Unit 5: Soil Systems & Society Flashcards
What are four reasons why soil is important?
- All of the food we consume depends on soil
- Soil is a habitat for many organisms
- Soil stores both water and nutrients for ecosystems
- Soil filters the water that passes through it and alters its chemistry
How long can the formation of 1 cm of soil take to renew?
15-100 years (depending on climate)
pedosphere
soil sphere; a thin bridge between the biosphere and lithosphere
How is soil produced?
soil is produced by the weathering of rock, deposition of sediments, and decomposition of organic matter
How long does it take for soil to be produced?
200-1000 years
What are the four main components of soil?
- mineral particles from underlying rock
- organic remains that have come from plants and animals
- water within the spaces between the grain
- air within the spaces between the grain
What is the soil ratio of solids to pore spaces?
Soil is typically a 50:50 mixture of solids and pore space
What is the function of air in soil?
provides oxygen for organisms and plant roots
What are the 4 functions of water in soil?
- allows dissolved mineral salts to be available to plants
- rapid downward movement of water causes leaching
- rapid upward movement causes salinization
- large volumes of water in the soil can cause water logging leading to anoxic conditions and acidification
leaching
minerals dissolved in water move through soil
What is a function of rock particles in soil?
provides the skeleton of the soil
What are the 3 functions of humus in soil?
- gives the soil a dark color
- as it breaks down, it returns mineral nutrients back to the soil
- absorbs and holds on to a large amount of water
What are the 2 functions of soil organisms in soil?
- decompose dead organic matter
- larger soil animals help to mix and aerate soil
What kinds of organisms reside in soil?
soil invertebrates, microorganisms, and large animals
What are two kinds of rock particles?
insoluble and soluble
What are examples of insoluble rock particles?
gravel, sand, silt, clay, and chalk
What are examples of soluble rock particles?
mineral salts, compounds of nitrogen, phosphorus, potassium, sulphur, magnesium, etc.
humus
partially decomposed bodies of dead plants and animals
What elements make up the air in soil?
mainly nitrogen and oxygen
From where does water enter soil?
water either seeps down from precipitation or moving up from underground sources by capillary action
soil horizons
separate zones (horizontal layers) within soil
soil profile
cross-section view of soil
O Horizon
surface litter
A Horizon
top soil
In the O Horizon, what happens to newly added organics such as freshly fallen leaves, twigs, etc.?
Fungi, bacteria, and many different kinds of animals will start to decompose the dead material
What makes up the top soil in the A Horizon?
a mixture of humus and inorganic materials such as clay, silt, or sand
About how many organisms (bacteria) does healthy soil contain?
billions of nematodes, bacteria, fungi, etc. per handful
E Horizon
transitional zone
B Horizon
the layer where most of the decomposed matter and soluble minerals eventually deposit
C Horizon
weathered rock from which the soil forms
R Horizon
plant material (bedrock)
How many different sized particles is the mineral portion of soil made up of?
3 different sized particles
What determines a soil’s texture?
A soil’s texture depends on the relative proportions of sand, silt, and clay particles.
What is the particle diameter of clay?
< 0.002 mm
What is the particle diameter of silt?
0.002 - 0.05 mm
What is the particle diameter of sand?
0.05 - 2 mm
How does one perform the “finger test”?
moisten soil and rub it between your fingers
How do sandy soils feel?
Sandy soils are gritty and fall apart easily.
How do silty soils feel?
Silty soils feel a little slippery, like baby powder, and hold together better than sandy soils.
How do clay soils feel?
Clay soils feel sticky and can be rolled into a ball easily.
loam
soil that has fairly equal proportions of sand, silt, and clay
What is loam ideal for?
agriculture
What do the sand particles in loam allow for in terms of agriculture?
sand particles provide good drainage and air supply
What do the clay particles in loam allow for in terms of agriculture?
clay particles retain water and supply nutrients
What do the silt particles allow for in terms of agriculture?
silt particles help to hold the sand and clay together
porosity
the amount of space between particles
permeability
the ease at which gases and liquids pass through
Why do sandy soils have high permeability?
sandy soils have fewer micropores and less total space, but the pores are too large for adhesion, therefore liquids can easily pass through, so sandy soils have high permeability.
