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Agricultural Pesticides
(University of Florida – IFAS)

The federal government has regulated pesticides since the early 1900s.

The use of synthetic pesticides in agriculture is the most widespread method for pest control. “…Farmers spend approximately $4.1 billion on pesticides annually. They justify this high cost by a direct dollar return of from $3 to $5 for every $1 spent on pesticides.” (1991 edition of the Handbook of Pest Management in Agriculture.)

Environmental and human health problems related to the use of synthetic pesticides have created an increasing pressure against their use. In recent years, non-chemical alternatives for pest control have been developed and modern pesticides have become safer and more specific. Technical developments of the application equipment have also improved to enable their proper application. However, their proper professional use has not always been transferred satisfactorily to field practice.

Alternative approaches to pest control are used more and more and the concept of integrated pest management where synthetic pesticides are only applied as a last resort is now considered common practice in professional agriculture. The non-chemical alternatives include cultural practices, choice of resistant varieties, creation of an environment favorable for natural enemies of pests, and use of biological products and agents, including beneficial insects.

Likewise, synthetic pesticides have undergone a development process to match today’s requirements. They have become less toxic for humans, though not necessarily for the environment, they have become more specific to act as a useful contribution within an IPM concept and they have become more powerful. While 40 years ago pesticides were applied in kilograms or liters of active ingredient per hectare, modern pesticides only require grams or milliliters to achieve the same or better result.

On the other hand, the new pesticides require a more sophisticated technology for a safe, even and efficient application. Modern application equipment (including backpack sprayers) allow a fairly safe and efficient application of pesticides of all kinds. “The design of equipment has impact mostly on the operator and environmental safety preventing unnecessary contamination, accidents, loss and spills and allowing an even distribution of the product.” Modern electronics have improved the accuracy of dosing, distribution, and application. The use of global positioning systems (GPS) allows precise tracking of the application. Spray nozzle technology greatly affects spray coverage, which is second in importance only to the selection of the pesticide in determining the success of an application.

Originally, the purpose of pesticide laws and regulations was to protect consumers from fraudulent claims about product performance. The focus now has shifted to the protection of health and the environment, including:

* Providing for the proper and beneficial use of pesticides to protect public health and safety.
* Protecting the environment by controlling the uses and disposal of potentially harmful pesticides.
* Assuring safe working conditions for farm workers, commercial pest control personnel, and consumers.
* Assuring users that pesticides are labeled properly and are appropriate for their intended use, and contain all instructions and precautions necessary.
* Encouraging the use of integrated pest management (IPM) systems that emphasize biological and cultural pest control techniques with selective use of pesticides.

More information on Agricultural Pesticides

* Benefits of Pesticide Use
* Risks of Pesticide Use
* Lethal Dosage (LD50) Values
* Ever-Changing Laws and Regulations
* Formulation Selection Considerations
* Integrated Pest Management
* Water Quality
* Soil/Water Adsorption Coefficient (Kd)
* Water Solubility
* Half-Life
* Movement Off Target

Benefits of Pesticide Use

For many years, we have enjoyed the benefits of using pesticides to control weed, insect, fungus, parasitic, and rodent pests. Recently, both the public and the press have increasingly focused on the negative impacts of agricultural, urban industrial, and residential chemicals. However, there are also substantial benefits to society, including:

* Pesticides are the only effective means of controlling disease organisms, weeds, or insect pests in many circumstances.
* Consumers receive direct benefits from pesticides through wider selections and lower prices for food and clothing.
* Pesticides protect private, public, and commercial dwellings from structural damage associated with termite infestations.
* Pesticides contribute to enhanced human health by preventing disease outbreaks through the control of rodent and insect populations.
* Pesticides are used to sanitize our drinking and recreational water.
* Pesticides are used to disinfect indoor areas (e.g., kitchens, operating rooms, nursing homes) as well as dental and surgical instruments.
* The pesticide industry also provides benefits to society. For instance, local communities and state governments may be partially dependent upon the jobs and tax base that pesticide manufacturers, distributors, dealers, commercial applicators, and farmers provide.

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Risks of Pesticide Use

Within the last few decades, scientists have learned that some pesticides can leach through the soil and enter the groundwater below. While 50% of the nation depends upon groundwater for drinking water, almost 95% of the households in rural areas use groundwater as their primary source of drinking water. The impact of agricultural chemicals on surface and groundwater quality has become an issue of national importance.

EPA has responsibility under a variety of statutes to protect the quality of the nation’s ground water as well as direct responsibility for regulating the availability and use of pesticide products.

