IBESS Topic 5

What is Soil

What is Soil

Weather rock particles, gravel, sand, silt, clay, chalk, and minerals

Humus

Organic matter made from decomposition of living things

Factors that affect soil characteristics

Climate, Organisms, Relief (elevation), Parent Material & Time

Acronym for soil horizons

Octopi and Elephants Bake Chocolate Rocks

O horizon

Litter layer of plant residues in relatively undecomposed form.

A horizon

Top soil, rich in decomposed organic material

E horizon

In this zone iron, clay and calcium, organic compounds, and other soluble compounds are leached out of the soil.

When eluviation is pronounced, a lighter colored "E" subsurface soil horizon is apparent at the base of the "A" horizon.

B horizon

Leached nutrient and mineral accumulates in this zone

C horizon

Layer of large unbroken rocks.

R horizon

Bedrock

Inputs

Organic and parent materials, precipitation, infiltration, energy

Outputs

Leaching, uptake by plants, erosion

Transfers

Deposition (reorganization of soil)

Transformations

Decomposition, weathering, nutrient cycling

Storages

Organic matter, nutrients, organisms, minerals, air & water

Physical Weathering

• Cold, then warm temps

• Windy conditions

• Wet conditions

Chemical Weathering

• Warm temps

• Plenty of organic material

• Wet conditions

Biological Weathering

• Warm temps

• Plenty of organic material

• Lots of sunlight

• Wet conditions

Why are clay soils not ideal for agriculture?

Small particles: fit, space, water

Permeability

Rate at which air and water can flow through the layers in the soil

• Size of spaces in soil determines permeability

Porosity

Measure of how much space between particles

• Fine particles = water retention

• Coarse particles = air retention

• More porous = more water and air

Translocation

Movement of water up or down layer in soil

• Salinization

• Leaching

Why are sand soils not ideal for agriculture?

Large pore space: easily uprooted, water drains easily, cannot hold nutrients

Most productive type of soils

Loamy soils → mix of particle sizes

Tropical rainforest soils are poor because…

• thin O horizons

• little organic input from shed vegetation

• nutrients are leached out or eroded away by heavy rainfall

Causes of Soil Degradation

Human activities:

• deforestation

• overgrazing by raised livestock

• poor farming practices

Case Study: Dust Bowl

• removal of perennial grasses + annually harvested crops = few anchors to prevent erosion

• Appalachian and Rocky Mountain served as walls

Salinization

Poor irrigation practices in arid regions result in salt deposits in topsoil

Compaction

Heavy machinery and animals compact soil creating a denser soil; top soil becomes drier; seeds a prevented from taking root

Soil Conservation Methods

• shelterbelts

• terracing

• contour ploughing

• no till/reduced tilling

• intercropping

• crop rotation

• silt fencing

Shelterbelts

Systematic planting of trees helps to buffer winds and reduce wind erosion

Terracing

Creating stepped plateaus into a steep hillside increases farmable acreage while helping to reduce water erosion

Contour ploughing

Crops are planted perpendicularly to the slope which create physical barriers that help slow down runoff and reduce the amount of soil erosion

No till/reduced tillage

This practice creates less disturbed soil which means less erosion.

Intercropping

Increases total crop yields per acre & roots per area. More roots per year = less erosion

Crop rotation

Rotating a nitrogen fixing crop through the fields increases soil fertility = bigger plants with stronger roots = roots holds onto soil helping to reduce erosion

3 Major Agricultural Revolution

• Hunting and Gathering

• Business (1500’s-1850’s)

• Green Revolution (1950’s-1970’s)

Green Revolution Problem

India: Undernourishment

Green Revolution Solution

Use technology (fertilizers, irrigation, specially bred strains of seed) to increase yield

Commercial agriculture

Large scale production of crops and livestock for sale

Subsistence agriculture

Farming for self-sufficiency to grow enough for a family

Agribusiness

• fossil fuels for mechanized equipment

• water for irrigation

• pesticides for pest control

• fertilizers to produce high yield

Negatives of Agribusiness (many)

• deforestation + biodiversity

• monocultures that are susceptible to failure

• reduction of water availability

Desertification → food insecurity

Process by which a fertile land changes itself into a desert by losing its flora and fauna

In MEDCs food is wasted because

Aesthetic, taste preference, over consumption & misunderstanding (expiration date vs best by date)

In LEDCs food is wasted because

Inadequate protection from bugs/rodents, refrigeration, and spoilage in transit

What shapes our food production systems?

• Climate (availability)

• Cultural/Religious influences (Islam-no pork)

• Policies (tariffs on food)

• Socio-economic (explotation of workers in the search for affordability)

Farming Systems: Subsistence Farming

• food for family

• no surplus

• mixed crops

• cash cropping

Farming Systems: Commercial Farming

• PROFIT!

• maximizing yield

• technology

• monocultures

Farming Systems: Pastoral Farming

Raising animals on grass and land not suitable for crops

Farming Systems: Arable Farming

Growing crops on good soil to eat directly or feed to animals

Making our Food Systems More Sustainable

• Increase consumption of organically grown foods (local and seasonal)

• Polyculture!

• Reduce meat consumption

• Pollution Management (Buffer Zones)

Pest

Any organism that damages crops that are of value

Weed

Any plant that competes with valuable crops

Pesticides

Poisons that target pests

Insecticides

Kill insects

Herbicides

Kill plants

Fungicides

Kill fungi

Bioaccumulation

The gradual accumulation of substances in an organism

Integrated Pest Management (IPM) Systems

Numerous techniques are used in combination to control pests to a manageable level (reduce pests to a tolerable level)