1.11 Intercropping
1.12 Field Crop Uses
1.2 Agriculture
1.3 Crops
1.4 Field Crops
1.5 High Production Crops
1.6 Field Crop Production Practices_Row Crops
1.7 Cover Crops
1.8 Cover Crop Benefits
1.9 Cover Crop Risks
1_Field-Crops
Field Crops
Overview
Title Image “Line of crops near Littleport; Cambridgeshire” by Keith Evans is licensed under CC BY-SA 2.0
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Introduction
Lesson Objectives
Identify examples of field crops.
Select examples of common field crops from the list provided.
Identify common uses of field crops.
Select common uses of field crops from the list provided.
Explain common production practices for field crops.
Describe common field crop production practices.
Evaluate the economic impact of field crops.
Key Terms
animal feed - the hull and bran from grain that is fed to livestock
cereals - grass grown for the edible component of its grain
corn syrup - refined starch slurry
crop - plants that are cultivated either for sale or for subsistence
crop rotation - growing different crops in the same area in different seasons
field crops - plants grown commercially in large areas
grain - small, dry seed that is harvested for human or animal consumption
intercropping - growing different crops together for mutual benefits
oats - grain grown in cool climates, widely used for human and animal consumption
oil - fat extracted from some plant seeds, fruits and mesocarps
oil crops - plants grown for the oil they produce
row crop - crops planted in rows wide enough for machinery access
silage - anaerobically (without oxygen) fermented corn stalks and other green plants
sweeteners - sugar that provides humans and animals energy in the form of carbohydrates
Introduction
Plants are grown and harvested, from personal use to large scale operations that cover millions of acres. Understanding plants, their uses, and how they are grown are important aspects of agriculture. Supporting American diets and some of those abroad, United States farmers are tasked with producing a large number of crops. Crops extend beyond the monumental task of feeding humans and animals; their fibers and oils are also used in paper, clothing, rope, biofuels and other valuable materials.
Agriculture
Tremendous natural variations exist among the individuals of any plant species. The traits that define color, shape, flavor, height, yield, and resistance to pests, pathogens, and environmental stresses are not fixed within a species. Individual plants and animals from the same species can be easily distinguished based on these characteristics.
Since the beginning of agriculture, humans hve unconsciously been selecting plants and animals with desirable traits, such as large-sized grains, pods, fruits, and vegetables; sweeter and less-seeded fruits; less bitter and nonprickly vegetables; cereals with large panicles and tough rachis; and non-seed-shattering plants. As a consequence of such artificial selections over many generations, unprecedented changes occurred in cultivated plants that set them apart from their ancestors and wild relatives. For example, the relentless efforts of humans led to the development of various crops, such as corn from a wild-grass teosinte; long-spiked, six-row barley from short-spiked, two-row wild barley; large tomatoes from a small berry; and a variety of less-seeded fruits and palatable vegetables from their bitter wild ancestors (see Figure 5.1.1). These plants—enriched in traits that favor higher yields, productive harvest, and increased palatability—would not have come into being without the persistence of humans since the dawn of agriculture.
For several millennia, humans have put tremendous effort into providing protection and ensuring the continuous propagation of cultivated plants. We provide fertilizers, pesticides, and water, as well as provide services such as weeding to promote the growth of crop plants. Thus, domesticated plants need humans for their survival as much as human survival depends on them. These species cannot survive in nature for a long time by themselves, but they have spread globally with human help.
For some species, this dependency on humans has become total. For example, maize absolutely depends on humans for its survival. If you leave a mature cob in the field, some of its seeds may germinate on the cob, but they will soon die due to the lack of space for emerging seedlings to grow. Furthermore, maize seeds do not fall spontaneously and need human help to be detached from the cob and planted in the soil. This mutual interdependence between crop plants and humans was achieved over several millennia, and this is the historical process known as domestication.
