Soil & Agriculture
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Transcript of Soil & Agriculture
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Soil & Agriculture
Increasing food production sustainably is necessary to feed the
rising population
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Soil
• Agriculture: cultivating soil, producing crops, and raising livestock for human use/consumption
• Cropland: 38% of earth’s land sfc• Rangeland (pasture) used for livestock• Healthy soil is a mix of rock, organics, water,
gases, nutrients, and mictoorganisms
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Soil
• Agriculture began about 10,000 years ago• Traditional ag: needs human & animal muscle
power, tools, and simple machines• Industrial ag is newer; led to:• Monoculture: planting of a single crop• Green revolution applied tech to boost crop
yields in developing nations
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Soil as a System
• Parent material: base geological material (volcanic, glacial, sediments, or bedrock)
• Weathering of parent material is 1st step• Erosion is the process of moving soil
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Soil Profile
• Soil profile: cross-section from bedrock to surface
• O horizon: organic layer, leaf litter• A horizon: topsoil; humus, inorganics, organics
(unsustainable ag: depletes topsoil)• E horizon: zone of eluviation; leaching occurs
here and in topsoil
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Soil Profile (Horizon)• B horizon: subsoil• C horizon: larger rock particles, less weathered• R horizon: parent material; bedrock
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Soil Characteristics
• Characterized by color, texture, pH, cation exchange
• 12 major groups (soil triangle)• Color can indicate fertility• Texture: clay, silt, sand; loam is an even mix• pH: acid or alkaline; influences plant growth• Cations (K+, Mg2+, Ca2+) measure soil fertility
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Soil Degradation: Problems
• Erosion: wind and water (splash, sheet, rill and gully)
• Desertification is a loss of 10% productivity due to erosion, compaction, forest removal, overgrazing, salinization, etc
• Dust Bowl was monumental (drought was major factor)
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Soil Degradation: Solutions
• Soil Conservation Service pioneered measures to slow degradation
• Crop rotation: alternating type of crop from year to year
• Contour farming: plowing furrows along natural contours
• Intercropping : alternate bands of different crops across a slope
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Soil Degradation: Solutions
• Terracing: cutting level platforms into steep hillsides
• Shelterbelts: rows of trees planted along fields to act as a windbreaker
• Protecting and restoring plant cover is most effective
• Irrigation: boosted productivity but lead to probs such as waterlogging (soil, root damage)
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Soil Degradation: Solutions
• Salinization is easier to prevent than reverse• Fertilizers boost crops but are overused• Inorganic fertilizers are mined or
manufactured• Organic fertilizers consist of natural materials• Other impacts: grazing, forestry
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Race to Feed the World
• Food security: guarantee of adequate, reliable, and available food supply to all people at all times
• Dramatic increases in production due to devotion of more energy to ag.; irrigation, fertilizer, pesticides, increase in cultivated land, and more productive crop and livestock varieties
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Race to Feed the World
• Undernourished: receive < 90% of daily caloric needs• Overnutrition: too many calories each day• Malnutrition: shortage of the nutrients the body
needs• ½ of the world’s pop. Lives on < $2 per day• Kwashiorkor results from high starch, low protein diet
(presents abdominal swelling & edema)• Marasmus is caused by lack of proteins and calories
(emaciation)
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Race to Feed the World
• Vitamin deficiencies are also harmful globally• WHO: estimates > 250,000 children worldwide
become blind due to vitamin A deficiency• Anemia (iron deficiency) affects 3 billion people
(WHO)
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Race to Feed the World: Green Revolution
• Transfer new tech to developing nations • Began in 1940 – new wheat variety• Benefits and probs (of course):• Greater productivity• Cultivated area of world ↑ 33%, energy inputs
↑ 80x between 1900 – 2000• Decrease in biodiversity• Desertification, salinization, pollution ↑
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Pests and Pollinators
• Pest: any organism that damages crops• Weed; competes with crops• Pesticide use – 1000’s of them• 900 million pounds of active pesticides used in
US annually• Biological control: pits one organism against
another; control may become pest• Bacillus thuringiensis (Bt) is a naturally
occurring soil bacterium
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Pests and Pollinators
• Resistance- pest populations may evolve resistance to a pesticide over time. These are said to be resistant.