Each pesticide product has inherent risks associated with it. Potentially detrimental impacts of pesticides include:

* Acute poisoning from a single or short-term exposure can result in death.
* Chronic impacts of long-term exposure to pesticides, including pesticide residues in food, could also result in death.
* Natural resources can be degraded when pesticide residues in storm water runoff enter streams or leach into groundwater.
* Pesticides that drift from the site of application can harm or kill nontarget plants, birds, fish, or other wildlife.
* The mishandling of pesticides in storage facilities and in mixing and loading areas can contribute to soil and water contamination.

The risk associated with a given pesticide or pesticide product depends on the toxicity of the compound and the probability of exposure.

Source: University of Florida – IFAS

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Lethal Dosage (LD50) Values

An LD50 is a standard measurement of acute toxicity that is stated in milligrams (mg) of pesticide per kilogram (kg) of body weight. An LD50 represents the individual dose required to kill 50 percent of a population of test animals (e.g., rats, fish, mice, cockroaches). Because LD50 values are standard measurements, it is possible to compare relative toxicities among pesticides. The lower the LD50 dose, the more toxic the pesticide.

A pesticide with an LD50 value of 10 mg/kg is 10 times more toxic than a pesticide with an LD50 of 100 mg/kg.

The toxicity of a pesticide is related to the mode of entry of the chemical into an organism. Oral LD50 values are obtained when test subjects are fed pesticide-treated feed or water. Dermal LD50 values are obtained when the pesticide is applied to the skin of the animal. Inhalation LD50 values are obtained when the animal breathes the pesticide with a mask. Often the inhalation LD50 is lower (more toxic) than the oral LD50, which is in turn lower (more toxic) than the dermal LD50.

LD50 values are not always given on the pesticide label; rather, the relative toxicity of a pesticide product is reflected by one of three signal words: DANGER, WARNING, or CAUTION. The purpose of signal words is to alert the user to the level of toxicity of the product. The signal word is generally assigned based on the pesticide’s inhalation, oral or dermal toxicity, whichever is the most toxic.

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Ever-Changing Laws and Regulations

Shortly after the EPA’s Groundwater Protection Strategy was issued in August 1984, the Agency initiated an intensive review of existing information and scientific knowledge about the extent of pesticide contamination, its causes and potential health impacts, and statutory authorities and programs available to help address the problem. EPA supports state strategy development through grants under Section 106 of the Clean Water Act as a means for strengthening the capacity of state governments to protect groundwater quality.

Other regulations and programs such as the Safe Drinking Water Act and its amendments, a new Wellhead Protection Program, Clean Water Act, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and the new Non-point Source Management Program have all been initiated in an attempt to protect the nation’s groundwater from contamination by all types of pollutants including pesticides. Since the early 1970s, the EPA’s Office of Pesticide Programs has been evaluating the leaching potential of new and existing pesticides.

Because of potential environmental concerns associated with pesticide application, there are two federal laws that regulate pesticide use: FIFRA and FFDCA. Most of the states have also enacted their own pesticide legislation. All pesticide labels contain certain standard information, including the ingredients, directions for proper use, warning statements to protect users, the public, and nontarget species of plants and animals. All statements on the label must be adhered to by all users and sellers. All pesticides must be registered with the EPA to ensure that they will not cause unreasonable adverse effects on the environment.

Certain pesticides are classified as “Restricted-Use” and can only be used by or under the direct supervision of a trained Certified Applicator. Restricted-Use pesticides are those that have a greater chance of causing adverse impacts to humans and the environment. Certification is a way of ensuring that people who apply these restricted-use pesticides possess the knowledge to do so in a safe manner. It is illegal to make restricted use pesticides available to non-certified personnel.

The benefits and risks are periodically reassessed as new scientific information is discovered and to reflect changes in the views of society. This does not mean that decisions of today eventually will be proven wrong. Rather, the balance of benefits and risks is ever-changing because of improved science and the changing expectations of society.

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Formulation Selection Considerations

The importance of formulation type is generally overlooked. The decision to use a formulation for a given application should include an analysis of the following factors:

* Applicator safety. Different formulations present various degrees of hazard to the applicator. Some products are easily inhaled, while others readily penetrate skin, or cause injury when splashed in the eyes.
* Environmental concerns. Special precautions need to be taken with formulations that are prone to drift in air or move off-target into water. Wildlife can also be affected to varying degrees by different formulations. Birds may be attracted by granules, and fish or aquatic invertebrates can prove especially sensitive to specific pesticide formulations such as 2,4-D esters.
* Pest biology. The growth habits and survival strategies of a pest will often determine what formulation provides optimum contact between the active ingredient and the pest.
* Available application equipment. Some pesticide formulations require specialized application equipment. This includes safety equipment, spill control equipment and, in special cases, containment structures.
* Surfaces to be protected. Applicators should be aware that certain formulations can stain fabrics, discolor linoleum, dissolve plastic, or burn foliage.
* Cost. Product prices may vary substantially, based on the active ingredients present and the complexity of delivering active ingredients in specific formulations.

