Agronomy

Summary

Agronomy is the interdisciplinary field in which plant and soil sciences are applied to the production of crops. Agronomists develop ways crop yields can be increased and their quality improved. Some agronomists specialize in soil management and land use, which seeks to protect existing farmland and reclaim land for future use in growing crops. Other specialties cover areas such as weed and pest management, meteorology, and the impact of climate change on crop production. The growing importance of biofuels, such as ethanol, has increased interest in agronomy as a scientific and professional field.

Definition and Basic Principles

Agronomy studies plants grown as crops for food, animal feed, and nonfood uses such as energy. In the United States, these crops include wheat, corn, soybeans, grasses, cotton, and various fruits and vegetables. Leading crops in other countries vary widely, depending on the nature of the local soil, geography, and growing season.

Plant science is a major component of agronomy. Many agronomists look for ways to grow stronger, hardier plants with higher yields. New types of plants are bred by agronomists to contain specific improvements, such as increased nutrient levels or resistance to pests, over earlier breeds. An area of strong interest is the development of plant types that require fewer inputs such as fertilizers and insecticides to perform well.

The field of agronomy also covers the many environmental factors that influence crop success or failure. The chemical makeup and water balance of a crop's soil are leading factors. Weather and climate patterns, both within a single season and over many years, affect the quantity and quality of crop yields. Technology and economics influence demand for certain crop types, pushing market prices up and down. Agronomists help producers respond to these factors.

Background and History

Agronomy is nearly as old as human civilization. According to archaeological findings, people have been growing plants for food for more than ten thousand years, starting in the western Asian regions of what was Mesopotamia and the Levant.

Many historians believe that plant cultivation, the earliest form of farming, led to a major change in human culture. The growing season required people to live in one place for long periods of time. Permanent settlements near fields most likely evolved into some of the first villages. These settlements were often near water sources such as rivers, which were needed to irrigate field crops. Some of the first developments in agronomy involved the design and building of water-delivery systems.

The Industrial Revolution brought widespread change to the field of agronomy. Steam-powered farming equipment replaced draft animals such as horses and mules. Plant scientists developed and standardized new breeds of field crops, which increased yields. By the mid-twentieth century, nearly all corn grown in the United States was from hybrid stock.

The use of inputs such as fertilizers and pesticides also increased but, in some cases, caused significant environmental harm. Since the 1990s, agronomists have focused more closely on improving crops without damaging local ecosystems. In the twenty-first century, technology has placed a critical role in agronomy.

How It Works

Field crops require the right plant type and breed, healthy soil, adequate water and nutrients, appropriate growing temperatures and rainfall, and the control of disease and pests to succeed.

Plant Breeding and Genetics. When choosing a type of field crop to plant, farmers and growers consider factors such as the hardiness of certain breeds and their expected yields at the end of the harvest season. Buyers of agricultural products, such as food-manufacturing companies, look for products that are high in quality and contain specific nutritional or chemical properties. Agronomists specializing in plant breeding and genetics support the needs of both farms and buyers.

Multiple methods are used to create hybrid plants. Some hybrid strains are created by planting one breed next to another and allowing the two breeds to cross-pollinate. Plant scientists also use in vitro techniques, in which plant tissues are combined in a laboratory setting to create strains that would not occur in nature. One technique that has received significant media attention is genetic modification. Genetically modified plants contain genes introduced directly from other sources that create changes in the plant much more quickly than could be generated through traditional breeding.

Soil Health. To support a crop with the highest possible yields, the soil in which the seeds are planted must be in good condition and match the needs of the particular plant breed. The health of soil can be measured on the basis of its physical properties, its chemical makeup, and the biological material it contains. These qualities are tracked by soil surveys that are conducted and published regularly. Farmers may switch the types of crops they grow in a particular field every few years to keep certain soil nutrients from being depleted. This practice is known as crop rotation.

Hydration and Irrigation. Field crops require vast amounts of water. When sources such as rainfall do not provide enough water for healthy plant growth, hydration must be supplemented by irrigation. Irrigation systems are often based on networks of pipes or hoses connected to sprinklers or drip mechanisms that can supply water to an entire field.