Crops
There are many definitions of the word “crop”. When referring to plants, the United States Department of Agriculture considers crops to be those plants that are cultivated either for sale or for subsistence. There are many plants that are specialty crops when cultivated, but are also collected from wild populations. Wild plants are not considered specialty crops even though they may be used for the same purpose as cultivated plants. This is somewhat common among medicinal herbs and woodland plants. There are a number of native ferns that are collected from wild populations for use in the floral trade. There are also a number of marine plants that are collected from wild populations both for direct consumption and for industrial uses. Although these are specialty uses, wild plants are not considered specialty crops by USDA. However, natural populations of native plants that are brought into cultivation, such as sugar maple trees, pecans, blueberry, huckleberry and cranberry are considered specialty crops by USDA.
In order for a plant to be considered cultivated, some form of management must be applied. The intensity of the management is not critical to determining whether a plant is cultivated or not. This definition includes plants or plant products harvested from “wild areas” whose populations are managed, monitored and documented to ensure long-term, sustainable production. If a naturally occurring population of plants is brought under management and that plant satisfies the definition of specialty crop, then those plants would be considered specialty crops; however, it is common for such plants to be designated “wild-harvested” for marketing purposes. For the purpose of some programs in which state agencies are the eligible entities, states may choose to define plants collected from the wild as specialty crops.
The classifications of cultivated and wild-harvested may both apply to one kind of plant, but the final designation will be determined by how it is grown and what for. For instance, amaranth may be grown as a leafy green, or it may be grown as a grain. Leafy greens are vegetables; therefore, amaranth grown in such a manner would be considered a specialty crop. However, grains are not specialty crops; therefore, amaranth grown for grain would not be considered a specialty crop.
Field Crops
A large majority of agricultural acreage and crop revenue is dedicated to growing plants commercially in large areas: creating field crops. Field crops include but are not limited to corn, cotton, oats, rice, sorghum, soybeans, winter wheat, durum wheat, and spring wheat (Figure 5.1.2). In 2021, corn, soybeans, and all kinds of both wheat and cotton covered 238.7 million acres in the United States, which is about 12.5% of the country’s total area (USDA Acreage Report, 2021).
Many field crops are harvested for grain (Figure 5.1.3). Grain is a small, dry seed that is used for human or animal consumption. Grass grown for the edible component of its grain is known as cereal. Wheat is the most important kind of grain grown in temperate countries, as it is used to make flour for staple foods, such as bread and pasta.
There are differences between whole grains and refined grains. A whole grain consists of the entire grain seed of a plant. This seed, also known as the kernel, is made up of three key parts: the bran, the germ, and the endosperm, as shown in Figure 5.1.4. Whole grains can be eaten whole, cracked, split, flaked, or ground. Most often they are milled into flour and used to make breads, cereals, pasta, crackers, and other grain‐based foods. Refining typically removes the bran and the germ, leaving only the endosperm. Without the bran and germ, about 25% of the grain’s protein is lost, along with at least seventeen key nutrients. Refined products still contribute valuable nutrients because processors add back some vitamins and minerals to enrich refined grains. But whole grains still provide more protein, more fiber, and many other important vitamins and minerals.
High Production Crops
High Production Crops
About a third of America’s corn crop is used for feeding cattle, hogs, and poultry in the U.S. Corn provides the “carbs” in animal feed, while soybeans provide the protein. It takes a couple of bushels of American corn to make corn-fed steak; by some estimates, a beef cow can eat a ton of corn if raised in a feedlot. Both dairy cows and beef cows also consume silage, which is fermented corn stalks and other green plants.
Corn has hundreds of uses. It is used to make breakfast cereal, tortilla chips, grits, canned beer, soda, cooking oil, and bio-degradable packing materials. It’s the key ingredient in the growing medium for life-saving medicines including penicillin. Corn gluten meal is used on flower beds to prevent weeds. Just over a third of the corn crop is used to make ethanol, which serves as a renewable fuel additive to gasoline. The Renewable Fuel Standard requires that 10% of gasoline be renewable fuel, but you can find E15 (15 percent ethanol) or E85 (85 percent) ethanol in some areas, particularly in the Midwest. The rest of the corn crop is used for human food, beverages, and industrial uses in the U.S., or exported to other countries for food or feed use.
Field Crop Production Practices: Row Crops
Row Crop
A row crop is a crop that can be planted in rows wide enough to allow it to be tilled or otherwise cultivated by agricultural machinery—machinery tailored for the seasonal activities of row crops. Such crops are sown by drilling rather than broadcasting; this distinction is significant in crop rotation strategies, where land is planted with row crops, commodity food grains, and sod-forming crops in a sequence meant to protect the quality of the soil while maximizing the soil's annual productivity.