Why do clay soils have high porosity?
clay soils have a lot of micropores, which results in more space
Why do clay soils have high mineral content yet low fertility?
water adheres to micro pores in clay, which locks dissolved minerals so plants can’t access it
Why do clay soils have low permeability?
the water adheres to the clay surface
Why do clay soils tend to be more acidic?
as more water is absorbed, clay particles fill with positive hydrogen ions; this binds soil water tightly to the clay particles a makes the soil more acidic
What is an effect of the acidification of soil?
reduces ability to store other positive ions
What is an effect of the reduction in pH?
toxic ions are made available to plants like iron and aluminum
What are the effects of acid rain in Northern Europe?
acid rain has turned the soil acidic, making more aluminum and iron available, causing damage to forestry industry through needle death
What type of resource is fertile soil?
non-renewable
Why is fertile soil a non-renewable resource?
soil formation takes a long time and soil use often exceeds soil formation
What are the main nutrients in fertile soil?
nitrates, phosphates, and potassium
What are 2 ways nutrients can leave soil?
nutrients can be leached out of soil or removed when crops are harvested
How do nutrients naturally return to soil?
decomposition
subsistence
provisions of food by farmers for their own families or the local community - there is no surplus
Why are subsistence farmers vulnerable to food shortages?
little food is stores as there is no surplus because subsistence farmers are unlikely to produce more food than they need
What are three characteristics of subsistence farming?
- mixed crops
- a lot of human labor
- low input of energy in terms of fossil fuels or chemicals
commercial (industrialized)
this kind of farming takes place on a large, profit-making scale, maximizing yields per hectare
In commercial farming, what do high levels of energy and technology input result in?
usually large outputs
What are 2 characteristics of commercial farming?
- often a monoculture of one crop or animal
- goal is to maximize yield
extensive
uses more land but lower density of animals/crops
intensive
use land more intensively with high levels of input and output per unit area.
What is an example of intensive farming?
feedlots
pastoral
raising animals
Where does pastoral farming usually take place?
on land not suitable for crops
arable
growing crops on good soils to eat directly or to feed to animals
mixed
farming has both crops and animals; animal waste is used to fertilize the crops and improve soil structure and some crops are fed to the animals
malnutrition
umbrella term for “bad” nutrition
In regards to malnutrition, nutrients can be (3 things)…
- lacking (undernourishment, usually a lack of calories)
- excessive (over nourishment, usually too many calories leading to obesity)
- unbalanced (the wrong proportion of micro-nutrients)
According to the FAO, how many people in the world are lacking nutrients?
925 million people
What percent of people who are lacking nutrients in MEDCs?
2%
What percent of people who are lacking nutrients in LEDCs?
98%
What percent of the world doesn’t have enough food?
13%
How is access to food in MEDCs?
the cost of food is relatively cheap, and food is purchased out of choice or preference
How is access to food in LEDCs?
many populations struggle to produce enough food to sustain their populations
cash crops
crops that are grown for export/profit instead of feeding indigenous population
What are example of cash crops?
coffee, flax, biofuels, some cereal grains
What are 4 factors that influence what we choose to grow and eat?
- climate
- culture/religion
- political
- socio-economic
How do we artificially alter climate to grow certain crops?
greenhouses and irrigation
How does culture/religion affect what an individual grows/chooses to eat?
some religions proscribe certain foods and tradition often determines preference
How do politics affect what we grow/choose to eat?
governments can subsidize certain foods while putting tariffs on others, encouraging/discouraging production
How does socio-economic status determine what we grow/choose to eat?
market forces determine supply and demand, and farmers grow what is in demand, which increases supply so the prices fall and they stop growing it
What is the average amount of calories of food available each day for every human on the planet?
2,790 calories
What percent higher is the average amount of calories of food available each day for every human on the planet than in 1961?
23%
What has allowed food supply to outpace population growth?
technology
At what capacity are people beginning to doubt if we can feed the world?
9 billion
pest
any species plant, animal, or insect that competes with us for food/resources
What do organisms, such as spiders, sometimes provide for us?
natural pest control
pesticides
chemicals that kill/repel pests
persistence
the amount of time a chemical remains deadly in the environment
Approximately how many people become ill from household pesticides each year?
more than 250,000 people
What effect did DDT have on the bald eagle population?
DDT made the bald eagle population decrease due to the thinning of its egg shells
broad spectrum agents
pesticides that are effective against many species
narrow spectrum agents
pesticides that are effective against more selective species
What is an example of a broad spectrum pesticide?
DDT
What are 3 advantages to pesticides?
- saves lives
- increases food supplies
- work fast
What are 5 disadvantages of pesticides?
- promotes genetic resistance
- kills natural pest enemies
- creates new pest species
- pollutes the environment
- can harm wildlife and people
What are 4 characteristics of the ideal pesticide?
- kills only the target pest
- does not cause genetic resistance in the target organism
- does not pollute the environment by disappearing or breaking down into harmless chemicals after doing its job
- be more cost-effective than doing nothing
What are 4 characteristics of superpests?
