Read 2 articles and write 3 pages of essay along with chapter references and instructions attached below.

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Lecture Outlines

ENVIRONMENT the science behind the stories

Chapter 9

The Underpinnings of Agriculture

Lecture objectives  Outline the history of agriculture.  Explain the importance of soils to agriculture.  Discuss the fundamentals of soil science, including

soil formation and soil properties.  Describe how farmers supply water to crops, and

assess sustainable alternatives.  Explain the importance of pollinators to crop success.  Analyze causes, impacts, and solutions to soil

erosion and land degradation, and discuss solutions.  Summarize major policy approaches for

Farm to Table and Back Again – at Kennesaw State University  Campus dining services, such as at Kennesaw State

University, are becoming leaders with “closed-loop” culinary sustainability programs.  KSU runs three farms,

producing much of the produce consumed by the students.  Uneaten food waste is

composed and returned to the soil as fertilizer.

 The KSU dining commons was designed with sustainability in mind.  Floor-to-ceiling windows provide daytime lighting.  Food is prepared to order or in small batches,

minimizing waste.  Dishwashing systems have high water and energy

efficiency.  Water bottle refilling stations are available.  Recycling and compositing program diverts over

44,000 pounds of waste per month from the landfill.  Biodiesel is generated from used cooking oil.

 The farms are also designed to maximize sustainability.  Chemical pesticide and synthetic fertilizer use is

minimized.  Hydroponic stations supplied by rainwater produce

herbs, lettuce, and shiitake mushrooms.  Off-campus food sources are kept local whenever

possible.  This and other university operations help to serve as

models for nationwide agriculture reforms that could change how food is produced and delivered.

The Changing Face of Agriculture  Agriculture provides our most basic daily needs—

from the cotton in our clothes to the food on our plates.

 Agriculture is also responsible for some of our biggest impacts on the environment, making the development of sustainable practices essential.

Several factors underpin agriculture  Agriculture is the practice of raising crops and

livestock for human use and consumption.  Most of our food and fiber is obtained from cropland,

land used to raise crops for human use.  Rangeland, or pasture, is land used for grazing

livestock.  Growing crops and raising animals requires inputs of

resources—soil, sunlight, water, nutrients, and pollinators.

 Today, more than 1 out of every 3 acres of land on Earth is used to produce food and fiber.

Agriculture lead to modern societies  About 10,000 years ago, as the climate warmed,

many human cultures shifted from hunter-gatherers to permanent settlements with farming.

 Farming may have begun as the seeds of wild fruits, grains, and nuts unintentionally were planted and grew near human encampments.  These fruits may have been larger or tastier than the

wild versions, leading humans to begin breeding plants for desired traits.

 Evidence from archaeology suggests that agriculture was invented independently in many different cultures, each one specializing in a different local crop.

Industrial agriculture dominates today  In traditional agriculture, the work of cultivating,

harvesting, and distributing crops was performed by human and animal muscle power.  Traditional farmers would only produce enough food

for their own subsistence.  Industrial agriculture introduced large-scale

mechanization and fossil fuel consumption into agriculture.  Higher rates of irrigation, synthetic fertilizers, and

chemical pesticides reduced crop pests and weed competition, further increasing yields.

 Industrialized agriculture has also lead to the prevalence of monocultures, where farmers grow vast areas with single crops in orderly rows.  This contrasts with traditional polyculture, which

would have mixed crops in the same fields.  Beginning in 1950, the Green Revolution introduced

new technology, crop varieties, and farming practices to the developing world.  This helped to increase yields and reduce starvation,

but has also degraded soil, water supplies, and pollinators.

Sustainable agriculture reduces environmental impacts  Sustainable agriculture maintains healthy soil,

clean water, pollinators, and other vital resources.  The overall approach is to mimic the way natural

ecosystems function.  Achieving sustainable agriculture requires an

understanding of the soil, water, nutrients, and pollinators that underpin agriculture.

Review Questions 1. Which of these characteristics or practices is NOT

considered part of industrialized agriculture? a. Monocultures b. Subsistence farming c. Mechanized cultivating, planting, and harvesting d. Reliance on synthetic fertilizer and pesticides

Soil: A Foundation of Agriculture  Soil is a system consisting of

disintegrated rock, organic matter, water, gases, nutrients, and microorganisms.  Soil is derived from rock, but

shaped by microorganisms.  50% mineral matter, 5% organic

matter, and 45% pore space

Soil supports agriculture  Plants need soil to provide nutrients for growth,

structure for rooting, and a medium to hold water and nutrients for absorption through roots.

 Plants also depend on living organisms in the soil.  Many fungi, called mycorrhizae, for mutualistic

relationships with plants.  The fungi provides water and nutrients, while the

plant provides carbohydrates from photosynthesis.

Soil forms slowly  Soil formation begins during primary succession, as

water, air, and living organisms break down parent material in the lithosphere.

