Soil & Agriculture

Increasing food production sustainably is necessary to feed the

rising population

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

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

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

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

Soil Profile (Horizon)• B horizon: subsoil• C horizon: larger rock particles, less weathered• R horizon: parent material; bedrock

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

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)

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

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)

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

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

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)

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)

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 ↑

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

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

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

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

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!)

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

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

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

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

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

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

Aquaculture

• Negative environmental impacts: ↑ incidence of disease among stocks, ↑ antibiotics, large waste production, escaped farm animals → disease, competition, new genetic material

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.

Energy Subsidy

Energy Expenditure in Food

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

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

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