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

  1. Organisms – earthworms and other burrowing animals aerate the soil and add matter
  2. Climate- the warmer and wetter and area is the quicker it renews
  3. Time - hundreds to thousands of years
  4. 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
  5. 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