12.1 Soil and Agriculture
arable– farmable
“Bad word” – DIRT
GQ: What is soil?
Definition of soil
- a complex plant-supporting system made of disintegrated rock, remains, waste of organisms, water, gases, nutrients, and microorganisms.
- renewable/sustainable resource - takes hundreds to thousands of year to make 1 inch of soil
Factors that influence soil formation
- Organisms – earthworms and other burrowing animals aerate the soil and add matter
- Climate- the warmer and wetter and area is the quicker it renews
- Time - hundreds to thousands of years
- Landforms - climates may be different on either side of a landform. Hills and valleys affect exposure to sun wind and rain. Steep slopes promote erosion
- Parent Material (Bedrock)– the bottom rock that erodes to make soil. The rock from which the soil comes from. It has different physical and chemical properties.
- one teaspoon of soil can contain millions of bacteria, fungi, algae, and protists
Soil Formation
Very complex
Plays a key role in succession – especially primary. When parent material (rock) is exposed
Parent Material:
Base geological material in particular location ex – lava, volcanicash, rock deposited from glaciers, sand dunes, bedrock (solid rick that makes up Earth’s crust), sedimentsdeposited by rivers
Processes that from soil: weathering, depositions, and decomposition
Weathering
Physical and chemical processes that break down rocks and minerals into smaller pieces
Physical – anything touching rock ex – wind, rain, temperatures
Chemical – transforming into a different material
Deposition:
Erosion may help from soil in an area by depositing material from another area
Decomposition
-as plants and animals go about daily activities and decompose as they die -> nutrients are put into the soil ex. – leaf litter
- humus: dark, spongy, crumbly mass of material make up of complex organic compounds
Soil Horizons: distinct layers of soil
Soil profile: cross-section of land from surface to bedrock
******************** / Litter Layer
/////////
//////// / Top Soil *
######
###### / Leaching Layer
++++++++
++++++++ / Sub Soil *
Weathered Parent Material *
@@@@@ / Parent Material
- Main General Layers
- few soils contain all 6 layers
- topsoil is what humans use and degrade
Soil Characteristics
Color: dark soils are rich in nutrients
Texture (particles): Clay particles (small)
Silt
Sand (largest)
- Loam - even mixture of particle sizes
- texture influences workability; silty or loamy are the best
Structure: arrangement of soil particles; clumpy is the best
pH: affects the ability to support plant growth; few plants grow in the extremes
12.2 Dust Bowl
Biggest ecological disaster in America:man-made: mid-west: 1930’s (lasted a decade)
Things that led to Dust Bowl
Overharvesting of soil
Climate of area-windy
State fovernment push to farm
Great Depression – farm for $
Cutting down trees and grass that hold soil in place
Rabbit and locust plagues
Drought
Why would eastern US care?
Provided eastern US with a lot of food, especially wheat
Why do we care today?
We have a world food shortage and we could have one again if we are not smart about our agricultural practices
12.2 Soil Degradation and Conservation
Weathering and Erosion
Weathering breaks down rocks(earths crust) and erosion moves the particles
Causes of erosion
Glaciers (ice)
Wind
Water
Chemicals
Biological (organisms)
Temperature
Sand
Erosion
a natural process, but humans are speeding it up and the crust is not sustainable enough. It occurs all the time.
Degradation
destroying the soil
Intercropping
mixing crops (plants) – keeps nutrients in soil, harvest more, slows process of erosion, and protects from pests
Crop rotation
Alternate crops every few seasons to replenish soil Ex. crops - soybeans and alfalfa (put nutrients back in the soil) it is good thing
Shelter belts and windbreaks
tree lined fields to protest from wind and erosion
Tilling
turning over the litter layer and topsoil why? To bring nutrients to the top getting fresh soil to the top, loosening the soil
Terracing
making steps into the side of a mountain provides flat ground to grew plants on and provides more surface area
Contour farming
plowing sideways across a hillside. Helps with runoff
Over grazing
ranchers allow animals to eat all the vegetation
Clear cutting
completely wipe out all the vegetation in the area, cutting down all the vegetation in your path for logs.
