvest it or use it for grazing. If stover is grazed, the tenant should take responsibility for maintaining the fences and water supply. However, the owner should receive a share of any proceeds from selling stover when a crop share lease is in effect.
Soil erosion control should be taken into account when selecting fields from which to harvest stover. Avoid removing stover from fields with steep slopes, or remove only a small portion of the stover. Check the conservation plan for the farm to see if stover removal is allowed.
If half of the available stover is harvested from a field, a yield of one 1,200 pound bale can be expected for roughly every 40 bushels of corn produced. If only one-third of the stover is harvested, one bale for about every 60 bushels of corn produced could be expected. For example, if corn yielded 160 bushels per acre and half of the stover was harvested, about four bales per acre would be expected. The value of the nutrients removed, based on the estimate of $15.58 per bale from Example 6, would be about $62 per acre. For removing one-third of the stover, about 2.7 bales would be harvested per acre and the nutrient removal value would be about $42 per acre. These values can used to adjust how fertilizer costs are shared under a crop share lease. Under a cash lease, the tenant would generally make up the cost of nutrients removed by applying a higher rate of fertilizer the following year, or from applications of livestock manure.
Feedstock for Ethanol Production
Corn stover has potential as a feedstock for the production of ethanol. However, special care must be taken to avoid incorporating dirt, rocks, and other foreign material into the bales. For stover to be suitable for conversion to biofuel it must also be kept dry. This means that special harvesting and handling methods must be used when stover is to be used for ethanol, compared to using it for livestock feed or bedding. Extra costs will be incurred, which must be factored into the market price. On the other hand, the value of corn stover to the processor will depend on the costs of operating the ethanol plant, and the price of substitute products such as petroleum.
, extension economist, 515-294-6161,