Individuals such as commercial pest control technicians or farm workers who may not be involved in the selection process but are responsible for the actual application should also be made aware of the type of formulation they are using, its dangers and of the safety measures needed. This choice of formulation type can have an impact on human health and the environment. Inattention to the type of formulation being used could mean the difference between a routine application and one that is the source of environmental contamination – or worse, a serious human exposure.

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Integrated Pest Management

Integrated pest management (IPM) is the control strategy of choice for homeowners, growers, and commercial applicators. IPM is an approach to pest management that blends all available management techniques – nonchemical and chemical – into one strategy: Monitor pest problems, use nonchemical pest control, and resort to pesticides only when pest damage exceeds an economic or aesthetic threshold.

Labels and regulations change and new products are introduced routinely. Therefore, the pesticide selection process should be conducted just prior to each growing season.

The selection of a pesticide requires planning and knowledge of the alternatives. Begin by developing a comprehensive list of available pesticides for a specific crop, turf, or home garden pest. Pesticide recommendations for controlling any insect, weed, or disease can be suggested by numerous sources: the Cooperative Extension Service; consultants; agrichemical and urban pesticide dealers; product manufacturers; garden and nursery centers; association newsletters; trade journals; and expert applicators. After developing a pesticide list, the user should obtain labels of all products under consideration so that their strengths and weaknesses can be analyzed on a product profile worksheet. Labels generally are available locally from retail outlets or their suppliers.

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Water Quality

Four factors influence groundwater vulnerability to pesticide contamination:

1. Chemical properties of the pesticide
* Low soil adsorption
* Persistence

2. Soil Types
* Sandy or gravel texture
* Low organic matter content

3. Site Characteristics
* Shallow water table
* Sinkholes
* Abandoned wells

4. Management Practices
* Improper chemical storage, handling, and use

Options for protecting surface water near application sites include:

* No-spray strips around surface water supplies, wells, or irrigation ditches
* Grass waterways and grass buffers to resist runoff
* Use of conservation practices on erodible lands
* Plow berms around sinkholes

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Soil/Water Adsorption Coefficient (Kd)

The Kd value is a measure of how tightly the pesticide binds or sticks to soil particles. The greater the Kd value, the less likely a chemical will leach or contribute to runoff. A very high value means it is strongly adsorbed onto soil and organic matter and does not move throughout the soil.

Higher is better. Pesticides are less likely to leach or occur as surface runoff when the Kd is greater than 5.

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Water Solubility

Solubility is a measure of how easily a chemical dissolves in water. The lower a chemical’s solubility, the less likely it is to move with water through the soil.

Lower is better. Pesticides are less likely to leach when their water solubility is less than 30 parts per million.

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Half-life is a measure of how quickly a chemical breaks down in soil (soil half-life) or water (hydrolysis half-life). The longer a chemical remains in water or soil without breaking down, the more likely it is to leach through the soil.

Shorter is better. Pesticides are less likely to leach when their hydrolysis half-life is less than six months and their soil half-life is less than three weeks.

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Movement Off Target

Pesticide particle drift and volatilization pose risks to neighbors, field workers, and the environment. Keeping products on the target site increases the effectiveness of pest control while reducing injury to nontarget susceptible plants, domestic animals, and wildlife. The proximity of an application site to sensitive areas such as nursing homes, subdivisions, schools, day-care centers, parks, playgrounds and hospitals is a critical factor requiring extra safety precautions. Misapplication can endanger public health and violate the law.

Two options exist for the applicator who is concerned about drift:

* Alter routine spray practices
* Switch to products than can be more easily managed to prevent particle drift or volatilization

Management decisions that can help prevent off-target movement include:

* Allowing for buffer zones and planting setbacks
* Incorporating pesticides into the soil
* Slowing the speed of the equipment
* Altering application methods
* Applying sprays nearer the target pest
* Applying at lower pressure
* Altering the time of application.

Products may vary in their ability to move out of the target treatment area. Evaluate each product to determine the best choice for your site requirements.

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Crop Glossary

Acre – The unit of measure most typically used to describe land area in the United States. An acre is equivalent to 43,560 square feet and is about 9/10 the size of a football field.

Acre-Inch – A volume measurement typically associated with irrigation operations on cropland. An acre-inch is equivalent to 27,154 gallons. When an inch of water is applied to cropland via irrigation, each acre receives 27,154 gallons. (Alternatively, a measure of the volume of water applied to the soil/growing crop using irrigation – approximately equivalent to 27,154 gallons.)

Agribusiness – An enterprise that derives a significant portion of its revenues from sales of agricultural products or sales to agricultural producers.

