Corn stover consists of the leaves, stalks, and cobs of maize (corn) (Zea mays ssp. mays L.) plants left in a field after harvest. Such stover makes up about half of the yield of a corn crop and is similar to straw from other cereal grasses; in Britain it is sometimes called corn 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. Field corn and sweet corn, two different types of maize, have relatively similar corn stover.
Composition and properties
Corn is the most important agricultural grain crop and is used worldwide from tropical to temperate climates. The availability of maize straw depends on soil conditions, topography, crop rotation and environmental conditions. The amount of sustainable maize straw is limited as part of the straw must remain in the field to provide adequate protection against soil erosion by water and wind, and not to reduce the carbon and nutrient balance of the soil to overload. Estimates suggest that between 20 and 80% of maize straw can be sustainably harvested.
The two most important corn and maize straw producers are the United States of America (USA) and the People’s Republic of China. For the USA, maize straw volumes of 200 to 250 million dry tonnes are quoted. For China 200 to 220 million dry tons, of which an estimated 90% are removed from the field. For Belgium, quantities of 580 000 dry tonnes are given, of which an estimated 290 000 dry tonnes can be harvested economically. For Germany, annual quantities of 3.8 million tonnes of dry matter are given, but these have not yet been harvested.
Advent and recovery
The corn-straw ratio of grain maize is about 1: 1.3, so that with a mean grain yield of about 6.8 tonnes per ha per year theoretically 9 tonnes of crop residues in the form of maize straw remain in the field. Due to the harvesting technique, the actual amount of residues is probably much lower. As with other straw fractions, especially the straw of cereals, a large part of the accumulating amount of straw remains chopped on the field as a humus-forming substrate.
A material or energetic use of maize straw occurs rarely. This is partly due to the limited possible recovery of Maistrohaufkommen and the high water content of the harvested biomass, which would require a complex drying of the thick stems for processing. In some regions, corn after harvest is dried in bundles in the field and can then be collected and used. However, in terms of fuel properties, dry maize straw hardly deviates from cereal straw, with a calorific value of 18.9 MJ / kg and a calorific value of 17.7 MJ / kg.
Corn stover (like other types of crop residues) can be used as livestock feed, especially in forage deficit situations. They have a slightly higher nutritional value than wheat straw. They are used either in green as pasture, or after chopping as silage for later use, or harvested for direct distribution (without silage). In the case of silage, it is usually the whole plant (foliage and ears) that is chopped and then crushed between rolls during harvesting. It is necessary however that the rate of dry matteris not too high to allow good conservation. It is often between 50 and 60%.
In dairy farming, corn silage is mainly distributed to dairy cows as fodder during the winter season. Corn stover can be beneficial for beef producers because “corn stalks can provide a low-cost source of feed for mid-gestating suckler cows”.
In addition to the stems, leaves, husks and stalks left on the field, grains can also escape the harvest. These abandoned grains are, along with other crop residues, an additional source of feed for grazing livestock. The nutritional value of stems decreases over time, so farmers seek to graze corn residues as soon as possible after harvest. The amount of grazing possible on a post-harvest corn field is “between one and two months of pasture per cow per acre (50 cows on 20 hectares)”.
When corn canes are harvested intact (as opposed to chopping the entire plant for silage, or corn cane left in the field by a combine harvester), they can be cut and gathered by corn briers, which are combine harvesters designed specifically for corn. They can also be compressed and wrapped in the form of large round bales.
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 are reaper-binders designed specifically for maize. It can also be baled into large round bales.
Bedding (litter) followed by soil amendment
Instead of feed uses, corn stover can also be collected for use as bedding or litter for the livestock (that is, cellulosic bulk to catch and contain the animal manure), or it can be a vegetable manure that stays in the field as plant litter (serving as green manure, although less green than some others, with a higher C/N ratio). When used as bedding (barn litter), it is then removed and directly spread on the fields or composted (in long piles handled by loaders) for later field spreading. In either of the latter two use cases, it ends up as organic matter for soil amendment.
Instead of using them as livestock feed, corn canes can also be harvested for use as bedding for livestock or other livestock (ie, as a cellulosic mass to fix and contain excreta). animal ), or can be used as vegetable manure that remains in the field and enriches the plant litter (used as green manure ). When used as litter, they are then removed and spread directly into fields or composted (in heaps handled by mechanical loaders ) for later application in the fields. In the latter two cases, they end up asorganic matter to improve soils.
Direct soil 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 maintain soil 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 to soil management than is using the corn as a grain crop and mulching the field with the stover. Reincorporating the organic matter is good for the soil, although it must be managed properly to prevent nitrogen robbery of the next crop, as the high C/N ratio causes available 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 both organic and nonorganic ways to augment the nitrogen supply. Animal urine and manure is the main organic way, whereas commercial fertilizer is the main nonorganic way; both ways provide urea, which the microbes digest with their urease.
The use of corn sticks as feed or litter is common, but their use as an organic amendment is also common. The latter is true for two reasons:
it helps to maintain soil health,when maize is grown for grain production (as a grain, as opposed to a silage crop), harvesting maize (grain-free) cane is not economically attractive; there is often no market demand that outweighs its farm value as an organic soil amendment, which in itself represents an economic value. Regular annual harvesting of whole corn plants (silage hash) is more difficult for soil management than corn-cereal cultivation and the use of residues as amendments.
Reintegration of organic matter is good for the soil, although it needs to be managed appropriately to prevent the ” nitrogen starvation ” of the next crop, as a high C / N ratio results in blockage of the soil. available nitrogen by soil micro-organisms that rapidly break down cellulose and lignin. They can outgrow the plants for nitrogen. There are both biological and conventional ways to increase nitrogen inputs, either by adding animal urine and manure in the first case, or commercial fertilizers in the latter; both methods bring urea,urease.
Another use for corn stover is as fuel for bioenergy or as feedstock for bioproducts. It can be burned in furnaces to yield energy that steam turbines convert to electricity. It also has potential for cellulosic ethanol (biomass ethanol), which is “ethanol made from non-grain plant materials known as biomass.” However, with current technology, a large part of the biofuel potential of cellulose is wasted due to the strength of the glycosidic bonds that pair chains of D-glucose units. But if the commercialization 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.” The free accessibility to corn stover makes it a prime candidate for biomass ethanol production. A new DuPont facility in Nevada, Iowa, is expected to generate 30 million gallons annually of cellulosic biofuel produced from corn stover residues. It opened in 2015, with full production provisionally delayed until 2017.
Source from Wikipedia