Desertification
making an area of soil nutrient less
Salinization
salt buildup
Pesticide
if we overuse them it is bad . if we use them in the proper quantities it is ok. Chemical s the rid crops of pests
12.2
Pests
Organism that eats/destroys valuable crops
Chemical pesticides
Thousands of chemicals
“evolutionary arms race” – pests adapting
Biological Pest Control
Bring in predator of pest
Pollinator
Fertilize crops
Ex – bees, birds, insects, bat
Problem: there is a decrease in pollinators causing a decrease in crops (some farmers depend on these pollinators for their crops)
US Policies:
- Soil Conservation Service (1935) – the government worked with farmers to develop a conservation plan for farms
- This agency eventually became the Natural Resource Conservation Service – they look at soil, water, pollution amount
- Government give subsidies if a farmer has adopted a conservation plan
- The government pays farmers not to plant on eroding soil - $1 = 1 ton of topsoil saved
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Traditional – Started in the 1800’s. Crops were harvested and stored by using mand and animal ower. Organic fertilizer and irrigation systems were used.
Industrial – machines were masde to make it easier for it to afarm, powered by fossil fuels, and manufactured chemicals
Green Revolution – Late 190’s. The desire for more and better food for the world, agricultural science introduced new technology
12.4 Food production
GQ: How can we produce enough food for a rapidly growing population while sustaining our ability to produce it
Eachyear Earth gains 75 million people and loses 12-17 million acres
Arable land: land suitable for farming (we are using most and people are still starving)
Food security: guarantee of an adequate and reliable food supply for all people at all times
Malnutrition: (underlying factor = $) shortage of nutrients the body needs – this causes diseases
3 essential steps to global food security
1)maintaining healthy soil and H2O
2)protecting biodiversity of food sources
3)ensuring safe distribution of food
Industrial food production: (+) and (-) effects
ex. – feed lots and aquaculture
Feed lot: # of animals raised for food rose fro 7.2 billion to 24.3 billion between 1961-2007
Growth is a cause and effect of industrial agriculture
Feedlot – concentrated animal feeding poerations or factory farms-huge warehouses or pens designed to dleliver energy-rich food to animals
(+)
- efficient production of food
- don’t degrade soil through overgrazing
- reduce need for chemical fertilizers because cow manure is used intead
(-)
- improper management can cause iollness in amnimals and humand
- croweded, dirty conditions cause animals to be pumped with antibiotics wwhich make it into people and ground water to affect ecosystems
- bacterial become resistant to antibiotics
- treatment of aniamals infeedlots (densely packed and cannot interact)
EPA and State agencies regulate feedlots
Aquaculture: raising aquatic food organisms for food in acontrolled environment
(-)
- diseases spread
- waste pollutes outside H2O
- escaped organisms may spread disease to wild animals
- out compete wild animals in genetic modifications
(+)
- reliableprotein source
- sustainable (scraps=fertilizer)
- reduces harvesting of wild animals
- reduces by-catch
- uses less fossil fuel than fishing vessels
- safer work environment
Seed Banks:
- Organizations that preserve seed of diverse plants as a kind of insurance policy against global crop collapse
- Protects diversity
Energy Efficiency:
- Food choices are also energy choices
- procuction of meat for food is extremely inefficient
Pg 381
Ex
Feed inputEdible Weight
20.0 kg1kg - Beef
7.3 kg1 Kg – Pork
4.5 kg1Kg – Chicken
2.8 kg1kg – egg
1.1 kg1kg – milk
Sustainable Agriculture:
Alternative s to industrial agriculture
Agriculture that does not deplete soil faster than it forms and does not reduce soil quality
Organic Agriculture:
Food growing practices that use no synthetic fertilizers, insecticides, fungicidem or herbicides
Organic Food Production Act – established standards for growing and selling
Why people choose organic?
Pesticides may pose health risks
Protect land, H2O, air, and non-target animals from chemicals
Why not?
$ - money - cost
no major concern about pesticides
Locally supported Agriculture:
The average food product travels at least 1500 miles between farm and shoelf and is usually chemically treated to preserve it
Boost local economy
Decrease carbon footprint
Community Supported Agriculture (CSA) – pay in advance for weekly supply