CLIENT IIDEU
Austrian Academy of SciencesVienna, February 27, 2019
NitrogenA cross-cutting environmental challenge
Agricultural soils influenced by theinterplay between carbon and nitrogen
Georg Guggenberger
Leibniz Universität HannoverInstitute of Soil [email protected]
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Arable soils –Too less carbon – too much reactive nitrogen
OC contents in arable and grassland soils N surplus in agricultural soils
UBA Texte 82/2003Thünen Report 64 (2018) – provided by Axel Don
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Points of discussion
• Development of OC and N stocks in arable soils(of Germany)
• Effects of N fertilization on OC contents and N emission
• Sources of N emissions from soil(can there be too much ‚humus‘?)
• N- und soil management with catch crops(Catchy)
• Final thoughts
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Development of OC and N stocks
Grassland Arable field
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Variables for OC and N contents
Thünen Report 64 (2018) – zur Verfügung gestellt von Axel Don
Climate
Land use /management
Site conditions(Texture, parentmaterial, etc.)
Explained variance (%)
R2=0.46
R2=0.38
Land useGround water distance
Clay contentsHorizon enriched in C
Parent materialMean annual precipitation
StratigraphyParent material
Horizon enriched in CSand contentsClay contentsRoot biomass
Relative importanceof variables (%)Thünen Report 64 (2018) –
provided by Axel Don
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OC stocks in different soil types
Thünen Report 64 (2018) – provided by Axel Don
Pararendzina
13,4 t ORegosol
65,1 t OCParabraunerde
78,4 t OCPseudogley
82,1 t OCHumusgley
131,7 t OCErdniedermoor
693,7 t OC
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Relation between clay contents and OC contents
Impact of texture
Clay content influences regional differences in OC stocks
Thünen Report 64 (2018) –provided by Axel Don
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OC contents in arable and grassland soils
Impact of land use
Thünen Report 64 (2018) – zur Verfügung gestellt von Axel Don
OC stocks in arable an grassland soils
Arable soils store 30-40% less OC than grassland soils
Land use depends on site conditionsThünen Report 64 (2018) –provided by Axel Don
Topsoil Subsoil
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Effects of land use change worldwide
Changes in OC stocks
Guo und Clifford (2002) GBC
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C/N ratios in arable and grassland soils
C/N ratios
C/N ratios in soil independent ofC/N ratios of litter
Hint for microbial residues
In grassland soil higher rootresidue input to subsoil
N losses due to arable land use
Thünen Report 64 (2018) – provided by Axel Don
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Impact of land use history on OC stocks
in Oberboden (0-30 cm, dunkel) und Unterboden (30-100 cm, hell)
OC
sto
cks
(t h
a-1)
Topsoil
Subsoil
Impact of plowingof grassland after decades
OC is not in steadystate equilibrium
OC
sto
cks
(t h
a-1)
Thünen Report 64 (2018) –provided by Axel Don
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Effects of N fertilization on OC contentsand N emission
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OC stocks related to N fertilization
Düngung
ohneNPK
10 t/ha a
10 t/ha a
+ N
PK
15 t/ha a
15 t/ha a
+ N
PK
Corg
[%
]
0.0
0.5
1.0
1.5
2.0
2.5
Nt (%
)
0.00
0.05
0.10
0.15
0.20
0.25
Corg (%)
Nt (%)
Col 4
Col 5
Körschens und Pfefferkorn (1998) Der Statische Düngungsversuch Bad Lauchstädt (Hrsg. UFZ)
Example Bad Lauchstädt
It was argued to be due to a higher NPP and a higher returnof crop residues to soil
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Relation between N fertilization and C sequestrationrate (SCSR) in two regions of China
Lu et al. (2009) GCB
Relation between N fertilization and C sequestration
III
Relation was interpreted as the result of higher residue input
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Lu et al. (2009) GCB
III
Plea for straw return to soil
Relation between straw returned and C sequestration
Relation between amount of straw returned and C sequestration rate (SCSR) in two regions of China
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Kirkby et al. (2014) SBB
Stabilization of straw-derived C without and with fertilization
Influence of straw return and nutrient applicationto net changes of stable C (FF-C, fine fraction C)
Microbial C assimilation works only if nutrients are available
Microbial detritus forms stable organic matter
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Van Groenigenet al. (2006) PNAS
Effect of elevated CO2 concentration onC stocks, root biomass and N2 fixation
Meta analysisbased on 80observations
C contents relatedto N fertilization
Root biomass relatedto N fertilization
N2 fixation relatedto non-N fertilizers
Accumulation of OC due to CO2 fertilization requires nutrients
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Microbial respiraton Microbial C uptake
Spohn et al. (2016) SBB
At N fertilization lower microbial energy demand and likely inhibition of oxidative enzymes
Microbial ‘carbon use efficiency’depending on fertilization
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Microbial ‚carbon use efficiency‘
Spohn et al. (2016) SBB
Lower microbial respiration and C uptakeresults in higher microbial ‚carbon useefficiency‘
Less C is processed intracellularly