Weather and Climate. Even when a hardy breed of plant is grown in healthy soil and receives enough water, unexpected weather patterns can damage or destroy an entire crop. Many farmers and growers protect themselves against weather-related risks by purchasing crop insurance, which covers losses in storms or early freezes. While climate has less variance for individual farmers on a season-by-season basis, changes in climate over the long term can affect the types of plants that grow successfully in a given area. Climate change can often increase or decrease the amount of land suited for growing crops and can have other significant impacts on the health of soil and plants.

Pathology and Pest Control. Like any living organism, field crops are susceptible to natural threats such as disease, predators, and competition from other plants. Agronomists specializing in plant pathology look for ways to fight disease through direct treatment as well as the breeding of new, hardier strains for future crops. Pests such as insects are controlled through applying inputs such as insecticides. Pest control also influences plant genetics, as in the case of cotton bred to contain a natural compound toxic to boll weevils. Weeds are managed through a combination of herbicides, adjustments to soil properties such as adding or removing water and developing plant breeds resistant to weeds.

Applications and Products

Agronomic crops can be broken down into categories in several different ways, such as plant type or climate in which the crop is most likely to be found. One of the most common ways field crops are grouped is by the end use of the raw material. Nearly all crops in the world can be considered a form of food, animal feed, fiber, energy, or tools for environmental preservation. Major crops, such as corn, can be classified in multiple ways, as corn is used for feeding people and animals and is refined into ethanol.

Food. Food represents one of the most diverse categories of agronomic crops in the United States and worldwide. When people think of field crops and food, the types of plants that come to mind first are grains such as corn, wheat, and rice. When measured by acres of land planted, grains make up the largest share of agronomic crops grown worldwide. This category also includes fruits, tree nuts, vegetables, plants grown to be refined into sugar and sweeteners (such as beets and sugarcane), and plants from which oil is made (such as soybeans). While tobacco is not considered a food product, tobacco crops are often included in this category because cigarettes and other items made from tobacco leaves can be consumed only once.

The demand for food crops worldwide grows only as fast as the global population. However, individual types of food crops may face sharp increases and drops in demand. These changes are influenced by weather patterns and crop failures, prices set by the commodities markets (which, in turn, make the prices of consumer items rise and fall), and the changing tastes of food buyers. The spike in popular interest in low-carbohydrate diets in the late 1990s impacted crops used to make products such as flours and sugars. Potato production also took a hit with this food trend. Similarly, populations in developing countries where incomes are rising often change their food-buying habits and choose items more prominent in North American and European diets than in local ones. This pattern can push up prices for crops such as corn and lower demand for locally grown fruits and vegetables. Interestingly, this trend also works in reverse. Consumers in affluent economies such as the United States have become more interested in buying produce from crops grown locally to reduce the overall impact on the environment. These changes can lead to rapid shifts in demand for individual types of agronomic crops.

Animal Feed. As with food, the category of agronomic crops grown for animal feed is dominated by grains. In the United States, the leading feed grains tracked by the US Department of Agriculture (USDA) are corn, sorghum, barley, and oats. Corn makes up the largest share of this category by volume. While the number of farms producing feed grain has decreased in recent years, the number of acres in production has grown. According to the USDA Economic Research Service, US farms have planted at least ninety million acres of corn each year since 2010, much of which was used for animal feed.

A second type of animal-feed crop is hay. Much of the hay grown and harvested in the United States comes from alfalfa plants or a mixture of grass types. Demand for hay is influenced in part by weather. Farmers feed more hay to their livestock—particularly cattle—in drier conditions. Hay is often grouped by the USDA with a type of crop known as silage. Silage is not a unique plant; rather it is the plant stalks and leaves left after the harvesting and processing of grains such as corn and sorghum. Hay and silage together belong to a category of crops known as forage. While forage was once defined as plant matter eaten by livestock grazing in fields, it has been expanded to include plants cut, dried, and brought to the animals.