Anhydrous Ammonia – A fertilizer used to provide nitrogen for crop production. The product, stored under high pressure as a liquid, changes state during application and is injected into soil as a gas. It is popular due to the fact that it is composed of 82 percent nitrogen compared to other nitrogen fertilizers such as urea that contain only 46% nitrogen and ammonium nitrate with 30-33% nitrogen content.

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Boot – The time when the head is enclosed by the sheath of the uppermost leaf.

Bt Corn – Field corn that has received a gene transferred from a naturally-occurring soil bacterium called Bacillus thuringiensis. The gene causes the corn plant to produce one of several insecticidal compounds commonly called Bt toxins. The toxins affect the midgut of particular groups of insects such as European corn borer that can be harmful to corn.

Bushel – A unit of dry volume typically used to quantify crop yields. One bushel is equivalent to 32 quarts or 2,150.42 cubic inches. A bushel is often used to represent the weight of a particular crop; for example, one bushel of No. 2 yellow shelled corn at 15.5% moisture content weighs 56 lb.

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Cash Crop – An agricultural crop grown to provide revenue from an off-farm source.

Center Pivot – A type of irrigation system that consists of a wheel-driven frame that supports a series of sprinkler nozzles. The frame rotates about a central point to distribute water over a large circular area.

Channel Erosion – Erosion in channels is mostly caused by downward scour due to flow shear stress. Side wall sluffing can also occur during widening of the channel caused by large flows.

Conservation Tillage – Any tillage and planting system that covers 30 percent or more of the soil surface with crop residue, after planting, to reduce soil erosion by water. Where soil erosion by wind is the primary concern, any system that maintains at least 1,000 pounds per acre of flat, small grain residue equivalent on the surface throughout the critical wind erosion period.

Conventional Tillage – Full width tillage that disturbs the entire soil surface and is performed prior to and/or during planting. There is less than 15 percent residue cover after planting, or less than 500 pounds per acre of small grain residue equivalent throughout the critical wind erosion period. Generally involves plowing or intensive (numerous) tillage trips. Weed control is accomplished with crop protection products and/or row cultivation.

Corn Belt – The area of the United States where corn is a principal cash crop, including Iowa, Indiana, most of Illinois, and parts of Kansas, Missouri, Nebraska, South Dakota, Minnesota, Ohio, and Wisconsin.

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Depression – A low area in a field where surface drainage away from the area does not occur.

Drawbar – A tractor component typically located at the rear and near the ground that permits attachment of implements for pulling or towing.

Drawbar Work – Any operation performed by a tractor that requires force to be exerted by wheels/tracks to propel an implement through or over the soil.

Drilled – Planted with a grain drill. Grain drills differ from row crop planters in that they do not meter individual seeds, but drop small groups of seed in a process referred to as bulk metering. Drills plant crops in closely spaced rows (typically seven to 10 inches on center) that will not be mechanically cultivated.

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Ensiling – The process of creating silage via anaerobic fermentation.

Eutrophication – The process by which lakes and streams are enriched by nutrients (usually phosphorus and nitrogen) which leads to excessive plant growth.

Federal, Food, Drug, and Cosmetic Act (FFDCA) – It specifies the levels of pesticides, chemicals, and naturally occurring poisonous substances in food products. It also regulates the safety of cosmetic products.

Source: University of Vermont Environmental Safety Facility Exit EPA

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) – The objective of FIFRA is to provide federal control of pesticide distribution, sale, and use. All pesticides used in the United States must be registered (licensed) by EPA. Registration assures that pesticides will be properly labeled and that, if used in accordance with specifications, they will not cause unreasonable harm to the environment. Use of each registered pesticide must be consistent with use directions contained on the label or labeling.

Source: EPA’s Agriculture Web site

Feed Grain – Any of a number of grains used for livestock or poultry feed. Corn and sorghum are feed grains.

Flowering – This is the stage when the crop starts flowering. In corn, tassel emergence and pollen shedding takes place at this stage. Two to three days after pollen shedding, silk emergence takes place. At this stage, typically occurs 51-56 days after planting the corn seed, pollination between silks (female) and tassels (male) takes place.

Forage Crop – Annual or perennial crops grown primarily to provide feed for livestock. During harvesting operations, most of the aboveground portion of the plant is removed from the field and processed for later feeding.

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Genetically-Modified Organism (GMO) – A term that refers to plants that have had genes implanted to improve their performance by making them resistant to certain pesticides, diseases, or insects.

Grazing – Any vegetated land that is grazed or that has the potential to be grazed by animals.

Source: Forage Information System Exit EPA

Ground Water – The water under the surface of the earth that is found within the pore spaces and cracks between the particles of soil, sand, gravel and bedrock.

Gully Erosion – They are formed when channel development has progressed to the point where the gully is too wide and too deep to be tilled across. These channels carry large amounts of water after rains and deposit eroded material at the foot of the gully. They disfigure landscape and make land unfit for growing crops.

