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Soil C Dynamics Following Addition of 13 C-labeled Grain Sorghum ( Sorghum bicolor ) Residue. Paul White and Dr. Charles W. Rice Department of Agronomy Kansas State University Manhattan, KS. Carbon Sequestration. Atmospheric CO 2 levels have increased from 260 to 370 ppmv (IPPC, 2004). - PowerPoint PPT Presentation
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Soil C Dynamics Following Addition of 13C-labeled
Grain Sorghum (Sorghum bicolor) Residue
Paul White and Dr. Charles W. RiceDepartment of Agronomy
Kansas State University
Manhattan, KS
Carbon SequestrationCarbon Sequestration
• Atmospheric CO2 levels have increased from 260 to 370 ppmv (IPPC, 2004).
• Increasing soil C storage may assist in offsetting increases in CO2 due to fossil fuel emissions until cleaner fuel technology is available on a large scale.
• Understanding dynamics of C flow in differently managed ecosystems will be important to forecast C-sequestration effectiveness and extent.
• Possible manipulation of ecosystem to increase soil C storage potential
Soil Belowground Soil Belowground BiologyBiology
COCO22
SunlightSunlight
TemperatureTemperature
MoistureMoisture
NutrientsNutrients
Substrate Substrate QualityQuality
InputsInputs
OutputsOutputs
Adapted from Paul and Clark, 1996
Readilydecomposable
Moderatelydecomposable
ResistantPlant residue
CO2
CO2 CO2
Slow soil CStable soil C
CO2
CO2
Microbial Biomass C
Plant and microbialbyproducts
CO2
INPUTSINPUTS
= OUTPUTS= OUTPUTS
Temporal C Temporal C changes in soil changes in soil aggregates?aggregates?
Changes in microbial community Changes in microbial community dynamics?dynamics?
ObjectivesObjectives
During one growing season:
• Measure the mineralization of 13C-labeled plant residue
• Measure the changes in soil TC and TN• Measure the changes in soil TC and 13C in macro-
and microaggregates• Determine microbial community changes in
response to added residue
Materials and MethodsMaterials and Methods
Ashland Experimental Farm, Manhattan, KS
• Continuous Sorghum under No-Continuous Sorghum under No-Tillage (NT) and Conventional Tillage (NT) and Conventional Tillage (CT)Tillage (CT)
• 4 Blocks4 Blocks
• 2 Residue Levels: Control (no 2 Residue Levels: Control (no residue) and 0.5% by weightresidue) and 0.5% by weight
• 7 Sample Times: 0, 3, 16, 25, 40, 7 Sample Times: 0, 3, 16, 25, 40, 68, and 159 d68, and 159 d
• Data analyzed using SAS v9 Proc Data analyzed using SAS v9 Proc Mixed and means separated at the Mixed and means separated at the 5% significance level (SAS Institute, 5% significance level (SAS Institute, Cary N.C).Cary N.C).
Field Microcosm ExperimentField Microcosm Experiment
Materials and MethodsMaterials and Methods
0.5X Hoagland’s Pulse labeled 5X with 100% 13CO2
Pre-boot stage (about 65 d)
Above ground material removed, freeze dried, shredded, and the 4 to 6 mm fraction retained for field experiment
Aboveground Residue Characteristics
Total C 13C (PDB)
----%---- -----‰-----
42 570
Sorghum bicolorSorghum bicolor CV: Mycogen 1506 CV: Mycogen 1506
Anion and Cation Exchange Resin bag
NT 2.1 g 13C labeled residue placed on soil surface
CT 2.1 g
Mixed evenly with upper 15 cm soil with soil
15 cm15 cm
20 cm deep by 20 cm deep by 5 cm diameter 5 cm diameter PVC coresPVC cores
Materials and MethodsMaterials and Methods
Materials and MethodsMaterials and Methods
0 cm
5 cm
15 cm
Anion and Cation Exchange Resin bag
Soil separated into 0-5 and 5-15 Soil separated into 0-5 and 5-15 cm sections and sieved (4 mm) cm sections and sieved (4 mm) and either air-dried, put in 4 and either air-dried, put in 4 °°C C cooler, or freeze dried depending cooler, or freeze dried depending on analysis.on analysis.
Sample Times:
0 3 16 25 40 68 159d0 3 16 25 40 68 159d
Total % C and N
13C Whole Soil
13C Aggregates (>1000 m, 250-1000 m, 53-250 m, and 20-53 m)
Phospholipid Fatty Acids
Neutral Lipid Fatty Acids
Temporal C Temporal C changes in changes in aggregates?aggregates?
Changes in microbial Changes in microbial community structure?community structure?
Overall system stabilityOverall system stability
New input decomposition New input decomposition and retentionand retention
C measurements C measurements on a scaled on a scaled approachapproach
Materials and MethodsMaterials and Methods
Total % soil C, N by dry combustion & TCD Total % soil C, N by dry combustion & TCD detectiondetection
1313C whole soil measured by conversion to COC whole soil measured by conversion to CO22
using dry combustion and isotopic using dry combustion and isotopic 1313C C measured using Europa 20-20 IRMS.measured using Europa 20-20 IRMS.
