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 1 ● 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. 2 The Great ● During the early exploration of the Great Plains in the United States, the land was American found to be unsuitable for European-style Desert agriculture because the ecosystems were too dry. ● The area was called the “Great American Desert”. 3 ● 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. 4 ● 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 in the thick mat of prairie grasses. 5 ● 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. 6 ● A combination of overhunting and habitat loss severely diminished the population of grey wolves and Eastern coyotes in the Great Plains. 7 ● 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 . 8 ● 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. 9 Staple Crops ● 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. 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 10 ● Most of the major world food staples are plants, because of the 10% rule of ecological energy pyramids. ● The 10% rule states that only about 10% of the energy in one trophic level will be incorporated into the next. 11 Millions of acres of shortgrass prairie in the Midwest were cultivated, with native plants like buffalo grass were replaced by domesticated ones. 12 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. 13 ● 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. 14 ● 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. 15 VIDEO ● 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. 16 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. 17 ● 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. 18 ● Gully erosion is the most severe, caused by rapidly flowing water creating deep channels in the ground. 19 Wind Erosion ● Wind erosion is the Topsoil protected from transportation and wind erosion by native deposition of soil bluestem grass, New particles due to air Mexico, 1957. currents. ● One of the worst storms of the Dust Bowl dumped 12 million pounds of eroded topsoil on Chicago. 20 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. 21 ● 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. 22 ● 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. 23 ● Terracing converts steeply sloped land into a series of flattened terraces. ● The stair-like terracing slows the downward runoff of water, reducing erosion. 24 ● 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. 25 ● Biotic factors also contributed to the dust bowl. Swarms of grasshoppers descended on the few plants that survived. 26 ● There was also an overpopulation of jackrabbits, partially caused by the removal of their main predators – coyotes and wolves. 27 Human Nutritional Needs ● 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. 28 ● Undernutrition is the result of a diet that does not meet an individual’s basic energy (calories) requirement. 29 ● 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. 30 ● 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. 31 ● 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 Population Bomb ● 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..” 33 The Green Revolution ● 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. 34 ● 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 Field corn, which covers about 72 million acres across the crops are grown. United States. 35 2. The introduction of intensive artificial breeding of crops and genetic engineering. Photo from the Robert S. Peabody Museum of Archaeology, Phillips Academy, Andover, Massachusetts. All Rights Reserved. 36 3. The increased use of synthetic fertilizers and pesticides. 37 Agricultural Water Usage ● 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. 38 ● Furrow irrigation works by delivering large amounts of water through small, parallel channels that run through the field. ● 40-60% efficient. 39 ● Drip irrigation uses porous tubes above or below ground that gradually deliver water to the roots of individual plants. ● 90-95% efficient 40 ● Center-pivot irrigation involves a piece of equipment that rotates around a single point, creating a circle-shaped irrigation field. ● 80% efficiency 41 ● Large-scale irrigation became available in the Great Plains following the discovery of the Ogallala Aquifer, a massive underground reservoir of water.