Chapter 10 Farming: Conventional and Sustainable Practices

agriculture has dramatically changed what

our environment, altering patterns of vegetation soils and water resources worldwide.

some agricultural lands have been depleted in

in just a few decades while others have been sustained for centuries

describe soil

Soil is a renewable resource that develops gradually through the weathering of rocks and the accumulation of organic material.

describe the accumulation of topsoil

The accumulation of topsoil is a very slow process. Under the best circumstances, it accumulates at a rate of about 1 mm/year

With careful management, soil can be replenished and renewed indefinitely

most farming techniques do what to soil

deplete soil through erosion and removal of organic material. Severe erosion rates can exceed 25 mm soil/year.

what are the 6 components of soil

sand and gravel

silts and clays

dead organic material

soil fauna and flora

water

air

why is soil a marvelous, complex substance

an entire ecosystem that is hidden to most of us

Variation in the 6 components of soil can produce an almost infinite variety of soil types

what is the most important characteristic of soil

soil texture: the amount of sand, silt, and clay

what soils are considered best for agriculture

Loam soils are considered best for agriculture because they are a mixture of sand, silt, and clay

describe the brazilian tropical soils

Brazilian tropical soils are deeply weathered red clays which have little organic material. They hold few nutrients and water

describe the soils of central US

The rich, black soils of the central US are rich in nutrients and organic material and contain a mixture of sand, silt, and clay to hold moisture well

how are nutrients recycled in soil

Soil bacteria, algae, and fungi decompose leaf litter making recycled nutrients available to plants

a single gram of soil can contain

can contain hundred of soil bacteria and 20 meters of tiny fungal strands

what can tiny worms and nematodes do for soil

Tiny worms including nematodes process organic material and create air spaces as they burrow

Larger insects, spiders, and mites loosen and aerate the soil as well

mycorrhizal symbiosis

an association between plant roots and certain fungi. The plant feeds the fungus and the fungus provides water and inorganic nutrients to the plant enhancing growth

soil horizons

Soils are stratified into horizontal layers called soil horizons

Horizons taken together make up the soil profile

which soil horizon is made up of leaf litter, contains the most soil organisms, and partially decomposed organisms

O Horizon = organic layer

A Horizon

surface soil, mineral particles mixed with organic material

Which soil horizon is most important to food production

A Horizon

E Horizon

washed out, depleted of soluble nutrients

B Horizon

subsoil, often dense texture due to clays

C Horizon

weathered rock fragments with little organic material

R Horizon

parent material is the mineral material on which the soil is built, can be bedrock

how do we identify soils

Because soils are so important to our survival, we identify soils largely in terms of the thickness and composition of their upper layers

what is the dominant soil in the farm belt

In the farm belt, the dominant soils are mollisols. These soils have a thick, organic-rich A Horizon which developed from deep dense roots when this land was covered by prairie grasslands

alfisols

Alfisols are another soil type important for farming. These soils developed in deciduous forests and have a thinner A Horizon and less organic material

what soils dominant most of the soils of farming in the US

mollisols and alfisols

what percentage of the earth's land is currently in agricultural production

Approximately 12.5% of the earth's land area is currently in agricultural production. Up to 4 times as much could potentially be converted to agricultural use. However, much of this additional land suffers from constraints such as steep slope, soggy soil, too cold, too dry, or has too much salt

what is the ecological effects of converting land to agriculture

The ecological effects of converting these lands to agriculture include loss of biodiversity, clean water and other ecological services provided by these grasslands or forests.

arable land distribution

Arable land is unevenly distributed across the world. The best farming occurs in moderate climates with thick, fertile soil.

what countries are well suited for agriculture

North America and Europe are particularly well suited to growing while some other parts of the world lack suitable soil, topography, and climate

gains in agriculture are due to what

Gains in agricultural production have come from increased fertilization, pesticides, and irrigation rather than more land

as productivity in North America and Europe increases what is a result

As productivity in North America and Europe has increased in recent years some marginal lands have been retired and less land is now cultivated than in the past.

how many hectares of cropland is made unstable each year

Every year, about 3 million hectares of cropland worldwide are made unusable by erosion and another 4 million hectares are converted to non-agricultural uses

Most land degradation happens slowly as soil washes or blows away, salts accumulate and organic matter is lost

As a consequence of these processes, as well as increases in world population, arable lands worldwide have shrunk from 0.38 ha/person in 1970 to 0.23 ha/person in 2000