 Parent material is the base geologic material in a particular location. This may include:  Hardened lava or volcanic ash  Sediment deposited by glaciers or flowing water.  Wind-blown dunes  Bedrock, the mass of solid rock that makes up most

of the Earth’s crust

 Parent material is broken down into smaller particles by weathering.  Physical weathering results from wind, rain, freezing,

and thawing.  Chemical weathering occurs as water or gases

chemically alter rock.  Biological weathering involves living things such as

lichens producing acid or tree roots rubbing against rock.

 Further biological activity deposits organic matter in the form of decomposed organisms or waste.  Partially-decomposed organic matter is called

humus, and is very productive for plant life.

 Weathering and the accumulating of organic matter are influenced by  Climate: Warm, moist climates accelerate most

weathering processes.  Organisms: Plants and decomposers add organic

material.  Topography: Hills and valleys affect exposure to sun,

wind, water, and influence soil movement.  Parent material: Its composition influences soil

formation.  Time: Soil formation can take centuries, decades, or

millennia.  Soil is renewable, but at a very slow rate.

A soil profile consists of horizons  The movement and sorting of soil particles creates

distinct layers called soil horizons.  The entire cross-section of soil is the soil profile.

 Generally, the degree of weathering and concentration of organic matter decrease as one moves downward in a soil profile.

 Minerals dissolved or suspended in water can be transported downward in a process called leaching.

 The O horizon contains organic matter deposited by organisms.

 The A horizon is topsoil; a mixture of inorganic mineral components with humus mixed in from above.  Topsoil is the most

nutritive part of soil for plants and is vital for agriculture.

 The E horizon tends to be the most heavily leached, losing minerals like iron, aluminum, and silicate clay.

 The B horizon contains the minerals leached from above.

 The C horizon is partially-weathered parent material.

 The R horizon is bedrock.

Soils differ in quality  Soil characteristics vary widely from area to area.  A soil’s color indicates its fertility.  Black or dark brown soils are rich in organic matter.  A pale color indicates low organic matter.

 Soil texture is determined by the size of its particles.

 Clay particles are the smallest, less than 0.002 mm in diameter.

 Sand is the largest, between 0.05–2 mm in diameter.

 Silt particles fall in- between clay and sand.

 Soil with an even mixture of each particle is called loam.

 Clay soils have few pore spaces and are sticky, making it difficult for air and water to pass through.

 Sandy soils allow water to pass through too quickly, requiring frequent irrigation.

 Loam soils with medium- sized pores are considered the best for agriculture.

 Soil structure measures the “clumpiness” of soil.  Soil that is heavily clumped is considered compacted

and cannot absorb water as well.  Soils of intermediate pH values are best for plants.  Soil that is too acidic or alkaline may inhibit the

absorption of nutrients, leading to plant death.

Regional soil differences affect agriculture  The soils of the Amazon

rainforest are much less agriculturally productive than those in Iowa or Kansas.  The higher amount of

precipitation quickly leaches nutrients out of the topsoil and E horizon.

 Tropical farmers may practice swidden agriculture, where they cultivate a plot for a few years, then move on to another.  If enough time is allowed,

the soil and forest can recover.

 Plots are often burned first, a practice called slash-and- burn agriculture.

Review Questions 2. What soil horizon contains topsoil and is the most

productive for plants? a. The O horizon b. The A horizon c. The E horizon d. The B horizon

Review Questions 3. Which of these factors or changes would increase

the rate of weathering and accumulation of organic matter in soil? a. Less time b. Increased sheltering by hills c. Warmer climate d. Fewer plants and decomposers

Review Questions 4. What is the ideal soil texture for plant agriculture?

a. Soil with mostly clay particles b. Soil with mostly sand particles c. Soil with a mixture of silt, clay, and sand particles

(loam) d. Soil texture does not affect the success of plant

agriculture.

Water for Agriculture  The artificial provision of

water beyond what is received by precipitation is irrigation.  Irrigation is necessary with

water-intensive crops (like rice) and in areas with dry climates.

 Irrigation is the largest use of water, making up 70% of all fresh water withdrawn.

Salinization and waterlogging are easier to prevent than correct  Waterlogging occurs when irrigation oversaturates

the soil to the point where water drowns plant roots, depriving them of gases and suffocating them.

 Another problem of irrigation is salinization, the buildup of salts in surface soil layers.  In drier areas, the evaporation of water from the A

horizon may pull up mineral-rich water from lower horizons.  The only solution is to flush the land with less-saline

water, or plant salt-tolerant plants like barley.

Sustainable approaches to irrigation maximize efficiency  One effective way to reduce

water use is to better match crops and climate.  Government subsidies in some

arid areas has made water artificially inexpensive.

 Plants only use about 40% of the water applied by irrigation on average, switching to drip irrigation can also reduce water use.

Nutrients for Plants  Inorganic fertilizers are mined

or synthetically manufactured.  Organic fertilizers are made of

the remains or wastes from organisms, including manure, crop residue, charcoal, fresh vegetation, and compost.  Compost is a mixture produced

when decomposers break down organic matter in a controlled environment.

 Since the Green Revolution, farmers have increasingly relied on nutrients from inorganic fertilizers.  These nutrients are more quickly leached, creating