Introduction to agricultural systems


Industrialized Agriculture in the United States

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Industrialized Agriculture in the United States Since 1940, U.S. farmers have more than doubled crop production while cultivating about the same amount of land. They have done this through industrialized agriculture coupled with a favorable climate and fer­tile soil. They have increased crop yields per acre by massive inputs of fossil fuel energy, irrigation water, commercial inorganic fertilizers, and pesticides.

Less than 1% of the U.S. work force is engaged in farming. Yet the country's 2.1 million farmersCwith only 650,000 working full time at farmingCproduce enough food to feed most of their. fellow citizens better and at a lower percentage of their income than do farmers in any other country. Americans spend an average of 11% to 15% of their disposable income on food, while people in much of the world spend 40% or more. In addition, U.S. farmers produce large amounts of food for export to other countries.


About 23 million peopleC20% of the U.S. work forceCare involved in the U.S. agricultural system in activities ranging from growing and processing food to selling it at the supermarket. In terms of total annual sales, the agricultural system is the biggest industry in the United StatesCbigger than the automotive, steel, and housing industries combined. In 1987, however, farmers got an average of only 25 cents of every dollar spent on food in the United States.

The gigantic agricultural system consumes about 17% of all commercial energy used in the United States each year. Most of this energy comes from oil. Most plant crops in the United States provide more food energy than the energy (mostly from fossil fuels) used to grow them. But raising animals for food requires much more fossil fuel energy than the ani­mals provide as food energy.

Energy efficiency is much worse if we look at the entire U.S. food system. Counting fossil fuel energy inputs used to grow, store, process, package, trans­port, refrigerate, and cook all plant and animal food, ant average of about ten units of nonrenewable fossil fuel energy is needed to put one unit of food energy on the tableC an energy loss of nine units per unit of food energy produced. By comparison, every unit of energy from the human labor of subsistence farmers may provide ten units of food energy.

Suppose everyone in the world ate a typical Amer­ican diet with the food produced by industrialized agriculture. If the world's known oil reserves were used only for producing this food, these reserves would be depleted in 12 years.

Suppose that fossil fuel, especially oil, suddenly becomes and remains scarce or much more expensive, as most energy experts believe will happen sometime between 1995 and 2010. The present industrialized agricultural system in MDCs would collapse, with a sharp drop in world food production and a rise in food prices, malnutrition, and famine.


Examples of Subsistence Agriculture Farmers in LDCs use various forms of subsistence agriculture to grow crops on about 60% of the world's cultivated land. Many subsistence farmers imitate nature by simultaneously growing a variety of crops on the same plot. This biological diversity reduces their chances of losing most or all of their year's food supply from pests, flooding, drought, or other disasters.

Common planting strategies include:



  1. Polyvarietal cultivation, in which a plot of land is planted with several varieties of the same crop.

  2. Intercropping, in which two or several different crops are grown at the same time on a plotCfor example, a carbohydrate-rich grain that depletes soil nitrogen and a protein-rich legume that adds nitrogen to the soil.

  3. Agroforestry, a variation of intercropping in which crops and trees are planted together. For example, a grain or legume crop might be planted around fruit-bearing orchard trees or in rows between fast-growing trees that can be used for fuelwood or to add nitrogen to the soil.

  4. Polyculture, a more complex form of intercrop­ping in which a large number of different plants maturing at different times are planted together (see Case Study below).




Perhaps the most impressive success in food pro­duction has taken place in China. It is able to feed its people by supplementing labor-intensive subsistence agriculture with several forms of modern agricultural technology.

CASE STUDY: Small-scale, ecologically sustainable polyculture in the Philippines.


In parts of the Philippines many : subsistence-farming families use small-scale polyculture to feed themselves. Typically, they harvest crops throughout the year by plant­ing a 0.1-acre plot with a mixture of fast-maturing grains and vegeta­bles, slow-maturing perennials such as papaya and bananas, and slow-maturing tubers such as cas­sava, taro, and sweet potatoes. The diverse root systems at different depths beneath the ground capture soil nutrients and soil moisture efficiently and reduce the need for supplemental organic fer­tilizer (typically home-generated chicken manure) and irrigation ' water. Year-round coverage with plants also protects the soil from wind and water erosion.

