Corn stover consists of theleaves,stalks, andcobs ofcorn (maize) (Zea mays ssp.maysL.) plants left in afield afterharvest. Suchstover makes up about half of theyield of a corn crop[1] and is similar tostraw from othercereal grasses; in Britain it is sometimes calledcorn straw. Corn stover is a very common agricultural product in areas of large amounts of corn production. As well as the non-grain part of harvested corn, the stover can also contain other weeds and grasses.[2]Field corn andsweet corn, two different types of maize, have relatively similar corn stover.
Corn stover (like various other kinds of stover) can be used asfeed, whethergrazed asforage,chopped assilage to be used later forfodder, or collected for direct (nonensilaged) fodder use.Maize forage is usually ensiled in cooler regions, but it can be harvested year-round in the tropics and fed as green forage to the animals.[3] In the silage use case, it is usual for the entire plant (grain and stover together) to be chopped into pieces which are then crushed between rollers while harvesting. Maize silage is one of the most valuable forages for ruminants.[4] Indairy farming, corn silage is primarily used as fodder fordairy cows during the winter season. Corn stover can be beneficial tobeef cattle producers because the "corn stover can provide a low cost feed source for mid-gestation beef cows".[5] In addition to the stalks, leaves, husks, andcobs remaining in the field, kernels of grain may also be left over from harvest. These left over kernels, along with the corn stover, serve as an additional feed source for grazing cattle. Over time, the stalks will decrease in value as feed, so farmers aim to graze the corn stover as soon as possible after harvest. The amount of grazing possible on a field of corn stover is "between one and two months of grazing per cow per acre (50 cows on 50 acres (200,000 m2) for one to two months)."[5]
When corn stover is harvested intact (as opposed to the whole plant being chopped for silage, or the stover being left in the field by a combine), it can be cut and gathered by corn binders, which arereaper-binders designed specifically for maize.[6] It can also bebaled into large round bales.
Instead of feed uses, corn stover can also be collected for use asbedding or litter for the livestock (that is, cellulosic bulk to catch and contain the animalmanure), or it can be a vegetable manure that stays in the field asplant litter (serving asgreen manure, although lessgreen than some others, with a higherC/N ratio). When used as bedding (barn litter), it is then removed and directlyspread on the fields orcomposted (in long piles handled byloaders) for later field spreading. In either of the latter two use cases, it ends up asorganic matter forsoil amendment.
The feed and bedding uses of corn stover are common, but the plant litter/vegetable manure use is also common. The latter is true for any combination of two reasons: (1) it helps to maintainsoil health, and (2) when the corn crop is used as a grain crop (as opposed to a silage crop), harvesting the (grainless) stover simply does not pay; there is often no market demand for it that outweighs its value on the farm as soil maintenance, which represents an economic factor of its own. Regular annual harvesting of the whole corn plant (chopping for silage) is more challenging tosoil management than is using the corn as a grain crop and mulching the field with the stover.[7] Reincorporating the organic matter is good for the soil, although it must be managed properly to preventnitrogen robbery of the next crop, as the high C/N ratio causesavailable nitrogen (fixed nitrogen) to be hoarded by the soil microbes diligently digesting the cellulose and lignin. They can outcompete the plants for the nitrogen. There are bothorganic and nonorganic ways to augment the nitrogen supply. Animalurine andmanure is the main organic way, whereas commercialfertilizer is the main nonorganic way; both ways provideurea, which the microbes digest with theirurease.
Another use for corn stover is as fuel forbioenergy or asfeedstock forbioproducts. It can be burned in furnaces to yield energy thatsteam turbines convert toelectricity. It also has potential forcellulosic ethanol (biomass ethanol), which is "ethanol made from non-grain plant materials known asbiomass."[8] However, with current technology, a large part of thebiofuel potential ofcellulose is wasted due to the strength of theglycosidic bonds that pair chains ofD-glucose units. But if thecommercialization of cellulosic ethanol advances enough technologically, biomass ethanol production would use the corn stover from the corn crop produced in areas around ethanol plants. Corn stover, due to the relative close proximity of the corn grain produced for ethanol production, "is by far the most abundant crop residue readily available today."[8] The free accessibility to corn stover makes it a prime candidate for biomass ethanol production.DuPont opened a facility inNevada, Iowa, that was expected to generate 30 million gallons annually of cellulosic biofuel produced from corn stover residues.[9][10][11] The plant provisionally opened in 2015, but shut down in 2017 after a previous temporary shutdown in 2016. DuPont repaid $10.5 million of the $17.5 million in incentives received from the state of Iowa. DuPont sold the plant to a German company,Verbio, who converted the plant from ethanol production to renewable natural gas production for eventual use as compressed natural gas (CNG) or liquified natural gas (LNG) vehicle fuel. Humus is also produced as a byproduct of natural gas production. Humus, alternatively known as digestate, is a value-added lignin- and nutrient-rich soil amendment similar to peat moss or compost which may be returned to feedstock suppliers or further processed into marketable products. As of 2021, Verbio is considering adding back ethanol production capabilities to the plant.[12]
| Component | WT% dry[13] |
|---|---|
| Cellulose/glucan | 37.4 |
| Xylan | 21.1 |
| Lignin | 18.0 |
| Ash | 5.2 |
| GCV | 18.6 MJ/kg |
| Protein | 3.1 |
| Acetate | 2.9 |
| Arabinan | 2.9 |
| Galactan | 2.0 |
| Mannan | 1.6 |
{{cite web}}: CS1 maint: archived copy as title (link)for eventual use as compressed natural gas (CNG) or liquified natural gas (LNG) vehicle fuel. Humus, alternatively known as digestate, is a value-added lignin- and nutrient-rich soil amendment similar to peat moss or compost which may be returned to feedstock suppliers or further processed into marketable products.
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