- eat many types of plants
- few natural predators
- genetically resistant to many pesticides
- short generation time
What percent of active ingredients in pesticides has the EPA evaluated?
10%
FIFRA (Federal Insecticide, Fungicide, and Rodenticide Act)
regulates the sales, distribution and use of pesticide
1996 Food Quality Protection Act
amended FIFRA by collecting pesticide residue data on commodities most frequently consumed by infants and children and by doing a complete reassessment on all existing pesticide tolerances.
Only what percent of sprayed insecticide reaches the target pest?
0.1-2%
What percent of herbicides reaches weeds?
less than 5%
Where do the pesticides go that do not reach its target organism?
the air, water, non-target organisms, and humans/wildlife
first generation pesticides
made from plants in the 1600s
second generation pesticides
made synthetically, in a lab, from 1939-today
What are 2 other ways to control pests aside from pesticides?
- biological control
- genetic engineering
What is an example of biological pest control?
a wasp parasitizing a gypsy moth caterpillar
How can genetic engineering be used to control pests?
genetic engineering can be used to develop pest and disease resistant crop strains
IPM (Integrated Pest Management)
uses a combination of biological, cultivation, and chemical approaches to pest management
What are 4 drawbacks to IPM?
- not enough experts
- initial costs are high
- situation specific
- not fast acting
What are 4 examples of IPM?
- large vacuums
- a little insecticide as a last resort
- no broad spectrum pesticides
- protect predators of pest species
“100% organic”
no synthetic fertilizer, no pesticides, growth hormones, genetic engineering, or antibiotics
“organic”
means 95% of the ingredients are organic
“made with organic ingredients”
means 70% of the ingredients are organic
organic meat
no hormones, no antibiotics, access to the outdoors, organic fed
How can comparing the relative energy returns from different crops/animals lead inaccurate calculations when measuring energy efficiency?
- The calculation may consider the biomass harvested, not just the biomass that is marketable/edible.
- Is livestock measured by the live weight of the animal or the dressed (just the meat) deadweight?
What are 2 ways we measure the efficiency of a farming system?
- energy contained within the crop of harvested product per unit area
- efficiency of agricultural systems
How is it possible to calculate the efficiency of an agricultural system?
At the end of the system, there is the production of marketable product that is usually sold by weight; therefore, it is possible to calculate the energy contained in a food per unit volume (joules per gram).
How do you calculate the energy balance of the farming system?
Calculate the energy it took to produce the food and deliver it to the market; considering the fuel, labor, and energy that was used to prepare the soil, sow the seed, harvest the crop, prepare the appropriately package it for market, then transport it to the market.
What are 3 example of how the quality of energy is different?
- Fats and proteins contain more energy per gram than carbs.
- Eating less meat and fish than cereal will give you the same amount of energy.
- higher energy content foods cost less to transport as it has a lower volume.
grain equivalent
the quantity of grain that would have to be used to produce one kilogram of a given product
Does aquatic or terrestrial food production generally have a higher energy efficiency?
terrestrial
Compare and contrast terrestrial and aquatic food production.
- In terrestrial systems, food is usually harvested at the first or second trophic level, but in aquatic food production, food normally come from higher trophic levels (fish are normally harvested at the 4th trophic level).
- Terrestrial systems can utilize solar energy more efficiently than aquatic systems.
- Terrestrial systems suffer large losses as a result of skeletal waste because bones are not consumed, but due to losses between trophic levels in aquatic systems the energy efficiency of aquatic food production is generally lower.
What are the 3 steps of the Green Revolution?
- Develop and plant monocultures of high yield varieties of key crops such as rice, wheat, and corn.
- produce high yields using large inputs of fertilizer, pesticides, and water.
- increase the number of crops grown on a plot of land (multiple cropping)
When was the First Green Revolution?
1950-1970
When was the Second Green Revolution?
1967-1985
What was the result of the First Green Revolution?
monocultures, large input of pesticides, water, and fertilizers
What was the result of the Second Green Revolution?
plant fast growing/high yield varieties that can grow on less land
Where was the First Green Revolution?
US and Europe
Gene Revolution
the application of bio-technology following the Green Revolution
What might limit raw material needed for future green and gene revolutions?
the loss of variety of genetically different crop and livestock strains
What percent of food plant varieties available in the 1940s no longer exist in large quantities?
97%
What are 4 things we can do to improve sustainability of food supplies?
- maximize yield
- reduce food waste
- monitoring and control
- change our attitudes towards food and our diets
What are 3 things that allow us to maximize the yield of food production systems?