The diversity of habitats for nat­ural predators means that crops don't need to be sprayed with insecticides to control pests. Weed­ing is reduced and herbicides are unnecessary because weeds have difficulty in competing for plant nutrients with the multitude of crop plants. The various crops are harvested ­all year, so there is always something to eat or sell. Crop diversity

also provides insurance against unexpected weather changes. If one crop fails because of too much. or too little rain, another crop may survive or even thrive. This approach also spreads the need for labor throughout the growing season.

Most of the crops produced in this particular system have little market value because they are high in starch and low in protein. Nevertheless, using their own hand labor, a typical Filipino farming family can supply most of the food they need with this system. Yields can vary with site, weather, crop combinations, and management. But measurements revealed that the total yield per year on one family's typical polyculture plot was 26 times that of­ nearby Philippine fields planted

the same year with high-yield, hybrid varieties of rice and using large amounts of irrigation water, commercial inorganic fertilizer, insecticides, herbicides, mecha­nized equipment, fossil fuels, and borrowed money. The polyculture plot needed none of these inputs, and the family did not have to bor­row any money. Although small-scale farmers using mechanized, green revolution agriculture can sell their crops, many of them have such large debts that they go bankrupt. They then lose their land and can no longer feed their families by farming. Between 1966 and 1974, for example, the number of land­less rural households in the Philipinines increased from 30 to 45% of the total population

3.10.2 Major world food problems

The Good News About Food Production World food production increased by 140% between 1950 and 1988 and kept ahead of the rate of population growth on all continents except Africa and Latin America. As a result, average food production per person increased by more than 25% between 1950 and 1988, even though world population increased by nearly 2 billion.

During the same period, average food prices adjusted for inflation dropped by 25%, and the amount of food traded in the world market quadrupled. Mos of the increase in food production since 1950 cam' from increases in crop yields per acre by means o improved labor-intensive subsistence agriculture it LDCs and energy-intensive industrialized agriculture in North America, Europe, Australia, New Zealand and parts of Asia.


The Bad News About Food Production The impressive increases in world food production disguise the fact that average food production per person decliner between 1950 and 1988 in 43 LDCs (22 in Africa) containing 1 of every 7 people on earth. The largest decline' have occurred in Africa, where average food production per person dropped 21% between 1960 and 1988 and is projected to drop another 30% during the next 25 years.

When China, which produces 35% of the world" food, is removed from the calculation, food production gains in most other LDCs since 1950 barely matcher their population growth. Average per capita food pro auction has been falling in Africa since 1967 and ir Latin America since 1982.

Another disturbing trend is that the rate of increase in world average food production per person has been steadily declining during each of the past three dec­ades. It rose 15% between 1950 and 1960, 7% between 1960 and 1970, and only 4% between 1970 and 1980. Between 1985 and 1988, average per capita food pro­duction fell. This trend is caused by a combination of population increase, a decrease in yields per unit of land area for some crops cultivated by industrialized agriculture, sharp drops in food production in some countries, and widespread drought in 1987 and 1988.

According to the UN Food and Agriculture Orga­nization, failure to increase crop yields and to slow population growth in the poorest LDCs will worsen this already serious situation. By the year 2000, at least 64 of the world's 117 LDCsC29 in AfricaCwill be una­ble to feed their projected populations from their own water and land resources or from resource exports.



Food Quantity and Quality: Undernutrition, Malnutrition, and Overnutrition Poor people who cannot grow or buy enough food for good health and survival suffer from undernutrition. Survival and good health also require that people consume food contain­ing the proper amounts of protein, carbohydrates, fats, vitamins, and minerals. Most poor people are forced to live on a low-protein, high-starch diet of grains such as wheat, rice, or corn. As a result, they often suffer from malnutrition, or deficiencies of protein and other key nutrients.

Many of the world's desperately poor people suf­fer from both undernutrition and malnutrition. Such people barely survive on just two bowls of boiled rice (150 calories) and boiled green vegetables (10 calories) a day. Victims become weak, confused, listless, and unable to work. Disease kills most before they starve. Most of those who die are women and children.