N fertilization can increase efficiencyin C cycling
Microbial ‘carbon use efficiency’depending on fertilization
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Xia et al. (2018) GCB
Coming to reactive N – Influence of straw returnand N fertilization on soil parameters
Selected soil parameters from a world-wide data base
Immobilization of N in microbial biomass
Increases urease activity
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Influence of straw return andN fertilization on NH3 and N2O emission
Ausgewählte Parameter einer weltweiten Datenbasis
Xia et al. (2018) GCB
NH3 N2ODenitrification to N2
Higher NH3 emissiondue to urease activity
Narrow C/N ratio:N is available formineralization anddenitrification
Wide C/N ratio:Microbial assimilation
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Relation between N fertilization and N emission from Chinese paddy soils (n=107)
Chen et al. (2014) Nature
Relation between N fertilization and N emission
NH3 emission N2O emission N leaching
Direct relation between N fertilization and N emission(similar at wheat and maize)
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OC enrichment due to N fertilization C sequestration vs. CO2 emission from fertilizer
Poeplau et al. (2018) AGEE
C fluxes
Consideration of CO2 emission by fertilizer production
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Sources of N emission from soil(can there be too much ‘humus’)
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Regionalized OC contents in arable soils N surplus in agricultural soils
Thünen Report 64 (2018) UBA Texte 82/2003
≤ 30 kg Corg ha-1
30 - ≤ 50 kg Corg ha-1
50 - ≤ 70 kg Corg ha-1
70 - ≤ 90 kg Corg ha-1
< 90 kg Corg ha-1
Relation between OC contents and N emission?
>
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Körschens und Schulz (1999) UFZ-Bericht Nr. 13/1999
Optimum contents of organic matter?
Ton plus Feinschluff [%]
0 5 10 15 20 25 30 35 40
Co
rg [
%]
0,0
0,5
1,0
1,5
2,0
2,5
3,0
Bereich Sandboden
Bereich LehmbodenLoam
SandLowerlimit
Upperlimit
Upperlimit
Lowerlimit
Estimation from long-term fieldexperiments from differentiationof „inert“ and metabolizable C
Frequency distribution of humus classes in soilsdeveloped from loess under different land use
Düwel et al. (2007) BGR-Bericht Tgb.-Nr. 10782/06
Many non-arable soils are well above the limit
Arable Forest Grassland
Clay plus fine silt (%)(Organic matter contents, %)
Humus classes according to German soil classification
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Wessolek et al. (2008) UBA-BerichtUFOPLAN 202 71264
N emission due to exceeding ‘upper limit’of soil organic matter?
Yields and N emission from soil of the long-term field experiment Lauterbach (Erzgebirge)
More long-term field experiments:
Coefficient of determination: N saldo vs. OC: 0,04-0,61Coefficient of determination: N saldo vs. N fertilization: 0,62-0,92
Relation to OC indirect / no indication for upper limit
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Relation between N fertilization and N emission from Chinese paddy soils (n=107)
Chen et al. (2014) Nature
Relation between N fertilization and N emission
NH3 emission N2O emission N leaching
Direct relation between N fertilization and N emission(similar at with wheat and maize)
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N and soil management by catch crops
2 month after seeding (27/10)
6 weeks after seeding (27/09)
Mustard Fallow Clover Bristleoat
Phacelia TerraLife12 Spezies
Mix5 mustrad , clover
oat, phacelia
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Individual catch crops:Mustard, phacelia, bristle oat,clover, fallow (controll)
Exploration of larger soilvolume
Increase of biodiversity of soil organisms
Biodiverse catch crop mixtures:Mix4: 4 catch crop species
(3% legumes)
TerraLife: 12 catch crop species(23% legumes)
Differently diverse catch crops
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N uptake from different soil depths in monocultureand in diverse catch crop mixtures
Gentsch et al., unpublished
Niching ofplants
More effectiveresourceutilization
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Nmin stocks in autumn Nmin stocks in spring
Influence of catch crops on Nmin in soil
Gentsch et al., unpublished
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Nutrient release from mineralizationof catch crops in succeeding crop
TerraLife: + 20 kg N ha-1Gentsch et al., unpublished
N release from soil under maize
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N release from soil under maize
TerraLife: + 20 kg N ha-1
+ 27 kg K ha-1 + 2.5 kg P ha-1
K and P release from soil under maize
Gentsch et al., unpublshed
Diverse catch crop mixture is most effective
Nutrient release from mineralizationof catch crops in succeeding crop
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C fluxes between atmosphere and cultures
C fluxes
Leaf-to-stalk ratio:
Mustard: 0,79 ±0,03 TerraLife: 1.63±0,37
Gentsch et al., unpublished
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Bacterial diversity in soil under cornfollowing catch crops
Diversity of the active microbiome (RNA) in soil under maize following different catch crops
Aboveground diversity increases belowground diversity(Results cannot be shown, as they are not published yet)
Reinhold-Hurek et al., unpublished
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Dry weigh at humus degrading and accumulation rotations
Influence on maize yield
Rot.Humus
degradingRot.