Strategic agricultural planning takes many factors such as water availability and soil quality into consideration. As much as 20% of crops worldwide are irrigated, with some crops such as rice and maize benefiting from the extra water. During the growing season, the inter-row spaces are hoed two to four times and the rows are weeded to conserve moisture and improve aeration. As a result, the soil’s microbiological activity increases and mobilization of nutrients is intensified. Row crops are valuable precursors of spring grain crops, flax, and hemp. The beneficial effect of row crops extends to the second crop. Examples of row crops include sunflower, potato, canola, dry bean, field pea, flax, safflower, buckwheat, cotton, maize, soybeans, and sugar beets.
Cover Crops
The harvest of low residue row crops, such as corn silage or soybeans, usually means the soil surface of a field will be left bare until the next crop is planted, when a new plant canopy is established. In the Northeast, the next planting may be 5-7 months away. That's a long time for the bare soil to be subjected to erosion caused by rainfall, snowmelt, or wind. For that reason, cover crops are usually established in the fall months and remain during the winter. Properly planned and executed, cover crops will protect farmland during this vulnerable period. In the spring they are then killed and left on the surface as residue for conservation tillage or are incorporated into the soil. There are, of course, risks and benefits associated with cover crops. Cover crop species and management should be planned objectively regarding soil erosion, water quality, nutrient management, forage and/or soil quality.
Cover Crop Benefits
The protective canopy formed by a cover crop reduces the impact of rain drops on the soil surface, thereby decreasing the breakdown of soils aggregates. This greatly reduces soil erosion and runoff, and increases infiltration. Decreased soil loss and runoff translates to reduced transport of valuable nutrients, pesticides, herbicides, and harmful pathogens associated with manure from farmland that degrade the quality of bodies of water and pose a threat to human health.
A cover crop slows the velocity of runoff from rainfall and snowmelt, reducing soil loss due to sheet and rill erosion. Over time, a cover crop regimen will increase soil organic matter, leading to improvements in soil structure, stability, and increased moisture and nutrient holding capacity for plant growth. These properties will reduce runoff through improved infiltration (movement of water through the soil surface) and percolation (movement of water through the soil profile). A cover crop will increase soil quality by improving the biological, chemical, and physical soil properties.
As a “trap crop”, a cover crop will store nutrients from manure, mineralized organic nitrogen, or underutilized fertilizer until the following years’ crop can utilize them, reducing nutrient runoff and leaching. When a cover crop is managed for its contribution to soil nitrogen, the application of a nitrogen fertilizer for the subsequent crop may be less, thereby lowering costs of production, reducing nitrogen losses to the environment, and decreasing the need for purchased nitrogen fertilizer that is produced using fossil fuels. Cover crops will reduce or mitigate soil compaction. Deep tap roots of some cover crops grown in the fall and spring, when compacted layers are relatively soft, can penetrate these layers.
Cover crops result in better tillage and traffic conditions by reducing soil moisture deeper into soil profile through evapotranspiration. Improved soil structure and stability can improve the soil’s capacity to withstand heavy farm equipment, resulting in less subsurface compaction. A cover crop provides a natural means of suppressing soil diseases and pests. It can also serve as a mulch or cover to assist in suppressing weed growth. A cover crop can provide high-quality material for grazing livestock and can provide food and habitat for wildlife, beneficial insects, and pollinators.
Cover Crop Risks
While proper planning and management of a cover crop can help minimize or eliminate risks, planting a cover crop does involve some risks and potential drawbacks. Fields with heavy plant residues or early season cover crop weeds or growth are more susceptible to increases in populations of soil insects such as cut worms, army worms, and slugs; however, proper pest scouting and treatment, if needed, can reduce the risk of damage by pests.
Growing the wrong cover crop with inadequate rotations may create problem with diseases because the cover crop may increase the occurrence of a disease in the subsequent crop if it happens to be a host for the organism that causes the disease. For example, the use of a brassica cover crop such as a forage turnip may harbor insects and diseases for a brassica crop like broccoli. Therefore, the choice and management of cover crops should be made with existing weed, disease, nematodes, and other soil problems in mind. Some cover crops need to be terminated early to prevent management problems with soil fertility, over mature cereal rye with increased Carbon Nitrogen ratio (C:N) will tie up nitrogen needed for early corn growth.