- improve technology
- alter what we grow
- a new Green Revolution
agroecology
application of ecological principles to agriculture
How have we improved technology of agriculture in the past? (5 examples)
- mixed cropping/interplanting
- no plow tillage (no till farming)
- buffer zones to absorb run off
- IPM
- drip/trickle irrigation
How have we altered what we grow and how we grow agriculture in the past? (3 ways)
- GMOs
- aquaculture/hydroponics
- soil conservation measures
Where is most food wasted in LEDCs?
production and storage
Where is most food wasted in MEDCs?
consumption
What are 2 specific ways MEDCs waste food?
- buying more food than needed
- throwing away edible but “ugly” food
What are 4 specific ways LEDCs waste food?
- pests
- severe weather
- lack of refrigeration
- no canning factory nearby
How have we monitored and controlled the production of agriculture in the past? (2 ways)
- governmental and intergovernmental bodies regulate imports and exports to reduce unsustainable agriculture practice
- NGO pressure groups
What are 4 specific ways we can change our attitude towards our food and diets?
- eat different crops
- eat less meat
- improve education about food
- increase consumption of insects
How much of the world’s meat is produced by livestock grazing on grass?
about half
How much of the world’s meat is produced under factory-like conditions, otherwise known as feedlots?
about half
What are 6 advantages to feedlots?
- increased meat production
- higher profits
- less land use
- reduced overgrazing
- reduced soil erosion
- helps protect biodiversity
What are 3 disadvantages to feedlots?
- need large inputs of grain, fish meal, water, and fossil fuels
- concentrate animal wastes that can pollute water
- antibiotics can increase genetic resistance to microbes in humans
How many people does the FAO predict there will be by 2030?
8 billion
According to the FAO, how much will the amount of calories per person increase by 2030?
2,800 to 3,000
According to the FAO, how much will the number of hungry people decrease by 2030?
900 million to 440 million
By 2030, how much more cereal grain will need to be grown?
an extra billion
About how large is the combined area that is classified as having impaired biotic function as a result of soil loss?
the area is about equal to the size of China and India combined
In MEDCs what can climate and intensive agriculture result in?
soil erosion
What percent of ice-free land is affected by soil degradation?
15%
What 2 types of processes lead to soil degradation?
- processes that take away the soil (erosion)
- processes that make the soil less suitable for use
In what conditions does erosion mainly occur?
when there is no vegetation, so wind and water can then take the soil away
What kind of process makes the soil less suitable for use?
various pollutants/pesticides end up in the soil making it useless in the long run (salinization)
What are 3 examples of human activities that lead to soil degradation?
- overgrazing
- deforestation
- unsustainable agriculture
overgrazing
too many animals graze in the same area/animals stay in the same area too long
selective cutting
carefully selecting each tree
strip cutting
cutting trees in rows
clear cutting
removing large areas of trees
How does deforestation lead to erosion in tropical regions?
the leaves of forest trees both deflect and slow down rain, and the roots bind/stabilize soil
What are 6 examples of unsustainable agriculture?
- total removal of crop after harvest
- having uncovered soil between rows
- plowing in the direction of the slope
- excessive pesticides
- excessive irrigation
- monocultures
How do monocultures lead to unsustainable agriculture?
if the same crop is grown, the same nutrients are being depleted, so the soil loses its fertility
How does excessive irrigation lead to unsustainable agriculture?
leads to salinization and erosion
toxification
excessive use of pesticides makes the soil too toxic for future use
What are 3 major types of erosion?
- sheet wash
- gullying
- wind erosion
sheet wash
uniform removal of surface soil; large areas of surface soil are washed away during heavy storm periods and in mountainous areas moving as landslides
gullying
channels develop on hillsides following rainfall, and overtime these channels become deeper and deeper
wind erosion
on drier exposed soils the wind continually removes top soil
What are 6 measures that can be taken to conserve soil and soil nutrients?
- application of soil conditioners
- wind reduction
- soil conserving cultivation techniques
- improved irrigation techniques
- stop plowing marginal lands
- crop rotation
soil conditioner
improves a soil’s physical qualities and fertility
In the past how have farmers countered soil acidification?
by adding crushed lime or chalk to soil
What are the 2 functions of lime?
- increases pH to counter soil acidification
- helps clay particles stick together and act more like sand
terracing
a method to reduce the steepness of slopes by replacing the slope with a series of horizontal terraces separated by walls
contour farming
plowing and cultivating along contour lines, perpendicular to the hillside
strip cropping
different crops are sown in alternate strips to prevent soil erosion
cover crops
fast growing crops that cover the soil
What are 3 examples of soil conserving cultivation techniques?
- strip cropping with cover crops between rows
- terracing
- contour farming
How can farmers reduce the effect of wind?
alternating low and high crips in fields (strip cropping) and planting trees or bushes to shelter fields (alley cropping)
