Division of Applied Life Science Gyeongsang National University Shortterm preaerobic digestion of biomass amended soil strongly decreased net global warming potential during rice cultivation ID: 935607
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Slide1
Hyeon Ji SongSoil science lab.
Division of Applied Life Science
Gyeongsang National University
Short-term pre-aerobic digestion
of biomass amended soil
strongly
decreased net global warming potential
during
rice
cultivation
Slide2Mitigate global warming : Carbon sequestration
Importance of
soil organic carbon (SOC) stock
Research background
Improve soil quality
Physical properties
Improve
soil aggregates
Ameliorate air and water permeability
Increase water holding capacity
Chemical properties
Enhance
nutrient holding capacityImprove pH buffering capacityImmobilize pollutants
Biological propertiesBoost microbial activityEnhance microbial diversity
Atmosphere
(589
PgC
/y)
Vegetation
(450-650
PgC)
Photosynthesis(C uptake)
Humification
(C
Storage)
Decomposition(C emission)
Soil organic C pool(1500-2400 PgC)
Slide3Temperate
mono-cropping system
Winter fallow season
Cash
crop cultivation season
Biomass
cultivation
: Cover cropping
Biomass recycling
: Green manure (GM)
1.
Limit soil erosion : Improve soil physical properties by root activity (mulching effect)
2. Promote SOC protecting potential in soil aggregates : Enhance soil microbial community by diversified
cropping systems
1. Increase carbon input
: Non-leguminous green manure
(barley,
wheat, rye) - High biomass productivity - High C:N ratio
2. Substitute
for chemical fertilizer
: Leguminous green manure (Hairy vetch, alfalfa, milk vetch) - Nitrogen fixing capacity - Low C:N ratio
Research background
Recommended
practices
C sequestration
potential
(Mg C ha
-1
yr
-1
) Conservation tillage0.10-1.00 Winter cover crop 0.05-0.25 Manuring0.05-0.15 Diverse cropping systems0.05-0.25 Mixed farming0.10-0.20 Water management 0.10-0.20 Erosion control0.15-0.30 Salinity control0.06-0.20
(Lal et al., 2004)
Soil managements to increase SOC stock : Winter cover cropping
Slide4Research background
Green manure (Biomass)SOM
Aerobic
(+O
2
)
respiration
Heterotrophs
CO
2
CO2
SOM digestion dynamicsNegative aspects of green manure in rice paddy
Slide5Research background
Negative aspects of green manure in rice paddy
SOM digestion dynamics
SOM
(
mainly
acetate)
CO
2
CO
2
Methanotrophs
(>-200mV)(surface aerobic layer and rhizosphere)Methanogens(-200mV)Anaerobic (-O
2) respirationCH4Greenhouse gas
GWP*
Sources
Carbon
dioxide
(
CO
2)
1
Energy use, industry
Agriculture = C sink
Methane
(CH
4)
25
Natural gas, Landfill, Wetland
Agriculture
(rice paddy soil)
CH4IPCC (2007)Green manure (Biomass)
Slide6Green manure
(CH
2
O)
n
Flooded soil
condition
Dried soil condition
Aerobic
microbial respiration
Aerobic decomposition
Labile SOM
: Stabilization of organic matters from biomass in aerobic condition soil before floodingResearch background
Short-term pre-aerobic digestion of green manure-Sugars-Cellulose-ProteinsCO
2
-
Fulvic
acids
-
Humic
acids
-
Humin
Relative Resistant SOM
Slide7Green manure
(CH
2
O)
n
Flooded soil
condition
Dried soil condition
Aerobic
microbial respiration
CO
2
Research backgroundShort-term pre-aerobic digestion of green manure-Sugars
-Cellulose-Proteins-Fulvic acids-Humic acids-Humin
CH4
Anaerobic decomposition
Anaerobic
microbial respiration (-200mV)
: Stabilization
of
organic matters from biomass in aerobic condition soil before flooding
Aerobic decomposition
Labile SOM
Relative Resistant SOM
Slide8Objectives
In order
to evaluate the feasibility of
short-term pre-digestion of biomass
before irrigation on decreasing global warming impact
during rice cultivation,
1.
CH
4
emission
and
N2O emission were monitored for evaluating global warming potential (GWP).2. Soil organic carbon (SOC) stock change was estimated using net ecosystem carbon budget (NECB) analysis 3.
Net GWP was compared among treatments which have different biomass incorporating time.