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Hay – The product of any of a variety of perennial crops, typically grasses or legumes, that can be used a feed for ruminant animals.

Heading – The stage in which the head pushes its way through the flag leaf collar.

IPM – An integrated approach to controlling plant pests using careful monitoring of pests and weeds. It may include use of natural predators, chemical agents and crop rotations.

Source: Pennsylvania Farm Bureau Glossary of Terms Exit EPA

Leach – The downward transport of dissolved or suspended minerals, fertilizers, pesticides and other substances by water percolating through the soil.

Karst – Areas with shallow ground water, caverns, and sinkholes.

Mulch Tillage – Full-width tillage involving one or more tillage trips which disturbs all of the soil surface and is done prior to and/or during planting. Tillage tools such as chisels, field cultivators, disks, sweeps or blades are used. Weed control is accomplished with crop protection products and/or cultivation.

Source: Conservation Technology Information Center (CTIC) Exit EPA

Non-Point Source Management Program – Under the Non-point Source Management Program, states can receive funding to control non-point sources of pollution to protect surface and ground water, including programs to control pesticide contamination of the ground and surface water.

No-Tillage – Crop production system in which the soil is left undisturbed from harvest to planting. At the time of planting, a narrow strip up to 1/3 as wide as the space between planted rows (strips may involve only residue disturbance or may include soil disturbance) is engaged by a specially equipped planter. Planting or drilling is accomplished using disc openers, coulter(s), row cleaners, in-row chisels, or roto-tillers. Weed control is accomplished primarily with crop protection products. Other common terms used to describe No-till include direct seeding, slot planting, zero-till, row-till, and slot-till.

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Pasture (or Pastureland) – Land used primarily for the production of domesticated forage plants for livestock (in contrast to rangeland, where vegetation is naturally-occurring and is dominated by grasses and perhaps shrubs).

Pesticide – A general name for agricultural chemicals that include:

* Herbicide – for the control of weeds and other plants
* Insecticide – for the control of insects
* Fungicide – for the control of fungi
* Nematocide – for the control of parasitic worms
* Rodenticide – for the control of rodents

Postemergence – Refers to the timing of pest control operations. Postemergence operations are accomplished during the period subsequent to the emergence of a crop from the soil and must be completed prior to point at which crop growth stage prohibits in-field travel (unless alternative application means – aerial or irrigation-based – are used).

Power Take-Off (PTO) – A splined shaft that extends from a tractor drive train and is designed to couple with the splined drive shaft of an implement. The connection permits mechanical power to be transmitted from tractor to implement.

Preemergence – Refers to the timing of pest control operations. Preemergence operations are accomplished during the period subsequent to the planting of a crop and prior to the emergence of that crop from the soil.

Preplant – Refers to the timing of pest control operations. Preplant operations are accomplished during the period subsequent to the harvest of one season’s crop and prior to the planting of the next season’s crop.

Primary Tillage – The mechanical manipulation of soil that displaces and shatters soil to reduce soil strength and to bury or mix plant materials and crop chemicals in the tillage layer. Tends to leave a rough soil surface that is smoothed by secondary tillage.

Ridge Tillage – The soil is left undisturbed from harvest to planting except for strips up to 1/3 of the row width. Planting is completed on the ridge and usually involves the removal of the top of the ridge. Planting is completed with sweeps, disk openers, coulters, or row cleaners. Residue is left on the surface between ridges. Weed control is accomplished with crop protection products (frequently banded) and/or cultivation. Ridges are rebuilt during row cultivation.

Source: Conservation Technology Information Center (CTIC) Exit EPA

Rill Erosion – The removal of soil by concentrated water running through little streamlets, or headcuts. Detachment in a rill occurs if the sediment in the flow is below the amount the load can transport and if the flow exceeds the soil’s resistance to detachment. As detachment continues or flow increases, rills will become wider and deeper.

Row Crop – Agricultural crop planted, usually with mechanical planting devices, in individual rows that are spaced to permit machine traffic during the early parts of the growing season

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Safe Drinking Water Act – The objective of the Safe Drinking Water Act is to protect public health by establishing safe limits (based on the quality of water at the tap) for contaminants that may have an adverse effect on human health, and to prevent contamination of surface and ground sources of drinking water.

Secondary Tillage – The mechanical manipulation of soil that follows primary tillage. Performed at shallower depths than primary tillage, secondary tillage can provide additional soil pulverization, crop chemical mixing, soil surface leveling, and firming, and weed control. In conventional tillage systems, the final secondary tillage pass is used to prepare a seedbed.

Seeded – Generic term for introducing seed into the soil-air-water matrix, typically via a mechanized process that will maximize the likelihood of subsequent seed germination and plant growth.

Self-Propelled – A term that is typically applied to farm machines with integral power units that are capable of moving about as well as performing some other simultaneous operation such as harvesting or spraying a crop.

