Download - Catalyst

Nutrients in Agriculture
Topics
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Basic plant physiology
Types of nutrients systems
Relation between fertilizer use and production
Amount of fertilizer used
World supply of fertilizer
Fates of fertilizer in the biosphere
Dead zones and associated controversy
Other environmental impacts of fertilizers
Key messages
Plant physiology
Plants must obtain the following
mineral nutrients from the growing
media:[2]
the primary macronutrients:
nitrogen (N), phosphorus (P),
potassium (K)
the three secondary macronutrients
such as calcium (Ca), sulphur (S),
magnesium (Mg).
the macronutrient Silicon (Si)
and micronutrients or trace
minerals: boron (B), chlorine (Cl),
manganese (Mn), iron (Fe), zinc
(Zn), copper (Cu), molybdenum
(Mo), nickel (Ni), selenium (Se), and
sodium (Na).
Types of nutrient systems
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Pre-industrial manure cycles and crop rotation
Organic fertilizers
Industrial Fertilizers
Organic Farming
Medieval European Agriculture
• Plowing done with an ox or horse, harvest by
hand
• Nutrients supplied by animal manure, human
manure and fallowing the ground every 2nd or 3rd
year, sometimes planted with legumes.
• Plowing plants back into the ground to fertilize
the ground is known as “green manure”
• Grain production about 1/5 per ha of current
yields. Yield was about 4 seeds per seed planted.
The Black Death
Agricultural consequences of plague in
Europe
• About 1/3 of people died – human density
reduced
• Price of labor to landlords increased
• More land per person – more land could be
devoted to animals, more manure available,
more fallow and pasture
• Soil building and higher yields
Rice culture
in the past, traditional rice farmers in Asia
used raw organic matter, human and
animal manures, ashes, fish bone and
other waste materials to make the rice
plant more productive. Compost and green
manures had also widely used. Compost
was a major factor for farmers to win in
yield contests organized in Japan during
1948-1968. In many countries green
manure is regarded as an important
nutrient source for rice.
Other sources
• Native Americans used fish
• Seaweed
Natural sources
• Guano
• Phosphate
Guano
Bird droppings rich in phosphate and nitrogen. the US passed the Guano
Islands Act in 1856 giving citizens discovering a source of guano the right to
take possession of unclaimed land and entitlement to exclusive rights to the
deposits.
Phosphate rock
• Many rocks are naturally rich in phosphate
• This can be mined and used as fertilizer
The collapse of Nauru
• Small Island consisting primarily of phosphate
The collapse
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Once called the Kuwait of the Pacific
10,000 people had $1 Billion in assets
Nauru Hotel in Honolulu
Lost it all due to bad financial management
The island is a hollow shell, stripped clean
Ended up taking “boat people” Australia didn’t
want in order to get some funds
Artificial fertilizer
History
• Haber and Bosch were awarded the Nobel
Prize for method to produce industrial
ammonia from atmospheric nitrogen and
natural gas.
• This process forms the basis for almost all
industrial nitrogen fertilizers, uses 1-2% of
world energy supply
• Rock based phosphates are often added in
modern fertilizer
Global supply
The Phosphate Famine
Environmental Impacts
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Eutrophication
Soil acidification
Persistent organic pollutants
Heavy metal accumulation
Radioactive element accumulation
From farm to water
• 20% lost through surface runoff and leaching
• Volatilization is transfer of nitrogen to the air
from crops and manure, and this nitrogen is
subsequently deposited on land and water
Gulf of Mexico Dead Zone
What is a dead zone: Gulf of Mexico
• An seasonal or permanent zone of low oxygen
concentration
• Caused by bacterial action consuming the
available oxygen
• Nitrogen and phosphorus come almost
exclusively from river discharge which have
increased 3 fold for phosphorus and 8 fold for
nitrogen compared to pre-industrial inputs
Other dead zones
• Often natural caused by changes in ocean
circulation through upwelling
Small group discussion
• What could be done to reduce the dead zones
in the Gulf of Mexico
• Who would do it?
Soil acidification
• Some soils are naturally acidic
• Many fertilizers increase soil acidity, reducing
productivity for many crops
• Adding lime is a common remedy for acid soils
Persistent organic pollutants
• Organic chemicals that are resistant to
degradation
• They are found in some fertilizers and
accumulate in the soils can health impacts in
high concentrations
Heavy metal accumulation
• A number of fertilizers have trace amounts of
heavy metals such as cadmium, zinc, lead and
arsenic
• This do not degrade and accumulate
Radioactive element accumulation
• Some phosphate fertilizers contain radioactive
uranium, that accumulate in soils
Nutrients in organic farming
• Compost
• Crop rotation
• Cover crops of legumes that are plowed back
(called green manure)
• Animal manure
Key messages
• Nutrients are essential to food production
• Increase in yields has been significantly due to
added inputs of nutrients
• These nutrients have significant
environmental impacts
• Human health impacts always need to be
balanced against the benefits of higher yields
Study guide
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What are the three primary macronutrients needed for plant growth?
Nitrogen, phosphorus and potassium
What were the major sources of nutrients in pre-industrial European agriculture?
Animal manure, human manure, green manure.
What was the major impact of the Black Death on European agriculture?
Population density was reduced so that there was more land available for animals, leading to more manure, leading to higher crop yields and soil
building.
What are two natural forms of industrial scale fertilizer.
Bird guano and natural phosphate deposits.
What is the role of the nation of Nauru in agriculture?
It was once the source of rich phosphate deposits.
What was the major scientific discovery that stimulated the modern fertilizer industry?
The development of the Haber-Bosch process for converting atmospheric nitrogen and natural gas to ammonia.
What are the major concerns about the impact of artificial fertilizers on the environment and soils?
Eutrophication
Soil acidification
Persistent organic pollutants
Heavy metal accumulation
Radioactive element accumulation
What is volatilization?
Volatilization is transfer of nitrogen to the air from crops and manure, and this nitrogen is subsequently deposited on land and water.
What is a dead zone?
A region of the ocean with very low oxygen concentration.
How do fertilizers contribute to soil acidification?
Many fertilizers are naturally acidic making the soil more acidic.