1313C Data reported relative to the Pee Dee C Data reported relative to the Pee Dee Belemnite (1.12372% Belemnite (1.12372% 1313C, or 0C, or 0‰‰))
Materials and MethodsMaterials and Methods
Soil Chemical and Physical Soil Chemical and Physical Parameters and 2004 Parameters and 2004
Climate DataClimate Data
Soil: Muir silt loamSoil: Muir silt loam
TillageTillage Depth Depth pHpH P P CaCa K K MgMg Na Na SOSO44-S-S NH NH44-N -N NONO33-N-N TC TC TNTN
1:11:1 -----------------------mg/kg------------------------ ---- -----------------------mg/kg------------------------ ----%----%----
CTCT 0-50-5 5.45.4 128 128 18441844 317 317 281281 3.6 3.6 7.57.5 3.6 3.6 8.28.2 1.2 1.2 0.110.11
CTCT 5-155-15 5.75.7 52 52 22092209 193 193 308308 6.0 6.0 7.67.6 2.8 2.8 3.43.4 1.2 1.2 0.110.11
NTNT 0-50-5 5.05.0 158 158 17681768 262 262 251251 3.7 3.7 8.38.3 2.9 2.9 5.45.4 1.9 1.9 0.170.17
NTNT 5-155-15 5.85.8 41 41 22012201 173 173 291291 5.8 5.8 6.56.5 2.5 2.5 2.42.4 1.4 1.4 0.130.13
Bulk Density: NT=1.40 g/cmBulk Density: NT=1.40 g/cm33 CT=1.36 g/cm CT=1.36 g/cm3 3 (G. Doyle, Ph.D. (G. Doyle, Ph.D. Dissertation)Dissertation)
Data reported on a Mg/ha to 15 cm depth basisData reported on a Mg/ha to 15 cm depth basis
2004 Precipitation2004 Precipitation
0
20
40
60
80
100
120
140
160
180
200
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Pre
cip
(mm
)
Sample Times:
2004 Temperature2004 Temperature
-10
-5
0
5
10
15
20
25
30
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Mea
n T
emp
(C
)
2004 Air Temperature2004 Air Temperature
1980-2003 Air Temp1980-2003 Air Temp
ResultsResults
Total Soil C Total Soil C –– Tillage X Depth InteractionTillage X Depth Interaction
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=0 Soil C
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=1 Soil C
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=2 Soil C
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=3 Soil C
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=4 Soil C
Treatment
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Time=5 Soil C
010
20304050
60
MgC/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=6 Soil C
aa aa aabb
aa aa aabb
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=1 Soil N
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
T=0 Soil N
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=2 Soil N
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=3 Soil N
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=4 Soil N
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=5 Soil N
0
1
2
3
4
5
MgN/ha
0-5 5-15 0-5 5-15
CT CT NT NT
Treatment
Time=6 Soil N
Total Soil N Total Soil N –– Tillage X Depth InteractionTillage X Depth Interaction
CT 0-5 CT 0-5 1313C remaining C remaining during experimentduring experiment
4.5
5
5.5
6
0 10 20 30 40 50 60 70 80
Time (d)
ln10
0+
13
C CT0-5block1
CT0-5block2
CT0-5block3
CT0-5block4
Kinetics modeled as Kinetics modeled as first order having a first order having a rapid and slow phase rapid and slow phase according to: according to:
CCtt=C=Coo-e-ektkt
CT 5-15 CT 5-15 1313C remaining C remaining during experimentduring experiment
4.5
5
5.5
6
0 10 20 30 40 50 60 70 80
time (d)
100+
ln13
C CT5-15block1
CT5-15block2
CT5-15block3
CT5-15block4
NT 0-5 NT 0-5 1313C remaining C remaining during experimentduring experiment
4.5
5
5.5
6
0 10 20 30 40 50 60 70 80
NT0-5block1
NT0-5block2
NT0-5block3
NT0-5block4
Residue Decomposition KineticsResidue Decomposition Kinetics
RapidRapid SlowSlow
---------k/day---------------------k/day------------
-0.0316-0.0316 -0.0024-0.0024
By T=5, no significant difference By T=5, no significant difference between tillage or depth in remaining between tillage or depth in remaining total amount of total amount of 1313C in soil:C in soil:
0-15 cm average 0-15 cm average 1313CC
----------------‰ (PDB)--------‰ (PDB)--------
CTCT +28.66+28.66
NTNT +34.63+34.63
ConclusionsConclusions
• Addition of 0.5% by weight grain sorghum residue did not have significant impacts on soil C and N dynamics during the growing season Indicating relative macro system stability
• Decomposition kinetics and residual 13C levels were not different between tillage regimes Label detectable throughout growing season
• 13C Aggregate analysis and microbial lipids analysis may indicate management effects at a finer resolution
AcknowledgmentsAcknowledgments• Geronimo Watson, Karina Fabrizzi, Jamey Geronimo Watson, Karina Fabrizzi, Jamey
Duesterhaus, and undergraduate lab techsDuesterhaus, and undergraduate lab techs• Dr. Chuck RiceDr. Chuck Rice• Dr. Mary-Beth KirkhamDr. Mary-Beth Kirkham• Dr. Clenton OwensbyDr. Clenton Owensby• Dr. Dallas PedersonDr. Dallas PedersonThis material is based upon work supported by the Cooperative State This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Research, Education, and Extension Service, U.S. Department of Agriculture, Under Agreement No. 2001-38700-11092.Agriculture, Under Agreement No. 2001-38700-11092.