Sidedress – To apply fertilizer to a standing crop, usually by surface application of liquid fertilizer products or subsurface application of liquid or gaseous fertilizers placed near crop rows.

Silage – A feed prepared by chopping green forage (e.g. grass, legumes, field corn) and placing the material in a structure or container designed to exclude air. The material then undergoes fermentation, retarding spoilage. Silage has a water content of between 60 and 80%.

Silking – It is considered the first reproductive stage

Sinkhole – A surface depression caused by a collapse of soil or overlying formation above fractured or cavernous bedrock.

Soil Test – A soil test indicates the availability of nutrients present in the soil and the availability of those nutrients to crops grown there.

Sown – Planted using a broadcast seeding machine that distributes seed upon the soil surface. The seed may then be incorporated into the soil to ensure adequate seed-soil contact for germination.

Strip Tillage – The process in which only a narrow strip of land needed for the crop row is tilled.

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Tasseling – A condition when the tassel-like male flowers emerge.

Tillage – The mechanical manipulation of soil performed to nurture crops. Tillage can be performed to accomplish a number of tasks including: seedbed preparation, weed control, and crop chemical incorporation.

Transgenic Crop – Contains a gene or genes which have been artificially inserted instead of the plant acquiring the gene(s) through pollination. The inserted gene(s) may come from an unrelated plant or from a completely different species.

Urea – A form of nitrogen that converts readily to ammonium.

Value-Added Products – A general term that refers to agricultural products that have increased in value due to processing. Examples include corn oil and soybean meal.

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Major Crops Grown in the United States

In round numbers, U.S. farmers produce about $100 billion worth of crops and about $100 billion worth of livestock each year. Production data from the year 2000 for major agricultural crops grown in this country are highlighted in the following table:
Major agricultural crops produced in the United States in 2000 (excluding root crops, citrus, vegetable, etc).
Crop Harvested Area
(million acres) Cash Receipts from Sales
($ billion)
Corn (grain)





Sorghum (grain)



Corn: The United States is, by far, the largest producer of corn in the world. Corn is grown on over 400,000 U.S. farms. In 2000, the U.S. produced almost ten billion bushels of the world’s total 23 billion bushel crop. Corn grown for grain accounts for almost one quarter of the harvested crop acres in this country. Corn grown for silage accounts for about two percent of the total harvested cropland or about 6 million acres. The amount of land dedicated to corn silage production varies based on growing conditions. In years that produce weather unfavorable to high corn grain yields, corn can be “salvaged” by harvesting the entire plant as silage.

According to the National Corn Growers Association, about eighty percent of all corn grown in the U.S. is consumed by domestic and overseas livestock, poultry, and fish production. The crop is fed as ground grain, silage, high-moisture, and high-oil corn. About 12% of the U.S. corn crop ends up in foods that are either consumed directly (e.g. corn chips) or indirectly (e.g. high fructose corn syrup). It also has a wide array of industrial uses including ethanol, a popular oxygenate in cleaner burning auto fuels.

Soybeans: Approximately 2.8 billion bushels of soybeans were harvested from almost 73 million acres of cropland in the U.S. in 2000. This acreage is roughly equivalent to that of corn grown for grain. Over 350,000 farms in the United States produce soybeans, accounting for over 50% of the world’s soybean production and $6.66 billion in soybean and product exports in 2000. Soybeans represented 56 percent of world oilseed production in 2000.

Soybeans are used to create a variety of products, the most basic of which are soybean oil, meal, and hulls. According to the United Soybean Board, soybean oil, used in both food manufacturing and frying and sautéing, represents approximately 79 percent of all edible oil consumed in the United States. Soybean oil also makes its way into products ranging from anti-corrosion agents to Soy Diesel fuel to waterproof cement. Over 30 million tons of soybean meal are consumed as livestock feed in a year. Even the hulls are used as a component of cattle feed rations.

Hay: Hay production in the United States exceeds 150 million tons per year. Alfalfa is the primary hay crop grown in this country. U.S. hay is produced mainly for domestic consumption although there is a growing export market. According to the National Hay Association, the most common exports are timothy, some alfalfa, sudangrass, and bermudagrass hay. Hay can be packaged in bales or made into cubes or pellets. Hay crops also produce seeds that can be used for planting or as specialized grains.

Wheat: Over 240,000 farms in the United States produce wheat. The U.S. produces about 13% of the world’s wheat and supplies about 25% of the world’s wheat export market. About two-thirds of total U.S. wheat production comes from the Great Plains (from Texas to Montana).

Wheat is classified by time of year planted, hardness, and color (e.g. Hard Red Winter (HRW)). The characteristics of each class of wheat affect milling and baking when used in food products. Of the wheat consumed in the United States, over 70% is used for food products, about 22% is used for animal feed and residuals, and the remainder is used for seed.