Humus accumulating
1 Winter wheat 1 Winter wheat
2 Catch crop 2 Catch crop
3 Silage maize 3 Silage maize
1 Winter wheat 4 Winter wheat
2 Catch crop 5 Catch crop
3 Silage maize 6 Faver beans
Gentsch et al., unpublished
No significant differences, but experiment was performed at optimum N fertilization
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Final thoughts
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Final thoughts
• Loss of organic carbon due to conversion to arable land means also N loss Release of reactive N already during historical times
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Final thoughts
• Loss of organic carbon due to conversion to arable land means also N loss Release of reactive N already during historical times
• Microorganisms regulate C and N cycling by maintaining their stoichiometric C:N:P ratio(Cleveland und Lizpin, Catrufo, Kirkby, Manzoni, van Groenigen, Sinsabaugh, Richter, Spohn, Mooshammer, Zechmeister-Boltenstern …) C storage and N emission can be regulated by residue and fertilization management C storage and N emission can be regulated by catch crop management
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Final thoughts
• Loss of organic carbon due to conversion to arable land means also N loss Release of reactive N already during historical times
• Microorganisms regulate C and N cycling by maintaining their stoichiometric C:N:P ratio(Cleveland und Lizpin, Catrufo, Kirkby, Manzoni, van Groenigen, Sinsabaugh, Richter, Spohn, Mooshammer, Zechmeister-Boltenstern …) C storage and N emission can be regulated by residue and fertilization management C storage and N emission can be regulated by catch crop management
• Organic matter is not likely responsible for high N emissions
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Livestock unit per ha agricultural land N surplus in agricultural soils
UBA Texte 82/2003
It is rather mass husbandry
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Final thoughts
• Loss of organic carbon due to conversion to arable land means also N loss Release of reactive N already during historical times
• Microorganisms regulate C and N cycling by maintaining their stoichiometric C:N:P ratio(Cleveland und Lizpin, Catrufo, Kirkby, Manzoni, van Groenigen, Sinsabaugh, Richter, Spohn, Mooshammer, Zechmeister-Boltenstern …) C storage and N emission can be regulated by residue and fertilization management C storage and N emission can be regulated by catch crop management
• Organic matter is not likely responsible for high N emissions This is rather fertilization, particularly in areas with mass husbandry
CLIENT II
Final thoughts
• Loss of organic carbon due to conversion to arable land means also N loss Release of reactive N already during historical times
• Microorganisms regulate C and N cycling by maintaining their stoichiometric C:N:P ratio(Cleveland und Lizpin, Catrufo, Kirkby, Manzoni, van Groenigen, Sinsabaugh, Richter, Spohn, Mooshammer, Zechmeister-Boltenstern …) C storage and N emission can be regulated by residue and fertilization management C storage and N emission can be regulated by catch crop management
• Organic matter is not likely responsible for high N emissions This is rather fertilization, particularly in areas with mass husbandry
• Mineral fertilization can have also positive aspects N and also other nutrients are necessary for increasing soil OC stocks
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Loss of OCSouth Siberian and Kazakh steppe
Degraded agricultural soils(Chernozems, Kastanozems)
R² = 0.43P < 0.001
No fertilizationand bare fallow
→ Soil degradation
→ Loss of OC
→ Erosion
OC
(g
kg-1
)
Aggregate stability(Δ MWD)
Fertilization cancontribute to:
→ Higher NPP
→ Higher yield
→ Larger return ofcrop residues
→ Better aggregatestability
→ Less erosion
→ Larger OC storage
→ Better soil quality
Bischoff et al. (2016) AGEE
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• Loss of organic carbon due to conversion to arable land means also N loss Release of reactive N already during historical times
• Microorganisms regulate C and N cycling by maintaining their stoichiometric C:N:P ratio(Cleveland und Lizpin, Catrufo, Kirkby, Manzoni, van Groenigen, Sinsabaugh, Richter, Spohn, Mooshammer, Zechmeister-Boltenstern, …) C storage and N emission can be regulated by residue and fertilization management C storage and N emission can be regulated by catch crop management
• Organic matter is not likely responsible for high N emissions This is rather fertilization, particularly in areas with mass husbandry
• Mineral fertilization can have also positive aspects N and also other nutrients are necessary for increasing soil OC stocks Degraded soils show particular potential
Final thoughts
CLIENT IIDEU
Thank you very muchfor you attention