The cost of establishing and maintaining a cover crop may outweigh some of the benefits. The added cost of seed, planting, management, disking and incorporating the cover crop, and the possibility of planting delays, may make cover crops unfeasible for some farmers.
Crop Rotation
Most corn and soybeans are grown in rotation with other row crops, while most cotton is grown successively in the same fields. The most common wheat rotation includes fallow or idle land. Soil conserving crops in rotation with corn are more commonly used on highly erodible land (HEL) than on non-HEL.
Intercropping
Incorporating intercropping (growing different crops together) principles into an agricultural operation increases diversity and interaction between plants, arthropods, mammals, birds, and microorganisms resulting in a more stable crop-ecosystem and a more efficient use of space, water, sunlight and nutrients. Furthermore, soil health is benefited by increasing ground coverage with living vegetation, which reduces erosion, as well as by increasing the quantity and diversity of root exudates, which enhance soil fauna. This collaborative type of crop management mimics nature and is subject to fewer pest outbreaks, improved nutrient cycling and crop nutrient uptake, and increased water infiltration and moisture retention. Soil quality, water quality and wildlife habitat all benefit.
Relay, row and strip are three types of intercropping strategies.
- Relay intercropping: growing two or more crops on the same field with the planting of the second crop after the first one (e.g., over seeding of a clover cover crop into cotton during defoliation; planting of clover at lay by time in corn).
- Row intercropping: growing two or more crops simultaneously in the same field with at least one crop planted in rows (e.g., planting corn in the rows and interseeding sorghum between the rows, harvesting all as silage; plant vegetables, cereal grains, perennial covers or annual covers between orchard tree rows).
- Strip intercropping: growing crops in alternate strips wide enough to permit separate crop production machinery, but close enough for crops to interact (e.g., planting alternating strips of corn and soybeans 6 rows each or alternating strips of corn and Sudan grass). Generally, the maximum width of individual strips for effective interaction of crop pests and their natural enemies is about 30 ft.
Field Crop Uses
The corn refining industry produces hundreds of products and byproducts, such as high fructose corn syrup (HFCS), corn syrup, starches, animal feed, oil, and alcohol.
Modified starches are manufactured for various food and trade industries for which unmodified starches are not suitable. For example, large quantities of modified starches go into the manufacture of paper products as binding for the fiber. Modifying is accomplished in tanks that treat the starch slurry with selected chemicals, such as hydrochloric acid, to produce acid-modified starch; sodium hypochlorite, to produce oxidized starch; and ethylene oxide, to produce hydroxyethyl starches. The treated starch is then washed, dried, and packaged for distribution.
Across the corn wet milling industry, about 80 percent of starch slurry goes to corn syrup, sugar, and alcohol production. The relative amounts of starch slurry used for corn syrup, sugar, and alcohol production vary widely among plants. Syrups and sugars are sweeteners formed by hydrolyzing the starch, with partial hydrolysis resulting in corn syrup, and complete hydrolysis producing corn sugar. The hydrolysis step can be accomplished using mineral acids, enzymes, or a combination of both. The hydrolyzed product is then refined, which is the decolorization with activated carbon and the removal of inorganic salt impurities with ion exchange resins. The refined syrup is concentrated to the desired level in evaporators and is cooled for storage and shipping.
Dextrose production is quite similar to corn syrup production, the major difference being that the hydrolysis process is allowed to go to completion. The hydrolyzed liquor is refined with activated carbon and ion exchange resins, to remove color and inorganic salts, and the product stream is concentrated by evaporation to the 70 to 75 percent solids range. After cooling, the liquor is transferred to crystallizing vessels, where it is seeded with sugar crystals from previous batches. The solution is held for several days while the contents are further cooled and the dextrose crystallizes. After about 60 percent of the dextrose solids crystallize, they are removed from the liquid by centrifuges, are dried, and are packed for shipment.