Each year 20 million to 40 million peopleChalf of them children under age 5Cdie prematurely from undernutrition, malnutrition, or normally nonfatal infections and diseases, such as diarrhea, measles, and flu, worsened by these nutritional deficiencies. The World Health Organization estimates that diar­rhea alone kills at least 5 million children under age 5 a year.

Adults suffering from chronic undernutrition and malnutrition are vulnerable to diseases and too weak to work productively or think clearly. As a result, their children are also underfed and malnourished. If these children survive to adulthood, many are locked in a tragic malnutrition-poverty cycle that continues these con­ditions in each succeeding generation.

The two most widespread nutritional-deficiency diseases are marasmus and kwashiorkor. Marasmus (from the Greek "to waste away") occurs when a diet is low in both total energy (calories) and protein. Most victims of marasmus are infants in poor families in which children are not breast-fed or in which food quantity and quality are insufficient after the children are weaned. A child suffering from marasmus typi­cally has a bloated belly, thin body, shriveled skin, wide eyes, and an old-looking face. If the child is treated in time with a balanced diet, most of these effects can be reversed.


Kwashiorkor (meaning "displaced child" in a West African dialect) occurs in infants and children 1 to 3 years old who suffer from severe protein deficiency.

Typically, kwashiorkor afflicts a child whose mother has a younger child to nurse and whose diet changes from highly nutritious breast milk to grain or sweet potatoes, which provide enough calories but not enough protein. Children suffering from kwashiorkor have skin swollen with fluids, a bloated abdomen, lethargy, liver damage, hair loss, diarrhea, stunted growth, possible mental retardation, and irritability. If such malnutrition is not prolonged, most of the effects can be cured with a balanced diet.

Each of us must have a daily intake of small amounts of vitamins that cannot be made in the human body. Otherwise, we will suffer from various effects of vitamin deficiencies. Although balanced diets, vitaminfortified foods, and vitamin supplements have greatly reduced the number of vitamin deficiency diseases in MDCs, millions of cases occur each year in LDCs. For example, each year more than 500,000 children in LDCs are partially or totally blinded because their diet lacks vitamin A.

Other nutritional-deficiency diseases are caused by the lack of certain minerals, such as iron and iodine. Too little iron causes anemia. Anemia causes fatigue, makes infection more likely, increases a woman's chance of dying in childbirth, and increases an infant's chances of dying from infection during its first year of life. In tropical regions of Asia, Africa, and Latin America, iron-deficiency anemia affects about 10% of the men, more than one-half the children, two-thirds of the pregnant women, and about half of the other women.

Too little iodine in the diet can cause goiter, an abnormal enlargement of the thyroid gland in the neck, a condition that leads to deafness if untreated. It affects up to 80% of the population in the mountainous areas of Latin America, Asia, and Africa, where soils are deficient in iodine.

UNICEF officials estimate between half and two-thirds of the worldwide annual childhood deaths from undernutrition, malnutrition, and associated infections and diseases could be prevented at an average annual cost of only $5 to $10 per child. This lifesaving program would involve the following simple measures:


  1. immunization against childhood diseases such as measles

  2. encouraging breast-feeding

  3. preventing dehydration from diarrhea by giving infants a solution of a fistful of sugar and a pinch of salt in a glass of water

  4. preventing blindness by giving people a small vitamin A capsule twice a year at a cost of about 75 cents per person

  5. providing family planning services to help mothers space births at least two years apart

  6. increasing female education with emphasis on nutrition, sterilization of drinking water, and child care

While 15% of the people in LDCs suffer from undernutrition and malnutrition, about 15% of the people in MDCs suffer from overnutrition. This is an excessive intake of food that can cause obesity, or excess body fat, in people who do not suffer from glandular or other disorders that promote obesity. Overnourished people exist on diets high in calories, cholesterol-containing saturated fats, salt, sugar, and processed foods, and low in unprocessed fresh vegetables, fruits, and fiber. Partly because of these dietary choices, overweight people have significantly higher than normal risks of diabetes, high blood pressure, stroke, and heart disease.

