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Plant Agriculture“The soil is the great connector of lives, the source and destination of all…

without proper care for it we can have no life.”

- Wendell Barry

● Plants need three basic components to grow:

● Energy, which they gain by absorbing sunlight through chlorophyll in their leaves.

● The elements carbon, oxygen and hydrogen for producing sugar, which they gain from the air and water.

● Smaller amounts of other elements like nitrogen, phosphorus, and potassium, which they absorb through the soil.

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The Great American Desert

● During the early exploration of the Great Plains in the United States, the land was found to be unsuitable for European-style agriculture because the ecosystems were too dry.

● The area was called the “Great American Desert”.

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● The area of the United States from the eastern Rockies through Nebraska is considered mixed or shortgrass prairie.

● Precipitation is lower than the tallgrass prairie to the east, leading to overall shorter plant species.

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● Farmers encouraged to settle into these arid shortgrass prairies also had a difficult time plowing, or turning over the soil.

● Cast iron plows would become stuck and caked with clay stuck inthe thick mat ofprairie grasses.

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● A blacksmith named John Deere invented a polished steel plow that was able to cut through the Midwestern soil.

● Further improvements, including gasoline tractors and combine harvesters, lead to the conversion of arid grassland into fields of corn, wheat, and cotton.

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● A combination of overhunting and habitat loss severely diminished the population of grey wolves and Eastern coyotes in the Great Plains.

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● Initially, farmers in the Great Plains were very successful, in part due to an unusually wet 10-15 year time period.

● Many homesteaders were convinced by a theory called “Rain Follows the Plow” which hypothesized that this wet period was actually the result of increased farming .

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● In the plains, the staple crop was hard red winter wheat, a producer that was planted in the fall, lay dormant over the winter, then harvested in early summer.

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● Staple crops are foods that are produced in large quantities to meet a steady demand.● The top staple crops worldwide are sugar, wheat, corn, and rice.

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Rank Commodity Production (Metric Tons)

1. Sugar cane 1.8 billion

2. Maize 885 million

3. Rice 722 million

4. Wheat 701 million

5. Milk (cow) 614 million

6. Potatoes 373 million

7. Sugar Beet 273 million

Source: http://faostat.fao.org/site/339/default.aspx

Staple Crops

● Most of the major world food staples are plants, because of the 10% rule of ecological energy pyramids.

● The 10% rule states thatonly about 10% of theenergy in one trophiclevel will be incorporatedinto the next.

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Millions of acres of shortgrass prairie in the Midwest were cultivated, with native plants like buffalo grass were replaced by domesticated ones.

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Soil ● Soil is a mixture of minerals and partially decomposed organic matter.

● Soil begins as rock, but is gradually broken down through erosion.

● Mechanical erosion is the physically breaking down of rock by wind and water.

● Chemical erosion changes the molecular structure of the soil compounds.

● Soil is divided into different layers based on composition, called horizons.

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● The O horizon is mostly non-decomposed plant litter.

● Found in forests

● The A horizon, also called topsoil, contains a lot of organic matter mixed with some minerals.

● Grasslands have the largest A horizon.

● The B horizon is mostly made of small particles of minerals that form clay.

● The last layer is parent material, which is the bedrock from which the soil was formed.

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● Following the stock market crash in 1929, wheat prices fell sharply.

● Farmers tried to recover their losses by overplanting and increasing crop yields.

● In 1931, a record crop of wheat was harvested. Prices continued to fall.

● In the winter of 1931-1932, a drought began that would persist for as long as 7 years in some areas.

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● The plains of Oklahoma, Texas, Colorado, and New Mexico experienced 14 dust storms so severe that visibility was cut to less than ¼ mile.

● The following year, 1933, had 38 severe dust storms.

VIDEO

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Erosion from Water● Mechanical erosion from rainfall takes four forms,

ranked by severity.

● Splash erosion occurs when soil is thrown by the force of a raindrop impact.

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● Sheet erosion is the removal of a thin layer of soil from a large area.

● Rill erosion occurs when water flowing down a slope carves small channels into the land.

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● Gully erosion is the most severe, caused by rapidly flowing water creating deep channels in the ground.

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Wind Erosion● Wind erosion is the

transportation and deposition of soil particles due to air currents.

● One of the worst storms of the Dust Bowl dumped 12 million pounds of eroded topsoil on Chicago.

Topsoil protected from wind erosion by native bluestem grass, New Mexico, 1957.