Cotton: Fewer than 32,000 farms in the United States produce cotton. Cotton is grown from coast-to-coast, but in only 17 southern states. Farms in those states produce over 20% of the world’s cotton with annual exports of more than $3 billion. The nation’s cotton farmers harvest about 17 million bales or 7.2 billion pounds of cotton each year.

Cotton is used in a number of consumer and industrial products and is also a feed and food ingredient. Over 60% of the annual cotton crop goes into apparel, 28 percent into home furnishings, and 8 percent into industrial products each year. Cottonseed and cottonseed meal are used in feed for livestock, dairy cattle, and poultry. Cottonseed oil is also used for food products such as margarine and salad dressing.

Grain sorghum: In the United States, grain sorghum is used primarily as an animal feed, but is also used in food products and as an industrial feedstock. Industrial products that utilize sorghum include wallboard and biodegradable packaging materials. Worldwide, over half of the sorghum grown is for human consumption.

Some farmers grow sorghum as a hedge against drought. This water-efficient crop is more drought tolerant and requires fewer inputs than corn. Kansas, Texas, Nebraska, Oklahoma, and Missouri produce most of the grain sorghum grown in this country. The U.S. exports almost half of the sorghum it produces and controls 70% to 80% of world sorghum exports.

As much as 12% of domestic sorghum production goes to produce ethanol and its various co-products. With demand for renewable fuel sources increasing, demand for co-products like sorghum-DDG (dry distillers grain) will increase as well due the sorghum’s favorable nutrition profile.

Rice: Just over 9,000 farms produce rice in the United States. Those farms are concentrated in six states: Arkansas, California, Louisiana, Mississippi, Missouri, and Texas. U.S. rice production accounts for just over 1% of the world’s total, but this country is the second leading rice exporter with 18% of the world market.

About 60% of the rice consumed in the U.S. is for direct food use; another 20% goes into processed foods, and most of the rest into beer.

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Crop Production Systems
Major agricultural crops produced in the United States in 2000.
Crop Harvested Area
(million acres) Cash Receipts from Sales ($ billion)
Corn (grain)





Sorghum (grain)



Of the seven crops listed, six are annual crops that must be replanted each year (only hay crops would be left in place from year to year). The process of cultivating crops typically begins with tillage of the soil. Although tillage can serve a number of functions within a crop production system, the most fundamental function is to create conditions that will ensure good contact between seed and soil at the time of seed planting and the ready availability of water to the seed during germination. The degree to which the soil is disturbed by tillage prior to seed planting provides a means of categorizing crop production within a range of tillage systems. These systems range from no-tillage in which there is not soil disturbance in a field except during the process of planting a crop to conventional tillage in which multiple tillage operations can extend over many months and take place before, during, and after planting. Crop production systems that involve pre-plant tillage but maintain residues from a previous crop on the soil surface are referred to as conservation tillage practices.

For the major row crops produced in the United States, farmers use a range of production practices. Conventional tillage (also known as intensive tillage) usually involves a series of field operations that result in a residue-free soil surface at the time a crop is planted. Conventional tillage systems developed in this country to take advantages of the following benefits:

* Creation of a seedbed or root bed
* Control of weeds or the removal of unwanted crop plants
* Incorporation of plant residues into the soil profile
* Incorporation of fertilizers and/or soil-applied pesticides
* Establishment of specific soil surface configurations for planting, irrigating, drainage, and/or harvesting operations

The major disadvantage of conventional tillage is the susceptibility of “unprotected” soil to erosion by water or by wind. Tillage is also energy-intensive, requiring large inputs of machine work and numerous trips across a field during a single growing season. Conventional tillage was “standard operating procedure” in the era before effective chemical weed and pest control strategies were available to farmers.

Concerns about soil erosion led to the development of crop production strategies that retained crop residues on the soil surface. Conservation tillage requires more sophisticated implements that are capable of producing a seedbed while leaving a portion of surface residues undisturbed. Reduced tillage usually leaves 15% to 30% residue coverage on the soil surface. True conservation tillage is any tillage method that leaves at least 30% residue coverage on the soil after a crop has been planted. It can be accomplished through no-till, strip-till, ridge-till, or mulch till practices.

Organic Farming

Organic farming is a small, but growing, segment of U.S. agriculture. USDA estimates the value of retail sales of organic foods at $6 billion in 1999 with about 12,200 organic farmers nationwide, most with small-scale operations. Organic farming encompasses both crop and animal production and is defined as “ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity.”‘Organic’ is a labeling term that denotes products produced under the authority of the U.S. Organic Foods Production Act. “The principal guidelines are to use materials and practices that enhance the ecological balance of natural systems. Organic agriculture practices do not ensure that products are completely free of residues; however, methods must be used to minimize contamination.” Organic food handlers, processors and retailers must adhere to standards that maintain the integrity of organic agricultural products. This includes practices such as minimizing or eliminating the use of herbicides in crop production and antibiotics in animal production.