Poverty: The Geography of Hunger If all the food currently produced in the world were divided equally among the earth's people, there would be enough to keep 6 billion people alive. However, if this food were used to give everyone the typical diet of a person in a developed country, it would support only 2.5 billion peopleChalf the present world population. The world's supply of food, however, is not now distributed equally among the world's people, nor will it be, because of differences in soil, climate, average income, and economic and political power throughout the world.

PovertyCnot lack of food productionCis the chief cause of hunger, malnutrition, and premature death throughout the world. The world's 1 billion desperately poor people do not have access to land where they can grow enough food of the right kind, and they do not have the money to buy enough food of the right kind no matter how much is available. About two-thirds of these people live in Asia and one-fifth in sub-Saharan Africa.

Increases in worldwide total food production and average food production per person often hide widespread differences in food supply and quality between and within countries. For example, about one-third of the world's hungry live in India, even though it is selfsufficient in food production. And although total and per person food supplies have increased in Latin America, much of this gain has been confined to Argentina and Brazil. In more fertile and urbanized southern Brazil, the average daily food supply per person is high. However, in Brazil's semiarid, less fertile northeastern interior many people are severely underfed. Overall, almost two out of three Brazilians suffer from malnutrition.

Food is also unevenly distributed within families. In poor families the largest part of the food supply goes to men working outside the home. Children (ages 1-5) and women (especially pregnant women and nursing mothers) are the most likely to be underfed and malnourished.

MDCs also have pockets of poverty and hunger. For example, a 1985 report by a task force of doctors estimated that at least 20 million peopleC1 out of every 11 AmericansCwere hungry, mostly because of cuts in food stamps and other forms of government aid since 1980. Half of these people were children.

Without a widespread increase in income and access to land, the number of chronically hungry and malnourished people in the world could increase to at least 1.5 billion by 2000Cone out of every four people in the world's projected population at that time.

Environmental Effects of Producing More Food

Both industrialized agriculture and subsistence agriculture have a number of harmful impacts on the air, soil, and water resources that sustain all life.

3.10.3 Methods of increasing world food production

Increasing Crop Yields Agriculture experts expect most future increases in crop production to come from increased yields per acre on existing cropland and from the expansion of green revolution technology to other parts of the world. Agricultural scientists are working to create new green revolutions by using genetic engi­neering and other forms of biotechnology. Over the next 20 to 40 years they hope to breed new high­ yield plant strains that have greater resistance to insects and disease, thrive on less fertilizer, make their own nitrogen fertilizer, do well in slightly salty soils, with­stand drought, and make more efficient use of solar energy during photosynthesis.


Seed companies, however, see little profit in devel­oping low-cost crops to be grown by the world's poor subsistence farmers. Therefore, such research must be funded by private organizations and by governments, especially those of MDCs.

If even a small fraction of this research and devel­opment is successful, the world could experience rapid and enormous increases in crop production in the early part of the next century. But some analysts point to several factors that have limited the spread and longterm success of the green revolutions:



  1. Without massive doses of fertilizer and water, green revolution crop varieties produce yields no higher and often lower than those from traditional strains.

  2. Areas without enough rainfall or irrigation water or with poor soils cannot benefit from the new varieties; that is why the second green revolution has not spread to many arid and semiarid areas.

  3. Increasingly greater and thus more expensive inputs of fertilizer, water, and pesticides eventually produce little or no increase in crop yields, as has happened to sorghum and corn crops in the United States. This diminishing-returns effect, however, typically takes 20 to 30 years to develop, so yields in LDCs using second green revolution varieties are projected to increase for some time. Scientists hope to overcome this limitation by developing improved varieties through crossbreeding and genetic engineering.


  4. × Without careful land use and environmental controls, degradation of water and soil can limit the long-term ecological and economic sustainability of green revolutions.

  5. The loss of genetic diversity caused when a diverse mixture of natural crop varieties is replaced with monoculture crops limits the ability of plant scientists to use crossbreeding or genetic engineering to develop new strains for future 'green revolutions. For example, a perennial variety of wild corn that replants itself each year, is resistant to a number of viruses, and grows well on wet soils was discovered several years ago. Unfortunately, the few thousand plants known to exist were growing on a Mexican hillside that was being plowed up. To help preserve genetic variety, some of the world's native plants and strains of food crops are being collected and stored in 13 Genetic storage banks and agricultural research centers around the world (Spotlight on this page).