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Soil Conservation

● Multiple soil conservation techniques were part of the New Deal programs implemented by President Franklin Delano Roosevelt.

● Contour plowing reduces water erosion by planting crops along the slope of the land rather that straight up and down.

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● Many important commercial plants are row crops, meaning they must be grown in spaced rows.

● The spaces in between the plants are highly vulnerable to erosion.

● Cover crops are plants that completely cover the soil, protecting it from wind erosion.

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● Strip cropping alternates row crops like corn and cotton with cover crops like oats that completely cover the soil.

● Soil eroded from row crops will be trapped and held by the cover crops, keeping it within the farm.

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● Terracing converts steeply sloped land into a series of flattened terraces.

● The stair-like terracing slows the downward runoff of water, reducing erosion.

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● Rows of trees can serve as windbreaks, reducing erosion by wind.

● In response to the Dust Bowl, 220 million trees were planted, called the Great Plains Shelterbelt.

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● Biotic factors also contributed to the dust bowl. Swarms of grasshoppers descended on the few plants that survived.

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● There was also an overpopulation of jackrabbits, partially caused by the removal of their main predators – coyotes and wolves.

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● The Dust Bowl was the worst famine to ever hit the United States.● Famines are extreme scarcities of food, resulting in diets deficient in nutrients.

● Calories come from one of three macronutrients.● Carbohydrates, with a yield of 4kcal/gram, are our primary energy source.● Lipids, with a yield of 9kcal/gram, are what we store our energy as.● Proteins, with a yield of 4kcal/gram, make up many of our body structures.

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Human Nutritional Needs

● Undernutrition is the result of a diet that does not meet an individual’s basic energy (calories) requirement.

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● Humans also need smaller amounts of micronutrients, such as vitamins and minerals.

● A person with a diet lacking in specific micronutrients or macronutrients is considered to be malnourished.

● Kwashiorkor is caused by insufficient protein consumption, resulting in a fluid imbalance in the digestive system.

● The name is derived from the native language of Ghana, meaning “the sickness the older child gets when the next baby is born” due to a lack of breastmilk.

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● Anemia is the name of any condition that results in a decrease in the ability of blood to transport oxygen.

● Often caused by malnourishment – lack of iron in the diet.

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● A lack of iodine can result in a goiter; an enlargement of the thyroid gland.

Bangladeshi woman with a goiter. Source: John Paul Kay/Peter Arnold, Inc. 32

● As the human population grew in the 20th century, famines were becoming increasingly common, especially in developing countries.

● India especially, was on the brink of a massive famine in 1961.

● In 1968, a book entitled The Population Bomb predicted,“The battle to feed all of humanity is over. In the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date nothing can prevent a substantial increase in the world death rate..”

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Population Bomb

● The prediction of a worldwide famine never came true, because a series of advancements in farming lead to a massive increase in crop yields, starting in the 1960s.

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The Green Revolution

● The advent of industrialized farming, also called the Green Revolution, marked three major changes in modern agriculture.

1. The movement away from subsistence agriculture, where farmers produce to support their families, to industrialized monoculture, where only a few commercially valuable crops are grown.

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Field corn, which covers about 72 million acres across the United States.

2. The introduction of intensive artificial breeding of crops and genetic engineering.

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Photo from the Robert S. Peabody Museum of Archaeology, Phillips Academy, Andover, Massachusetts. All Rights Reserved.

3. The increased use of synthetic fertilizers and pesticides.

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● Irrigation, the application of water to soil, accounts for largest single share of global water use.

● Irrigation systems are compared with efficiency, a percentage of the amount of water withdrawn that actually makes it to the roots of target plants.● Most irrigation systems are inefficient, with only about 40% of the applied

water actually reaching the crops.

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Agricultural Water Usage

● Furrow irrigation works by delivering large amounts of water through small, parallel channels that run through the field.● 40-60% efficient.

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● Drip irrigation uses porous tubes above or below ground that gradually deliver water to the roots of individual plants. ● 90-95% efficient

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● Center-pivot irrigation involves a piece of equipment that rotates around a single point, creating a circle-shaped irrigation field.● 80% efficiency

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● Large-scale irrigation became available in the Great Plains following the discovery of the Ogallala Aquifer, a massive underground reservoir of water.

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● Lack of three nutrients can slow plant growth: nitrogen, phosphorous, and potassium.● These nutrients are depleted from soil

during each growing season and must be replenished.

