Imprint of management on microbial communities in arable soil: implications for N2O emissions

Tina Putz

Imprint of management on microbial communities in arable soil: implications for N2O emissions

Tina Putz

Institutionen för skoglig mykologi och växtpatologi

Publikation: Avhandling › Doktorsavhandling

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Sammanfattning

Jordbruksmark är den enskilt största källan av växthusgasen lustgas, vilket är direkt kopplat till det ökade användandet av kvävegödsel. Mikrobsamhällen i marken avgör vad som händer med tillsatt kväve och styr lustgasproduktionen. Under syrefria förhållanden påverkas nitrat i marken av två processer: denitrifikation, som stegvis omvandlar nitrat till lustgas eller till atmosfäriskt kväve, och dissimilatorisk nitratreduktion till ammonium (DNRA), som omvandlar det till ammonium. Denitrifierande bakterier, och icke - denitrifierande lustgasreducerande bakterier, är den enda kända biologiska lustgassänkan. Syftet med denna avhandling var att undersöka hur brukandet av jorden påverkar mångfalden, strukturen och aktiviteten hos de marklevande mikroorganismer som reglerar de dominerande anaeroba kväveomvandlingsprocesserna i mark, och därigenom lustgasproduktionen. Hypotesen var att kväverika förhållanden och långvarig gödsling gynnar icke fullständiga denitrifierare, medan kolrika förhållanden ökar mängden DNRA-bakterier och lustgasreducerande organismer, vilket stärker jordens lustgassänkande kapacitet. Vi inokulerade jord med icke denitrifierande lustgasreducerande bakterier, vilket bekräftar ett samband mellan antalet lustgasrducerande bakterier och minskad lustgasproduktionen. I en studie med långliggande gödslingförsök fann vi att kvävegödsling konsekvent ökade förekomsten av organismer med genetiska förutsättningar för att både producera och konsumera lustgas. Trots detta dominerades jordarna av ofullständigt denitrifierande organismer, vilket leder till ökad potential för lustgasproduktion. En annan fältstudie med gödsling i växtföljder med och utan vall indikerade att växtföljden orsakar förändringar i jordens kol-kväve-förhållande, vilket påverkar balansen mellan DNRA och denitrifikation: högre kol-kväve-kvot ger mer DNRA och ett mikrobsamhälle med bättre förmåga att reducera lustgas. Detta bekräftades i kontrollerade försök där kol-kväve-förhållandet i olika jordar manipulerades.

Originalspråk	Engelska
Kvalifikation	Doktor i filosofi
Förlag	Swedish University of Agricultural Sciences
Tryckta ISBN	978-91-7760-210-1
Elektroniska ISBN	978-91-7760-211-8
Status	Publicerad - 2018

Nyckelord

C:N ratio
DNRA
arable soil
denitrification
fertilization
microbial communities
nitrous oxide

SLU-serie

Acta Universitatis Agriculturae Sueciae

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@phdthesis{bea5e6f37fed482c9c1ee25026d66e19,

title = "Imprint of management on microbial communities in arable soil: implications for N2O emissions",

abstract = "Arable soils are a major source of the greenhouse gas nitrous oxide (N2O), emissions of which are directly linked to increased use of N fertilizers. Microbial communities that drive N cycle processes in soil ultimately determine the fate of reactive N inputs and control N2O emissions. Under anoxic conditions, two processes compete for nitrate (NO3-): denitrification, the stepwise reduction of NO3- to N2O or atmospheric nitrogen, and dissimilatory nitrate reduction to ammonium (DNRA), in which NO3- is reduced to ammonium (NH4+). The reduction of N2O by denitrifiers and non-denitrifying N2O reducers is the only known biological sink for N2O. The aim of this thesis was to investigate how edaphic factors that are altered by soil management practices influence the diversity, structure and activity of the soil microbiota regulating anaerobic N cycling, and thereby N2O emissions. We hypothesised that N replete conditions and long-term fertilization promote incomplete denitrifiers, whereas high C content increases the abundance of DNRA bacteria and N2O reducing organisms, enhancing soil N2O sink capacity. Inoculation of soil microcosms with a non-denitrifying N2O reducing strain confirmed that increased abundance of these organisms can mitigate soil N2O emissions. A survey of long-term fertilization trials showed a consistent increase in the relative abundance of taxonomic groups previously inferred from genomic evidence to produce or consume N2O in fertilized soil. Nevertheless, the abundance of organisms comprising a truncated denitrification remained dominant, concomitant with increased potential N2O emissions. Another field study including fertilization and different crop rotations suggested that changes in soil C/N ratio due to cropping system influenced the competition between DNRA and denitrification, with higher C/N promoting DNRA and N2O reducing community abundance and activity. This was confirmed in controlled manipulations of C/N in a microcosm study, suggesting that soils covering higher C/N ratios sustain a greater abundance of DNRA and N2O reducing bacteria and therefore have a lower N2O emission potential.",