Cultivating More Land Some agricultural experts have suggested that the world's cropland could be more than doubled by clearing tropical forests and irrigating arid lands, mostly in Africa, South America, and Australia. Others believe only a small portion of these potentially farmable (arable) lands can be cultivated because most are too dry or too remote or lack productive soils. Even if more cropland is developed, much of the increase would offset the projected loss of almost one-third of today's cultivated cropland and rangeland from erosion, overgrazing, waterlogging, salinization, mining, and urbanization.

SPOTLIGHT: Are gene banks the solution to preserving the world=s plant diversity?

Specimens of most of the world's native plants and food crops are kept in a series of gene tanks. Most plants are stored in the form of seeds. The seeds are usually stored dry and at cold temperatures. Warming them up and adding moisture makes them ready for use.


Despite their importance, plant gene banks are only a stopgap measure for preserving genetic diversity. One problem is that existing banks contain only a small portion of the world's known and potential varieties of agricultural crops and other plants.

Many plant species, such as potatoes, fruit trees, and many tropical plants, cannot be successfully stored. Many seeds rot and must periodically be replaced. Accidents such as power failures, fires, and unintentional disposal of seeds can cause irrecoverable losses. Furthermore, stored plant species do not continue to evolve. Thus, they are less fit for reintroduction to their native habitats, which may have undergone various environmental changes. Because of these limitations, ecologists and plant scientists warn that the best way to preserve the genetic diversity of the world's plant and animal species is to protect large areas of representative ecosystems throughout the world from agriculture and other forms of development. So far financial and political efforts by governments to accomplish this essential goal lag far behind the need. What do you think should be done?

Location, Soil, and Insects as Limiting Factors

About 83% of the world's potential new cropland is in the remote rain forests of the Amazon and Orinoco river basins in South America and in Africa's rain forests. Most of the land is located in just two countries, Brazil and Zaire.

Cultivation would require massive capital and energy investments to clear the land and to transport the harvested crops to distant populated areas. The resulting deforestation would greatly increase soil erosion. It would also reduce the world's precious genetic diversity by eliminating vast numbers of unique plant and animal species found only in these biomes.

Tropical rain forests have plentiful rainfall and long or continuous growing seasons. However, their soils often are not suitable for intensive cultivation. About 90% of the plant nutrient supply is in ground litter and vegetation above the ground rather than in the

soil. By comparison, as little as 3% of the nutrients in temperate-zone forests are stored above the ground.

Nearly 75% of the Amazon basin, roughly one­ third of the world's potential new cropland, has highly acidic and infertile soils. In addition, an estimated 5% to 15% of tropical soils (4% of those in the Amazon basin), if cleared, would bake under the tropical sun into brick-hard surfaces called laterites, useless for farming.

Some tropical soils can produce up to three crops of grain per year if massive quantities of fertilizer are applied at the right time, but costs are high. The warm temperatures, high moisture, and year-round grow­ing season also support large populations of pests and diseases that could devastate monoculture crops. Research has shown that crops grown in the tropics are attacked by up to ten times more species of insects and plant diseases than those grown in temperate zones. Weeds are especially troublesome, sometimes reducing monoculture crop yields to zero. Massive doses of pesticides could be used, but the same con­ditions that favor crop growth also favor rapid devel­opment of genetic resistance in pest species.

In Africa, potential cropland larger in area than the United States cannot be used for farming or livestock grazing because it is infested by 22 species of the tsetse fly, whose bite can give both people and livestock incurable sleeping sickness. A $120 mil­lion eradication program has been proposed, but many scientists doubt it can succeed.


Researchers hope to develop new methods of intensive cultivation in tropical areas. Some scientists, however, argue that it makes more ecological and eco­nomic sense not to use intensive cultivation in the tropics. Instead, farmers should use shifting cultiva­tion with fallow periods long enough to restore soil fertility. Scientists also recommend plantation culti­vation of rubber trees, oil palms, and banana trees, which are adapted to tropical climates and soils.




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