Slide9Materials & Methods
Experimental plot installation
Soil
texture
pH
(1:5 H
2
O)
Organic matter
(g/kg)
Total N
(g/kg)
Av. P2
O5(mg/kg)Exchangeable cation (cmol+/kg)
Soil
series
K
Ca
Mg
Na
Clay Loam
6.2
20.9
1.3
98
0.27
5.12
0.50
0.08
Pyeongtaek
Soil characteristics before
experimentBiomass productivity and chemical properties of cover crops ParametersMixtureBarleyHairy vetch Total or MeanBiomass (Mg
ha-1, DW)3.11.2
4.3
Total carbon
(g kg
-1
)
505
499
502
Total nitrogen
(g kg
-1
)
10.1
39.3
24.7
C:N ratio
50.5
12.7
31.6
Slide10Materials & Methods
Treatments
0day
Green manure application
-10days
-30days
-20days
Short-term pre-aerobic decomposition
Anaerobic decomposition (rice cultivation)
7days
Green manure
application
Green manure
application
Green manure
application
Irrigation
Harvesting
Transplanting
Cover crops
harvesting
(Early June)
(Late October)
Slide11Materials & Methods
=
Net GWP
(Mg CO
2
equiv. ha
-1
)
(
CH
4
flux 25)
(N2O flux 298) +
(∆ SOC stock) -Net global warming potentials
Slide12=
Net GWP
(Mg CO
2
equiv. ha
-1
)
(
CH
4
flux
25) (N
2O flux 298) +(∆ SOC stock
) -Materials & Methods1. GHGs sampling Method : Closed chamber method using transparent acrylic chamber
Time : Once
a week for 30minutes (10:30 – 11:00 AM)
Target gas :
CO
2 and N2O
Gas chromatography
(GC, SHIMADZU GC-2010)GHGs emission measurement
2. GHG emission rate & seasonal fluxGHG emission rate=
ρ
x
VA
xΔcΔ
tx
273T
(mg m
-2
hr
-1)Seasonal GHG flux= (kg ha-1)ΡGas density (g m-3)VVolume of chamber (m3)ASurface area of chamber (m2)Δc/Δt
Rate of gas concentration in the chamber (mg m-3 hr-1)T
Absolute
temperature of
chamber
(K)
Rate of gas flux per day
in
i
th
sampling
interval
(g
m
-2
day
-1
)
The number of days in the
i
th
sampling
interval (day)
Ρ
Gas
density (g m
-3
)
V
Volume
of
chamber
(m
3
)
A
Surface
area of
chamber
(m
2
)
Δ
c/
Δ
t
Rate of gas concentration in the
chamber (mg m
-3
hr
-1
)
T
Absolute
temperature of
chamber
(K)
Rate of gas flux per day
in
i
th
sampling
interval
(g
m
-2
day
-1
)
The number of days in the
i
th
sampling
interval (day)
Slide13Materials & Methods
Net Ecosystem Carbon Budget analysis : SOC stock change analysis
=
Net GWP
(Mg CO
2
equiv. ha
-1
)
(
CH
4 flux 25
) (N2O flux 298)
+(NECB 44/12) -
Carbon input
Carbon output
Ecosystem
∆
Carbon stock
=
∑
C input - ∑
C output
Slide14Materials & Methods
NECB
=
NPP
R
h
(CO
2
)
-
Manure
+
Harvest-Σ C InputΣ C Output -
=CH4-Manure
aboveground
Rhizodeposit
Litter
CO
2
CH
4
Harvest
C output
C input
NPP : Net primary production
R
h
: Heterotrophic respiration
Root
NPP
Net Ecosystem Carbon Budget analysis : SOC
stock change
analysis
Slide15Materials & Methods
Input
NPP
Grain & Straw
Biomass × TOC (%)
Root
10% of aboveground biomass
Litter
5% of above & root biomass
Rhizodeposit
15% of total biomass
Green manure
Aboveground
Biomass × TOC (%)
Output
Mineralized
C loss
Σ
CO
2
loss
Closed chamber method
Σ
CH
4
loss
Harvest removal
Harvest
Grain & Straw Biomass × TOC (%)
1. Parameter analysis
2. Mineralized C loss estimation
Method : Closed chamber method using opaque chamberTime : Once a week for 30minutes (10:30 – 11:00 AM)
Analysis : Gas chromatography (GC, SHIMADZU GC-2010)Target gas : CO2 and CH4
Opaque round chamber
without plant
0.3m
Net Ecosystem Carbon Budget analysis : SOC
stock change
analysis
Slide16Results
Greenhouse gases emission &
fluxes – CH
4
b
b
b
a
Biomass application
67%
60%
78%
Slide17Results
Greenhouse gases emission & fluxes –
N2
O
Biomass application
Slide18Results
Day before irrigation
Net primary productivity
(NPP, kg
C ha
-1
)
Grain
Straw
Root
LitterRhizodeposit
Total303180
2400
558
307
967
7412
20
3190
2444
563
310
976
7483
10
3205
2439
564
310
978749603414257859933010387959NECB = (NPP + Green manure) – (Harvest + Mineralized C)
Slide19Results
b
b
b
a
81%
71%
90%
NECB = (NPP + Green manure) – (Harvest +
Mineralized C
)
Slide20Results
NECB = (NPP + Green manure) – (Harvest + Mineralized C)
Slide21Results
Net GWP = GWP – SOC stock change
99%
68%
93%
b
b
b
a
Slide22Pre-aerobic digestion at least 10days
diminished greenhouse gas emission impacts of cover crop biomass application without soil organic carbon stock depletion
in rice paddy soil.22
Short-term pre-aerobic digestion
reduced
CH
4
emission
56-78% over no aerobic digestion while
N2O emission was negligibly affected. Short-term pre-aerobic digestion did not affect SOC stock accumulation via biomass application.
Due to strong reduction of CH4 emission, short-term pre-aerobic decomposition highly decreased net GWP by 68-99%, compared with no aerobic decomposition.Conclusions