Sheet erosion

a thin layer of surface removed

rill erosion

small rivulets of running water gather together and cut small channels

gully erosion

rills enlarge to form bigger channels too large to be removed by normal tillage

stream bank erosion

washing away of soil from banks of streams and rivers

what can equal or exceed water erosion

Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land

desertification

conversion of productive land to desert

what intensive farming practices are responsible for erosion

Row crops leave soil exposed

Weed-free fields

Removal of windbreaks

No crop rotation or resting periods of fields

Continued monoculture cropping can increase soil loss tenfold

desertification threatens how much land

Desertification of productive lands threatens ⅓ of the earth's surface and over 1 billion people

what lands are highly susceptible to desertification

Rangelands and pastures are highly susceptible to desertification due to overgrazing and soil degradation

Which 2 areas are of particular concern for desertification due to rapid population growth, poverty, and removal of trees for fodder and firewood?

africa and china

all plants need what to grow

water

what accounts for the largest single share of global water use

Agriculture accounts for the largest single share of global water use. This majority of irrigation water is lost to seepage and evaporation. Drip irrigation is more effective

what encourages over use of water in some countries

low cost

over watering can result in

Waterlogging: soil completely saturated with water

Salinization: mineral salts accumulate in soils; lethal to plants

lack of what nutrients often limits plant growth

Lack of nitrogen, potassium, and phosphorus

adding what usually stimulates growth and crop yields

Adding nutrients via fertilizer usually stimulates growth and increases crop yields

overusing what can cause water pollution

fertilizer

what are alternative methods to replenish soil nutrients

manure and nitrogen-fixing bacteria

what could increase crop production in africa

fertilizer use

when did the use of fossil fuels begin

Fossil fuel use began with the advent of tractors in the 1920s and increased after WWII with the use of natural gas to produce synthetic fertilizers

In the decades that followed, increased reliance on mechanization has increased the reliance on fossil fuels

Today, the US food system consumes 16% of total energy use

most foods require what

Most foods require more energy to produce, process, and transport than we get from eating them. Eating locally grown foods can have a less environmental impact.

biological pests

organisms such as insects of fungi that compete with humans to consume agricultural crops

types of pesticides

Pesticides are chemicals that kill biological pests

Biocides kill a wide variety of living organisms

Herbicides kill plants

Insecticides kill insects

Fungicides kill fungi

what isthe most common method of controlling pests in modern agricultural production

synthetically produced pesticides

have pesticides been used in the past

The ancient Sumerians used sulfur to kill insects and mites over 5000 years ago

The ancient Chinese used mercury and arsenic to control pests

Greek and Romans used oil, sulfur, ash, lime, and other natural materials to protect their livestock and crops from pests

Crop rotation, burning of fields and use of biological controls have also been used by a variety of ancient cultures

when did the era of synthetic organic pesticides begin

The era of synthetic organic pesticides began in 1939 with DDT

DDT's

DDT was inexpensive, stable, easily applied, and highly effective

By the 1960s, evidence showed DDT was concentrating through food chains

Which species were harmed the most from the application of DDT?

Carnivorous birds such as eagles suffered eggshell thinning leading to an inability to reproduce

Who warned the public about the dangers of pesticide overuse, specifically DDT?

Rachel Carson in 1962

when was DDT banned in the US

late 1960s

are DDT's still in use

DDT is still used in developing nations, especially Africa to control mosquitos to prevent malaria

since DDT what has happened

Since the development of DDT, many new synthetic pesticides have been developed

Like DDT, many of them have proven to have unintended consequences on non-target species

the EPA estimates total pesticide use to be

total pesticide use in the US amounts to about 5.3 billion pounds annually

what percentage of pesticides are used in agriculture or food storage and shipping

Roughly 80% of all conventional pesticides applied in the US are used in agriculture or food storage and shipping

Home and garden use accounts for about 14% of US pesticide use annually

organophosphates

most abundantly used synthetic pesticides

Round-up is the most commonly used organophosphate herbicide

Other organophosphates are used as insecticides and inhibit cholinesterase, an enzyme necessary for nervous system function

Quickly degrades and does not persist

chlorinated hydrocarbons

fast-acting and highly toxic to sensitive organisms

Ex: atrazine, mothballs, and DDT

Persistent and concentrate in food chains

fumingants

small molecules which are delivered as gas to penetrate soil or other materials

Used in fungus control on strawberries or to prevent insect/rodent damage to stored grains

