EEB202H1 Lecture Notes - Lecture 14: Nitrogen Fixation, Soil Fertility, Crop Yield

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Published on 17 Jan 2018
School
UTSG
Department
Ecology & Evolutionary Biology
Course
EEB202H1
Professor
Benefits of the Green Revolution
feeds most of the world
allows global well-being
allows specialization, and does not require us all to be farmers
allows us to eat meat
Social Costs of the Green Revolution
crops and farmers are dependent on inputs (pesticides, herbicides, GMO producers)
o this is expensive
farmers have to rely on the corporations that provide these inputs
poor and small farmers can't afford these inputs and have been pushed off the land and
replaced by large agro-businesses
o rural populations forced to migrate to urban areas as a result
this leads to increase in city population density
Environmental Costs of the Green Revolution
causes climate change
pollutes our water ways
destroys habitats
destroys biodiversity
destroys soil
Fertilizers
o the most important nutrients for maintaining yields are Nitrogen (N), Phosphorus
(P), and Potassium (K)
o used in excess, these nutrients can be pollutants
o many high-yielding crop varieties require high fertilizer inputs to achieve
maximum yields
o in the past 50 years, fertilizer use has increased by 500% (800% increase in
nitrogen)
Without fertilizers, how does N enter the ecosystem? Certain wild plants
are able to extract nitrogen from the air (called "nitrogen fixation") and
release it into ecosystems. An example of this wild plant is the Wild lupine.
This is done in the root in the plant. When the plant has taken up as much
nitrogen as possible, any additional nitrogen will leak into the soil.
Nitrogen saturation decreases soil fertility
Once a plant has used as much N as it can, it won't use anymore.
The extra will accumulate and it can leach into other elements
important to soil fertility out with it. It can liberate aluminum,
which can be toxic to plants and aquatic systems.
Excess nitrogen decreases plant diversity
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