Fiber. Plants grown for nonfood use often fall into the category of fiber. Fiber crops are processed for making cloth, rope, paper and packaging, and composite materials, such as insulation for homes. In the United States, most of the yearly agronomic fiber crop is made up of cotton plants. In 2023, the United States was the fourth-largest grower of cotton in the world, according to the USDA. Other plants in this category are jute, sisal, and flax. Jute and sisal are frequently used to make rope, burlap, and rugs. Flax is refined into linen and used in various applications ranging from fine clothing and home-decorating products to high-grade papers. Flax fiber is also used in making rope and burlap.

Energy and Environmental Preservation. Most agronomic crops in these categories also appear in one of the three categories above. Of the crops grown in the United States as bioenergy sources, corn tops the list as a source of ethanol. Ethanol sources in other countries include crops such as sugarcane and grasses. Vegetable-based oils made from soybeans are blended into diesel fuel to make a composite known as biodiesel. The refining processes for turning crops into bioenergy sources are not yet as cost-effective as fossil fuels such as petroleum and coal, but this situation may change as technologies improve.

Environmental preservation from the standpoint of agronomic crops is a broad and developing category. It includes strategically planting and rotating crops to return depleted nutrients to the soil. It also allows plants to grow near fields to minimize soil runoff and protect endangered areas such as wetlands.

Careers and Course Work

A career in agronomy requires a solid background in agricultural science. Most agronomists hold bachelor's degrees, while many specialists—particularly those in research or teaching positions—have master's degrees or doctorates. All state colleges and universities established as land-grant institutions offer programs in agronomy or agricultural science as part of their educational mission. These programs allow students to specialize in plant genetics and breeding, soil science, meteorology and climatology, and agronomic finance and business management.

Students majoring in agronomy take courses in a wide variety of areas. Common fields are mathematics (particularly calculus and geometry), physics, and mechanics. Depending on the field a student pursues, advanced coursework in biology, botany and plant science, and organic chemistry may be needed. Many courses are highly focused in scope, such as plant pathology or the physical properties of soil.

Demand for professionals with agronomy degrees is rising, according to the US Department of Labor. Job growth in the field of agricultural and food science was projected to be 9 percent between 2020 and 2030. The need for reliable, efficient, environmentally sound sources of plant-based food is a major factor. The increasing use of biomass energy is also contributing to the need for agronomists with an up-to-date knowledge of science and technology.

Many agronomists work for companies that serve farms. These companies manufacture inputs such as fertilizers, create new breeds of field crops, and process raw materials such as grains and fibers. Other agronomists work for government agencies, primarily within the USDA, or teach and conduct research at colleges and universities. Still others are independent consultants.

Social Context and Future Prospects

One of the turning points in public consciousness about agronomy was the release of Rachel Carson's book Silent Spring in 1962. Carson's book linked several ecological problems, particularly the deaths of wild plants and birds, to the widespread use of pesticides such as dichloro-diphenyl-trichloroethane (DDT). Many of these pesticides were used on field crops. The book led to the United States' ban on DDT in 1972 and increased public awareness of the potential environmental harm of certain farming practices.

Consumer interest in the quality of food sources has risen since the 1990s. While there has been demand for products such as local and organic foods for much of the twentieth century, the category has grown most quickly at the beginning of the twenty-first century. Some consumers participate in community-supported agriculture (CSA) programs in which fruits, vegetables, dairy, and other items are received directly from local farmers. Gourmet and chain restaurants are more likely to advertise their use of locally grown and environmentally sound food ingredients. This demand extends to nonfood items ranging from organic cotton fibers in clothing and linens to plant-based, biodegradable home products. It has also influenced the growth of plant-based, nonpetroleum energy sources such as ethanol.

Agronomists are well-positioned to benefit professionally from these trends. Upcoming issues of interest for agronomists are likely to include the impact of changing weather and climate patterns and ways to increase crop yields without causing environmental harm. Sustainable practices and a focus on global climate change remain at the forefront of agronomy. Promoting efficient use of resources, decreasing food insecurity, and preserving biodiversity are also important issues. As the twenty-first century progressed, agronomists focused on embracing technology, promoting policy, and providing education. 

Bibliography

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