● Inorganic fertilizer is synthetically made from mined minerals.● Use has grown nine-fold worldwide since

the 1950s.

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Fertilizer

● Organic fertilizers are derived from plant and animal matter.● Animal manure is the dung and urine of livestock.● Compost is organic matter that has been decomposed by bacteria, fungi, and

other microorganisms.

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● Some famers will minimize the fertilizer they need by using a technique called crop rotation.

● During one year, a nutrient-depleting crop (corn, tobacco) will be grown. ● The following year, legumes (beans, peas, lentils) that form mutualistic

relationships with nitrogen-fixing bacteria are planted.

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Nodules of nitrogen-fixing bacteria on a legume root.

● Agriculture accounts for about 15% of the total energy use in the United States.● This rate has increased as more and more farming has become mechanized.

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Energy

John Deere 2510H Nutrient Applicator

● Biological pests are any organisms that damage crops and reduce yields.● Examples: Insects, birds, rodents, weeds.

● Pesticides are chemicals that kill or control populations of these undesirable organisms.● Insecticides specifically target insect pests.● Herbicides specifically target weeds, or undesired plants.

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Pest Control

● Inorganic pesticides are derived from mined geologic minerals.● Chemically simple, meaning they are persistent

(non-degradable) in the environment.● Examples: Sulfur, arsenic, hydrogen cyanide, mercury,

lead.● Botanical pesticides are toxins produced by plants.

● Usually non-persistent and biodegradable.● Examples: Nicotine sulfate, rotenone.

● Synthetic pesticides are man-made and not found in nature.● Highly persistent.● Examples: DDT, organophosphates

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● One of the consequences of pesticide use is pesticide residue; chemicals that remain on food once they are applied.

● Persistent pesticides can bioaccumulate , forming higher and higher concentrations in organisms over a long period of exposure.

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● The bioaccumulation of DDT in predatory birds caused a thinning of eggshells and a decline in many bird populations.

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● Pesticide residues can also affect human health. This is most likely to occur in produce that we eat whole.

● The Dirty Dozen is a list, published by the Environmental Working Group, of produce that are more likely to absorb and retain pesticides.

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● Other types of produce, called the “Clean Fifteen”, have a protective layer that prevents them from absorbing as much pesticide residue or are naturally resistant to pests.

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● Pesticides have gradually become less effective as insects have evolved resistance to them.

● Pesticide resistance is the ability of an organism to develop a tolerance to a chemical.

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● Integrated Pest Management is a strategy where synthetic pesticides are used as a last resort in dealing with insects and weeds to minimize the issues of resistance and residue.

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Integrated Pest Management

● Suggested IPM tactics, in order of preference, include:

1. Cultural controls – Changing farming methods to minimize pest growth.

Example: Not overwatering to prevent mold and mildew growth.

2. Physical/mechanical controls – Barriers or traps.3. Biological controls – Introducing predators, parasites, or competitors to pests.

Example: Braconoid wasps lay their eggs in caterpillars.

4. Chemical controls – Botanical pesticides are preferred, followed by synthetic ones.

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● Organic foods, by definition, have been produced without any synthetic pesticides or fertilizer.● Organically-derived fertilizer is still used, as are botanical pesticides.

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Organic Agriculture

● Hydroponics is a method of growing plants without the use of soil.● Plants are grown with their roots immersed in water containing all the

necessary nutrients for growth.● Takes place in a

greenhouse, allowingfor a longer growing season and decreased need for pesticides.

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Hydroponics

● Another alternative to pesticides is to implant DNA into crops from other species that are resistant.● These are called Genetically Modified Organisms, or GMOs.

● Two of the most commonly grown crops in the United States, corn and soy, are now mostly genetically modified.

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Genetically Modified Organisms

● BT corn has been genetically modified to produce certain proteins from a species of bacteria called Bacillus thuringiensis. ● The proteins are poisonous to the European corn borer

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● Roundup-Ready corn is resistant to a glyphosate, an herbicide sold under the brand name Round-Up.● The herbicide is sprayed on a field, killing undesired weeds,

but leaving the corn.

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● As a result of the changes of the Green Revolution and the introduction of genetically modified organisms, crop yields have increased dramatically.

● In the United States, the biggest crop produced is corn, with 84 million harvested acres in 2011.

● As a result, corn is used as an ingredient in many types of processed foods, including animal feed.● About 70% of the carbon in the body of a typical American is from corn.

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Harvest