HENVI SEMINAR SERIES
The role and future of nitrogen fixation
Kristina Lindström
30.10.2013
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Kristina Lindström: 30.10..2013
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THE NITROGEN CYCLE IS MAINLY
DRIVEN BY MICROBES
AMMONIFICATION
NITRIFICATION
DENITRIFICATION
BIOLOGICAL NITROGEN FIXATION
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ELECTRONS REMOVED
ELECTRONS ADDED
Annual Reviews
THE NITROGEN CYCLE IS MAINLY
DRIVEN BY MICROBES
AMMONIFICATION
ORGANIC MATERIAL IS BROKEN DOWN BY MICROBIAL
ENZYMES TO END UP AS AMMONIA (NH3) OR
AMMONIUM (NH4+)
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AMMONIFICATION
Annual Reviews
THE NITROGEN CYCLE IS MAINLY
DRIVEN BY MICROBES
AMMONIFICATION
NITRIFICATION Bacteria (AOB) and Archaea (AOA)
use nitrate as a source of energy, which is used for
maintenance (ATP, reducing power) and biosyntheses
through CO2 reduction.
Thus, there is a connection between the N and the C cycles.
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NITRIFICATION
Annual Reviews
RISKS WITH NITRIFICATION
NITRATE LEACHING
DENITRIFICATION
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A CONNECTION BETWEEN N AND
C CYCLES
AMMONIFICATION
NITRIFICATION
DENITRIFICATION Microbes use nitrate as their
alternative/facultative terminal electron acceptor in
anaerobic respiration.
Performed by a large variety of bacteria and even fungi.
Kristina Lindström: 30.10..2013
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DENITRIFICATION
Annual Reviews
THE NITROGEN CYCLE IS MAINLY
DRIVEN BY MICROBES
AMMONIFICATION
NITRIFICATION
DENITRIFICATION
BIOLOGICAL NITROGEN FIXATION
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DENITRIFICATION
REMOVES N FROM THE ECOSYSTEM INTO
THE ATMOSPHERE
N2O IS A POTENT GREENHOUSE GAS
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BIOLOGICAL NITROGEN FIXATION
N2 + H2 + 16ATP -> 2NH3 + H2
SOME MICROORGANISMS CAN REDUCE ATMOSPHERIC
DINITROGEN GAS TO AMMONIA
THE RESPONSIBLE ENZYME IS NITROGENASE
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NITROGEN FIXATION
Annual Reviews
BIOLOGICAL NITROGEN FIXATION
N2 + H2 + 16ATP -> 2NH3 + H2
LEGUMES ARE THE MOST IMPORTANT TERRESTRIAL
NITROGEN FIXERS
NITROGEN FIXATION
IN OCEANS HARD TO ESTIMATE
SYMBIOTIC NITROGEN FIXATION
IN BOREAL FORESTS?
Kristina Lindström: 30.10..2013
IN MOSSES IMPORTANT
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HUMAN INTERVENTION
INDUSTRIAL FIXATION 140 TgN/year
BIOLOGICAL FIXATION 110 TgN/year
- Human contribution also through cultivation
of legumes and burning fossil fuels
- Anthropogenic sources approach half of the
estimated global nitrogen fixation
(Canfield et al. 2010)
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RISKS?
EUTROPHICATION – LEACHING OF N AND
PHOSPHOROUS LEADING TO ALGAL BLOOMS
N FIXING CYANOBACTERIA
DENITRIFICATION TO N2O
SOIL EROSION AND NUTRIENT LOSSES
ROCKSTRÖM
Kristina Lindström: 30.10..2013
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Rockström et al. (2009)
RISKS?
THE NITROGEN CAN ESCAPE
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Rockström et al. (2009)
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HOW TO FERTILIZE
WISELY?
THE NITROGEN FACTORY
REQUIRES 1.5 KG OIL PER
1 KG NITROGEN FERTILIZER
THE HABER-BOSCH-REACTION
REQUIRES HIGH PRESSURE
AND HIGH TEMPERATURES
IN THE FIELD THE
ENERGY SOURCE IS
BIOLOGICAL ENERGY
(ATP, REDUCING POWER)
WHICH ORIGINATES IN
SOLAR ENERGY IS USED
THE NODULES FUNCTION
AT NORMAL PRESSURE
AND TEMPERATURE,
EVEN CLOSE TO ZERO
DEGREES
NITROGENASE
Cheezeworld.com
Kristina Lindström 30.10.2013
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THE LEGUME – RHIZOBIUM SYMBIOSIS
Photosynthesis
CO2
CO2
Carbon
compounds
ROOT NODUES
Nitrogen
compounds
N2
BACTERIA
Symbiotic nitrogen fixation
N2
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REPLACING MINERAL N FERTILIZER
WITH LEGUME N
THE CLOVER RHIZOBIA CAN
FIX N FROM THE ATMOSPHERE
TO SATISFY ALL THE N NEEDS
OF THE HOST PLANT
Red clover is essential in
Finnish organic agriculture
ABOUT 100 KG N PER HARVEST
AND HECTARE
TO AVOID N LOSSES LEGUMES
SHOULD BE CULTIVATED IN
MIXES WITH OTHER CROPS,
SUCH AS GRASSES
Kristina Lindström 30.10.2013
Kortjärvi Byagårdsförening r.f.
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LEGUMES ARE IMPORTANT
PROTEIN SOURCES
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LEGUMINOUS TREES ON THE SAVANNAH IN
NATURAL ECOSYSTEMS IN BALANCE
Kristina Lindström: De fantastiska rhizobierna
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ETHIOPIA:
AT THE BEGINNING OF THE 18TH CENTURY 40% OF THE LAND AREA (1 Mha)
WAS COVERED BY FOREST.TODAY ONLY 4%
>50% of the population malourished before 2000,
Since then 35-50% (FAO)
4% of the land is not destroyed
10% lightly destroyed
57% moderately destroyed
Main reason: Over grazing leading to water erosion
(FAO TERRASTAT)
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INOCULATION OF LEGUME SEED
WITH SUITABLE
RHIZOBIA
UNINOCULATED
INOCULATED
INOCULATION IS ONE OF THE
OLDEST AGRO-BIOTECHNOLOGICAL APPLICATIONS
Kristina Lindström 10.1.2013
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FIGHTING EROSION,
A VILLAGE PROJECT
PLANTING LEGUMINOUS TREES
CONSTRUCTION OF
TERRACES
Kristina Lindström: 10.1.2013
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TWO YEARS LATER:
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LEGUME TREES GROWN WITH
ENSET, COFFEE AND MAIZE
LEARN FROM EACH OTHER:
SUSTAINABLE AGRICULTURE IN DILLA, ETHIOPIA
TRADITIONAL AGROFORESTRY
Kristina Lindström 10.1.2013
PARKLAND AGROFORESTRY IN
OROMIA, ETHIOPIA
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SUGGESTED LITERATURE
Canfield DE, Glazer AN, Falkowski PG. 2010. The evolution and
future of Earth’s nitrogen cycle. Science 330:192–96.
Lindström K, Mousavi SA. 2010. (November 2010)
Rhizobium and Other N-fixing Symbioses. In: Encyclopedia of Life
Sciences (ELS). John Wiley & Sons, Ltd: Chichester.
DOI: 10.1002/9780470015902.a0021157
Rockström J. et al. 2009. A safe operating space for humanity. Nature
461: 472-475.
Thamdrup B. 2012. New Pathways and Processes in the global
Nitrogen cycle. Annu. Rev. Ecol. Evol. Syst.. 43:407–28
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