keywords = "C:N ratio, DNRA, arable soil, denitrification, fertilization, microbial communities, nitrous oxide, C:N ratio, DNRA, arable soil, denitrification, fertilization, microbial communities, nitrous oxide",

author = "Tina Putz",

year = "2018",

language = "English",

isbn = "978-91-7760-210-1",

series = "Acta Universitatis Agriculturae Sueciae",

publisher = "Swedish University of Agricultural Sciences",

number = "2018:35",

address = "Sweden",

}

TY - BOOK

T1 - Imprint of management on microbial communities in arable soil

T2 - implications for N2O emissions

AU - Putz, Tina

PY - 2018

Y1 - 2018

N2 - Arable soils are a major source of the greenhouse gas nitrous oxide (N2O), emissions of which are directly linked to increased use of N fertilizers. Microbial communities that drive N cycle processes in soil ultimately determine the fate of reactive N inputs and control N2O emissions. Under anoxic conditions, two processes compete for nitrate (NO3-): denitrification, the stepwise reduction of NO3- to N2O or atmospheric nitrogen, and dissimilatory nitrate reduction to ammonium (DNRA), in which NO3- is reduced to ammonium (NH4+). The reduction of N2O by denitrifiers and non-denitrifying N2O reducers is the only known biological sink for N2O. The aim of this thesis was to investigate how edaphic factors that are altered by soil management practices influence the diversity, structure and activity of the soil microbiota regulating anaerobic N cycling, and thereby N2O emissions. We hypothesised that N replete conditions and long-term fertilization promote incomplete denitrifiers, whereas high C content increases the abundance of DNRA bacteria and N2O reducing organisms, enhancing soil N2O sink capacity. Inoculation of soil microcosms with a non-denitrifying N2O reducing strain confirmed that increased abundance of these organisms can mitigate soil N2O emissions. A survey of long-term fertilization trials showed a consistent increase in the relative abundance of taxonomic groups previously inferred from genomic evidence to produce or consume N2O in fertilized soil. Nevertheless, the abundance of organisms comprising a truncated denitrification remained dominant, concomitant with increased potential N2O emissions. Another field study including fertilization and different crop rotations suggested that changes in soil C/N ratio due to cropping system influenced the competition between DNRA and denitrification, with higher C/N promoting DNRA and N2O reducing community abundance and activity. This was confirmed in controlled manipulations of C/N in a microcosm study, suggesting that soils covering higher C/N ratios sustain a greater abundance of DNRA and N2O reducing bacteria and therefore have a lower N2O emission potential.

AB - Arable soils are a major source of the greenhouse gas nitrous oxide (N2O), emissions of which are directly linked to increased use of N fertilizers. Microbial communities that drive N cycle processes in soil ultimately determine the fate of reactive N inputs and control N2O emissions. Under anoxic conditions, two processes compete for nitrate (NO3-): denitrification, the stepwise reduction of NO3- to N2O or atmospheric nitrogen, and dissimilatory nitrate reduction to ammonium (DNRA), in which NO3- is reduced to ammonium (NH4+). The reduction of N2O by denitrifiers and non-denitrifying N2O reducers is the only known biological sink for N2O. The aim of this thesis was to investigate how edaphic factors that are altered by soil management practices influence the diversity, structure and activity of the soil microbiota regulating anaerobic N cycling, and thereby N2O emissions. We hypothesised that N replete conditions and long-term fertilization promote incomplete denitrifiers, whereas high C content increases the abundance of DNRA bacteria and N2O reducing organisms, enhancing soil N2O sink capacity. Inoculation of soil microcosms with a non-denitrifying N2O reducing strain confirmed that increased abundance of these organisms can mitigate soil N2O emissions. A survey of long-term fertilization trials showed a consistent increase in the relative abundance of taxonomic groups previously inferred from genomic evidence to produce or consume N2O in fertilized soil. Nevertheless, the abundance of organisms comprising a truncated denitrification remained dominant, concomitant with increased potential N2O emissions. Another field study including fertilization and different crop rotations suggested that changes in soil C/N ratio due to cropping system influenced the competition between DNRA and denitrification, with higher C/N promoting DNRA and N2O reducing community abundance and activity. This was confirmed in controlled manipulations of C/N in a microcosm study, suggesting that soils covering higher C/N ratios sustain a greater abundance of DNRA and N2O reducing bacteria and therefore have a lower N2O emission potential.

KW - C:N ratio

KW - DNRA

KW - arable soil

KW - denitrification

KW - fertilization

KW - microbial communities

KW - nitrous oxide

KW - C:N ratio

KW - DNRA

KW - arable soil

KW - denitrification

KW - fertilization

KW - microbial communities

KW - nitrous oxide

UR - https://res.slu.se/id/publ/104198

M3 - Doctoral thesis

SN - 978-91-7760-210-1

T3 - Acta Universitatis Agriculturae Sueciae

PB - Swedish University of Agricultural Sciences

ER -