Extremely dangerous to workers and restricted or banned in some areas

inorganic pesticides

compounds of toxic elements such as mercury or arsenic. Highly toxic, indestructible and persistent. Generally, act as nerve toxins

natural organic pesticides

generally extracted from plants and include such pesticides as nicotine or pyrethrums. Toxic to insects and may prevent wood decay

microbial agents and biological controls

living organisms or toxins derived from them that are used in place of pesticides

how are ladybugs used as a biological control

Ladybugs are often used to control aphid populations. This is a form of biological control.

widespread use of pesticides brings what

brings a number of environmental and health risks

non-target species

broadly sprayed pesticides might not reach the intended target and instead kill beneficial organisms

pest resurgence

a few resistant pests survive the pesticide and survive to repopulate the area with more resistant pests. Resistant pests require finding new pesticides

what are the biggest threats to bee health

Pathogens

Parasites

Climate

Management

Nutrition

Pesticides

persistent organic pollutants

are chlorinated hydrocarbons like DDT that are stable, soluble in fats and toxic. They can travel far from the point of dispersal. Stored in fat and tend to bioaccumulate.

High levels have been detected in predators at the upper levels of food chains such as polar bears and eagles

what is the grasshopper effect

When POPs accumulate in polar regions because they evaporate from warm regions and condense in cold regions

when were POPs banned globally

Many POPs were banned globally in 2001 when 127 countries signed a treaty. The use of these chemicals was previously banned or restricted in developed countries, but US companies continued to sell POPs in underdeveloped countries where regulations were lax. Many pesticides then return to the US in agricultural products

Since the treaty banning of POPs, other pesticides have taken their place

what percent of conventionally grown foods contain pesticide residue

A USDA study shows 73% of conventionally grown foods in the US contain residue of at least one pesticide

chronic or long-term health effects of pesticides

Chronic or long-term health effects are difficult to conclusively document, but effects may include cancer, birth defects, neurological problems, and immune system problems

Numerous studies have shown organic, sustainable agriculture is more eco-friendly and leaves soil healthier than intensive, chemical-based monoculture cropping

organic food

Organic food must be produced without the use of hormones, antibiotics, pesticides, synthetic fertilizers, or GMs

Animals must be raised on organic feed, given access to the outdoors, given no steroids, or growth hormones, and given antibiotics only to treat disease

why are critics disappointed with the limited scope of the definition of organic

They hope to include growing food in harmony with nature, food distribution based on co-ops, farmers markets, and local production, food should be simple, wholesome, nutrition

are processed ingredients allowed in organic foods

yes, presently

what are some doubts of organic foods

Some doubt whether organic growers can produce enough to feed everyone

what are some behavioral changes that reduce pest

Crop rotation

Mechanical cultivation

Flooding fields

Habitat diversification

Adjusting planting times

Plant mixed cultures

Tillage at the right time

Introduce predators or pathogens such as insects to eat weeds, plants that use their own pesticides, bioengineering, and hormones the disrupt development or attract insects to traps

what is integrated pest management

It is a flexible, ecologically based strategy that is applied at specific times against specific pests. Some use of pesticides takes place, but the time, type and method of application are controlled, can use trap crops. IPM is being used successfully all over the world. It cuts pesticide use while maintaining yields

trap crops

small areas are planted before the main crop. These plants mature first and attract the insects, and the trap crop is then destroyed along with the pest

true or false: Integrated Pest Management aims to increase pesticide usage.

false

managing topography

Contour plowing: plowing across the slope to slow the flow of water

Strip farming: planting different crops in alternating strips along land contours

Terracing: shaping the land to create level shelves of the earth to hold water and soil

Planting perennial species

methods of providing ground cover

Annual row crops cause the highest rate of erosion because they leave the soil bare for much of the year

Plant cover crops such as clover after harvest

Interplant 2 different crops in the same field, harvest one; the other is left to hold the soil. Double harvest is an advantage as well

Mulch

low input sustainable agriculture

Small scale, low input agriculture

No synthetic chemicals

Raising cows on pasture grass rather than grain

Antibiotics used only to treat diseases

Typically produces smaller yields, but production costs are lower and prices are higher so net gain is higher

Preserves rural culture

what can a vegetarian diet do

A vegetarian diet ca reduce environmental impact related to energy input

An organic diet can reduce environmental impact related to pesticide use

what is a locavore

A person who eats locally grown, seasonal food. Has an even greater impact

neonicotinoid

pesticides that are now the most widely used group of insecticides globally. They are used to control insects and minute concentrations can transfer to pollen and fruits

pesticide treadmill

as resistant pests evolve, there is an ever-increasing need for newer, better pesticides

how are ladybugs used as a biological control

Ladybugs are often used to control aphid populations. This is a form of biological control.