A smaller portion of the syrup refinery is devoted to the production of corn syrup solids. In this operation, refined corn syrup is further concentrated by evaporation to a high dry substance level. The syrup is then solidified by rapid cooling and subsequently milled to form an amorphous crystalline product. Ethanol is produced by the addition of enzymes to the pure starch slurry to hydrolyze the starch to fermentable sugars. Following hydrolysis, yeast is added to initiate the fermentation process. After about 2 days, approximately 90 percent of the starch is converted to ethanol. The fermentation broth is transferred to a still where the ethanol (about 50 vol%) is distilled. Subsequent distillation and treatment steps produce 95 percent, absolute, or denatured ethanol.
The object of silage making is to preserve the harvested crop by anaerobic (without oxygen) fermentation. This process uses bacteria to convert soluble carbohydrates into acetic and lactic acid, which "pickles" the crop. In a well-sealed silo, it can be stored for long periods of time without losing quality. To produce high-quality corn silage, it is important to do a good job in growing, harvesting and preserving the crop. Corn silage is a high-quality forage crop that is used on many dairy farms and on some beef cattle farms in Tennessee. Its popularity is due to the high yield of a very digestible, high-energy crop, and the ease of adapting it to mechanized harvesting and feeding. Corn for silage fits ideally into no-till and double-cropping programs.
Oil-bearing crops or oil crops include both annual (usually called oilseeds) and perennial plants whose seeds, fruits or mesocarp, and nuts are valued mainly for the edible or industrial oils that are extracted from them. Some of the crops included in this chapter are also fiber crops in that both the seeds and the fibers are harvested from the same plant. Such crops include: coconuts, yielding coir from the mesocarp; kapok fruit; seed cotton; linseed; and hempseed. In the case of several other crops, both the pulp of the fruit and the kernels are used for oil. The main crops of this type are oil-palm fruit and tallow tree seeds. Only 5-6 percent of the world production of oil crops is used for seed (oilseeds) and animal feed, while about 8 percent is used for food. Edible processed products from oil crops, other than oil, include flour, flakes or grits, groundnut preparations (butter, salted nuts, candy), preserved olives, desiccated coconut and fermented and non-fermented soya products. The remaining 86 percent is processed into oil.
The fat content of oil crops varies widely. Fat content ranges from as low as 10-15 percent of the weight of coconuts to over 50 percent of the weight of sesame seeds and palm kernels. Carbohydrates, mainly polysaccharides, range from 15 to 30 percent in the oilseeds, but are generally lower in other oil-bearing crops. The protein content is very high in soybeans, at up to 40 percent, but is much lower in many other oilseeds, at 15-25 percent, and is lower still in some other oil-bearing crops. The major U.S. oilseed crops are soybeans, cottonseed, sunflower seed, canola, rapeseed, and peanuts. Soybeans are the dominant oilseed in the United States, accounting for about 90 percent of U.S. oilseed production.
Dig Deeper
Attributions
Title Image “Line of crops near Littleport; Cambridgeshire” by Keith Evans is licensed under CC BY-SA 2.0
"4.2 Crop Rotations" by the United States Department of Agriculture is in the Public Domain.
by the United States Department of Agriculture is in the Public Domain.
"Acreage Report" by the United States Department of Agriculture is in the Public Domain.
"Corn and Other Feedgrains" by the United States Department of Agriculture is in the Public Domain.
"Corn is America's Largest Crop in 2019" by the United States Department of Agriculture is in the Public Domain.
"Cover Crops - Keeping Soil in Place While Providing Other Benefits" by the United States Department of Agriculture Natural Resources Conservation Service is in the Public Domain.
"Definition of Specialty Crop" by the United States Department of Agriculture is in the Public Domain.
"Field Crops" by the United States Department of Agriculture is in the Public Domain.
“Intercropping to Improve Soil Quality and Increase Biodiversity” by the United States Department of Agriculture is in the Public Domain.
"Oil Crops at a Glance" by Mark Ash and Todd Hubbs, United States Department of Agriculture is in the Public Domain.
"Row Crop" by Wikipedia is licensed CC BY-SA.
"SP434D Corn Silage," The University of Tennessee Agricultural Extension Service, SP434D-5M-9/98 E12-2015-00-082-99, used with permission.
"Whole Grains" is licensed under CC BY 4.0.