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* Operations and Timing
* Equipment Used
* Potential Environmental Problems
* Best Management Practices

Operations and Timing

Most crops in the U.S. are planted in the spring. The exception is winter wheat, which is planted across the U.S. but concentrated in the central and southern Great Plains and the Pacific Northwest. Winter wheat is planted in the fall, goes into dormancy during the winter, and is harvested for grain the following spring.

The table below shows the “usual planting dates” for six major crops. Planting dates vary by region, following the weather. For simplification, the usual range of planting dates for the top-producing states are shown; if planting dates vary widely, more than one is given. The actual planting dates may begin earlier and extend later, but these are considered the most common.

Source: USDA NASS Agricultural Handbook 628 “Usual Planting and Harvesting Dates for U.S. Field Crops” (PDF) (51 pp, 441K, About PDF)

Crop Usual Planting Dates (most active period) in Top-Producing States Top Producing States Total Acreage (million acres)
Barley Apr 7- May 5 (ID); May 2-15 (ND) ND, ID
Corn (grain) April 30-May 18 IA, IL
Hay, alfalfa NA CA, SD
Wheat (spring) May 1-19 ND
Soybeans May15-June 5 IA, IL, MN
Wheat (winter) Sept. 20-Oct. 10 KS

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Equipment Used
Grain Drill

A grain drill on display at a farm machinery show
Source: Daniel R. Ess, Purdue University

Drills – are implements used to plant crops in closely spaced rows (typically four to ten inches); drills are commonly used for cereal crops such as wheat and can be used to plant soybeans. Grain drills are typically equipped with disks to open a small trench in the soil, a metering system to deliver a measured, controlled amount of seed to drop tubes which guide the seed to the seed trench. There must be some means (wheels or drag chains) of gently closing the seed trench with soil to cover the seeds.

A Grain Drill Planting a Crop

A grain drill on planting a crop


Farm tractor and tillage implementation
Source: Daniel R. Ess, Purdue University

Tractors – are traction machines that provide mechanical, hydraulic, and/or electrical power to implements to perform a wide range of crop production and handling operations. Tractors are most often used to perform drawbar work and PTO (power take-off) work. Tractors can be equipped with rubber tires, rubber belts, or steel tracks. A modern farm tractor is almost always equipped with a diesel engine and tractor size is measured by the amount of power that the tractor can produce at the PTO. Tractor sizes range for those with less than 40 PTO horsepower to ones that produce more than 400 horsepower. The cost of a large tractor can exceed $200,000.

Twelve-Row Planter

A twelve-row planter working in a conventionally-tilled field
Source: Source: Daniel R. Ess, Purdue University

Planters – are implements used to plant row crops (typically in row spacings ranging from 10 to 40 inches). Planters open a seed trench, meter seeds one-at-a-time, drop seeds into the seed trench, and gently cover the seed. Some planters can cut through residues and till a small strip of soil in each row at the time of planting. Planters can also be equipped to apply fertilizer, pesticides, and herbicides during planting. Planters come in sizes as large as sixty feet wide – that is twenty-four rows with a typical 30-inch row spacing, or thirty-six rows with a narrower 20-inch row spacing. Such large planters can cost in excess of $100,000.

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Potential Environmental Concerns

One current controversy related to planting is the choice of seeds. More and more of the seeds planted in the U.S. are genetically modified (GMOs) to make crop production more efficient, to better withstand environmental stresses such as drought, flood, frost, or extreme temperatures, to protect crops against pests such as weeds, insects, or diseases, and to be resistant to herbicides. In 1999, 25% of corn and 54% of soybeans planted in the U.S. were genetically modified.

Environmental concerns related to GMOs include increased pest resistance, development of weed tolerance, and decreased genetic diversity. For example, insects exposed to a genetically engineered crop with the Bt gene (Bt is a natural toxin taken from the Bacillus thuringiensis bacteria, which is toxic to a number of insects) may become more resistant to pesticides. This is a serious concern for organic farmers who use Bt on their crops as an alternative to chemical insecticides. Another environmental concern is that, over time, some weed species could develop a tolerance to herbicides that are applied repeatedly to a crop tolerant to that herbicide. A transgenic crop might cross with another crop or weed, resulting in an undesirable crop or weed species. Others are concerned that reliance on a few genetically modified crops may reduce biological diversity. Also, a lack of genetic diversity in the food supply could increase the risk of catastrophic crop failure and threaten our food security.

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Best Management Practices

To reduce the risk of insect resistance to Bt, a certain percentage of crop acreage on every farm is normally devoted to non-genetically modified variety.

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