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Lecture

Class 12 - Soil & Food.docx


Department
Environmental Studies
Course Code
ENV 1101
Professor
Sonia Wesche

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Soil & Food
Food Security
The 5 A‟s of food security
o Availability
o Affordability
o Accessibility
o Acceptability
o Adequacy
Food Production not the real (current) problem
Keeping Up With Population Growth: The Green Revolution
1940‟s – 1960‟s and beyond
Transfer of technologies to developing nations
o Heavy equip, chemical pesticides, synthetic fertilizers, irrigation
Introduction of high yield hybrid varieties (HYVs) wheat, rice, corn
o Intensification (vs. extensification)
Still going on:
o Development of new crops; pest resistance; expansion into other regions
o Population growth 2%/year, wheat and rice 4%/year (up to mid 80‟s)
Threats to Food Security
Soil Degradation
Changing diets
Food to energy
Climate change
Technology: new problems
Conflict, Politics & Policies
Threats to Food Security: Soil Degradation
90% of the world‟s food from land-based agriculture
o 38% of land surface dedicated to agriculture
Maintenance of soil = cornerstone of civilizations
What is Soil?
A mixture (system) of organic material, inorganic material, and living organisms
Soil Availability
Some places have lots of good soil, other may have none at all
Soil if Fragile
It takes decades or more to form a few inches of soil
Soil can be removed from poorly managed land in a single season
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Important Characteristics
Larger soil particles have larger spaces between them (are more porous)
Smaller particles have a greater proportion of surface are relative to volume
Water and nutrients tend to cling to surfaces
Soil Quality
For agricultural production, a soil containing a mixture of particle sizes is
desirable
Ensures availability of nutrients, ability to hold water and is workable
Compacted soil lacks pore space for movement of water, air
What Makes Soil Fertile?
Availability of nutrients, minerals (P, K, Ca)
Ability to hold water (but not too much)
Aeration
pH near neutral (i.e. neither especially acid nor alkaline)
Minimal amount of salt
Organisms in the Soil
Break down organic material on surface, creating humus
Create concentrated particles containing mixtures of humus/minerals
Improve soil structure (make it nice and loose)
Some bacteria draw nutrients to plant roots
Not all are helpful (ex. nematodes)
Soil Degradation
Erosion
Desertification
Erosion: Human Factors
Removal of vegetative cover (deforestation)
Over-cultivation
Irrigation
Overgrazing
Causes of Soil Degradation
Removal of vegetative cover (deforestation)
Removal of vegetative cover for construction
Too much plowing (over-cultivation)
Nutrient exhaustion from monoculture
Over-irrigation leads to salinization
Overgrazing
Erosion: Associated Problems
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