• Pesticide treadmill- the cycle of pesticide development followed by pest resistance, followed by development of a new pesticide
• Persistent- pesticides that remain in the environment a long time
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Pests and Pollinators
• Integrated Pest Management (IPM): uses numerous techniques (biocontrol, pesticides, habitat alteration, crop rotation, transgenics, alternative tillage, mechanical pest removal)
• Pollination is important; carried out by insects and to a lesser degree, wind
• Planting flowering plants that nourish and provide nesting sites for native species can help maintain biodiversity
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Genetic Modification of Food
• Genetic engineering: any process by which an organism’s genetic material is manipulated by adding deleting or changing DNA segments
• Genetically modified organisms (GMOs) : genetically engineered by using recombinant DNA technology
• Genetic modification is not new
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Genetic Modification of Food
• Possible impacts: dangerous to eat (allergens), escape and pollution of ecosystems, increase resistance of pests, transfer to other crops
• Precautionary principle: do not undertake action until ramifications are clear
• Ethical issues• Monopoly of food supply• Most crops – pesticide tolerance to same
company’s pesticide (Monsanto!)
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Genetic Modification of Food
• Public relations has played a role in perception (Percy Schmeister v Monsanto)
• Europeans’ uneasiness• Some countries approve of GMOs, some refuse
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Preserving Crop Diversity
• Crop diversity provides insurance against failure• Monocultures place food systems at risk• Wild & domestic crop relatives contain
reinvigorating genes (resistance to drought, etc)• Many fruit and veggie crops ↓ diversity by 90%
in last century• Market forces have discouraged diversity
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Preserving Crop Diversity
• Seed banks (gene banks): institutions store seeds from crop varieties in cold, dry conditions to ↑ long-term viability
• Large banks include the US national Seed Storage Laboratory, the Royal Botanic garden’s Millennium Seed Bank, Seed Savers Exchange (Iowa), Wheat and Maize Improvement Center (CIMMYT) in Mexico
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Feedlot Agriculture (CAFO)
• World population of domesticated animals tripled between 1961 and 2000
• Per capita consumption doubled between 1950 and 2000
• Feedlots (factory farms): operations in which animals are housed in large warehouses or pens and fed energy-rich foods
• Decrease in overgrazing and soil degradation
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Feedlot Agriculture (CAFO)
• Waste is a problem – odor, surface and groundwater pollution
• Lower food chain sources → greater use of sun’s energy → more people can be fed
• Producing chickens and eggs requires least amount of space, beef requires the most
• What we choose to eat indirectly chooses how we make use of resources
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Aquaculture
• Raising fish and shellfish on “fish farms” in controlled environments
• May be the only way to meet the demand; most fisheries are overharvested
• Benefits: reliable source of protein, sustainable on a small scale, large scale = ↑ nation’s food security, reduces pressure on wild stocks, less use of fossil fuels, safer work environment
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Aquaculture
• Negative environmental impacts: ↑ incidence of disease among stocks, ↑ antibiotics, large waste production, escaped farm animals → disease, competition, new genetic material
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Energy Subsidy
Energy input per calorie of food produced• Example: If we use 5 Calories of energy to
produce food, and we receive 1 Calorie when we eat that food, the food has an energy subsidy of 5
• It takes 20 kg of grain to produce 1 kg of beef. It takes 2.8 kg to produce 1 kg of chicken meat. Compare the energy subsidies.
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Energy Subsidy
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Sustainable Agriculture
• Farming that does not deplete soils faster than they form, does not reduce the amount of healthy soil, clean water, and genetic diversity
• Low-input agriculture: uses smaller amounts of pesticides, fertilizers, growth hormones, water, fossil fuel energy
• Organic agriculture uses no synthetic fertilizers or pesticides
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Sustainable Agriculture
• No-till agriculture• 1990: Organic Food Production Act established
standards for organic foods• Accounts for 1% of food expenditures• Production and demand is increasing• Health benefits• Government initiatives
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Sustainable Agriculture
• Farmers’ markets• Community Supported Agriculture (CSA)• The average food product sold in the US travels
at least 1400 miles and is often chemically treated to preserve freshness and color