Soil structure and C sequestration Soil structure and C sequestration under no tillage managementunder no tillage management
Gayoung Yoo* and Michelle M. WanderGayoung Yoo* and Michelle M. Wander
Department of Natural Resources and EnDepartment of Natural Resources and Environmental Sciencesvironmental Sciences
University of IllinoisUniversity of Illinois
Variable no tillage influences Variable no tillage influences by sitesby sites
No tillage (NT) does not always increase C sequestration.
– Soils are fine textured and poorly drained where soil erosion is not a major factor or yield under NT is reduced.
BackgroundBackground
Monmouth DeKalb
Tot
al C
(g
C m
-2)
0
2000
4000
6000
8000
10000NTCT
a a
bc
Wander et al., 1998
No till
Conventional till
SOIL STRUCTURE
INPUT
Crop yield
Soil CO2 efflux
OUTPUT
Soil erosion
microbes
SOC
Soil waterSoil temp.
Tillage
Soil structure and SOM dynamic modelsSoil structure and SOM dynamic models
WaterBalance
Submodel
ActiveSOM
SlowSOM
PassiveSOM
Residues
PlantGrowth
Submodel
CO2
CO2
CO2
CO2
CO2
SOMSubmodel
Climate Soils TopographyManagement
Century model
f (sand)
f (clay)
Site description Site description DeKalb
Poorly drained
Drummer silty clay loam
Monmouth
Somewhat poorly drained
Muscatine silt loam
Treatments
NT : no tillage
CT : conventional tillage
Randomized complete block design
- 3 blocks
- Fixed effect: site, till
- Random effect: year, date
ObjectivesObjectives
Investigate soil CO2 evolution patterns where tillage practices have had varied influences on SOC
Characterize site- and treatment-based differences in soil physical factors that might control C dynamics
Determine whether the soil structural quality explains differences in SOC mineralization
Experimental methodsExperimental methods Soil CO2 efflux measurement
– Li Cor 6400 (from 2000 to 2002)
Environmental variables – Soil temperature, soil moisture, penetration resistanc
e (PR), bulk density, and pore size distribution
Statistical method– ANOVA using PROC MIXED– Non-linear regression using PROC NLIN (SAS Institu
te)
Seasonal mean and specific C Seasonal mean and specific C mineralization mineralization
CO
2 ev
olut
ion
rate
(um
ol m
-2 s
-1)
0
2
4
6
8
10
NT NT CTCT
DeKalb Monmouth
aaa
b
Spec
ific
SOC
min
eral
izat
ion
rate
(m
CO
2 s-
1 / m
g SO
C )
0
2
4
6
8
NT NT CTCT
a
c
b
a
DeKalb Monmouth
Soil physical parametersSoil physical parameters
Soil water
-----%-----
25.03b
22.86a
24.30a
23.6a
Bulk density
---g cm-3---
1.32a
1.39b
1.41b
1.31a
† Means, estimated with least square means, within site or tillage not followed by the same letter were significantly different at P < 0.05.
EffectSoil temp.
-----oC-------
Site DeKalb 18.85a
Monmouth 18.24a
Tillage NT 18.54a
CT 18.55a
Penetration
resistance
-- blows m-1--
91.57b
58.83a
70.47 b
59.97a
Correlation coefficientsCorrelation coefficients
Soil temp
Soil water
PR BDSpecific
C min rates
Soil temp 1 0.03 -0.01 0.31 0.27***
Soil water 1 -0.19* -0.30* -0.34***
PR 1 0.30 - -0.06
BD 1 -0.16
Specific
C min rates
1
Development of QDevelopment of Q10 10 equationequation Basic Q10 model with soil temperature and gravimetric
water contents– Soil CO2 evolution = (b + r*SWC)*Q10 (Ts-10)/10
Site Q10 b r R2
DeKalb2.93 7.29 -0.18 0.63
Monmouth
R2
(validation)
0.67
0.31
Pore size distributionPore size distribution
† Least square means within site not followed by the same letter were significantly different at P < 0.05. Nissen et al. (unpublished data)
Total pore Macropore
(> 30 um)
Micropore
( < 30 um)
-------------------- ml g-1 soil ---------------------
DeKalb NT 0.444 a 0.104 a 0.334 a
CT 0.442 a 0.109 a 0.340 a
Monmouth NT 0.339 a 0.068 a 0.271 a
CT 0.379 b 0.086 b 0.294 a
A
B
A
B
A
B
Least limiting water rangeLeast limiting water range(da Silva et al., 1994; Topp et al., 1994)(da Silva et al., 1994; Topp et al., 1994)
θfc Field capacity at -0.01 Mpa(Haise et al., 1955)
θafp Air-filled porosity of 10 % (Gra
ble and Siemer, 1968)
θsr Soil resistance of 2 Mpa (Taylor et al., 1966)
θwp Wilting point at -1.5 Mpa (Ri
chards and Weaver, 1944)
Bulk density (g cm-3)1.1 1.5V
olum
etri
c w
ater
con
tent
(cm
3 cm
-3)
0.2
0.5
LLWR0.1 0.5
The calculation of LLWR: The calculation of LLWR: Pedotransfer functions Pedotransfer functions (da Silva and Kay, 1997)(da Silva and Kay, 1997)
Limits Functions Data input
θfcSOC, clay,
bulk density
θafp bulk density
θwpSOC, clay,
bulk density
θsrSOC, clay,
bulk density
ln)ln10.0ln02.0ln11.055.0(
ln27.0ln40.0ln69.015.4ln
b
b
DSOCCLAY
DSOCCLAY
ln)ln10.0ln02.0ln11.055.0(
ln27.0ln40.0ln69.015.4ln
b
b
DSOCCLAY
DSOCCLAY
bDCLAY
SOCCLAYSOCCLAYSR
ln)10.085.3(
ln)21.012.048.0(77.014.067.3ln
wet
dry
(1-Db/2.65) – 0.1
Mean LLWRsMean LLWRs
Site Till θfc θafp
------------------------ cm3 cm-3 -------------------------------
DeKalbNT 0.541 c 0.379 b
CT 0.560 d 0.412 a
MonmouthNT 0.427 b 0.360 a
CT 0.411 a 0.384 a
Wet limit Dry limit
θwp θsr
0.347 c 0.346 c
0.353 c 0.322 b
0.212 b 0.276 b
0.196 a 0.243 a
LLWR
0.032 a
0.059 a
0.083 b
0.141 c
LLWR and SOC mineralizationLLWR and SOC mineralization
Col 1 vs Col 2
LLWR (cm cm-3)
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
Spec
ific
SO
C m
in r
ate
( g
CO
2 s-1
/ g
SO
C)
0.000
0.002
0.004
0.006
0.008
0.010
Pearson cor coefficient = 0.650 (p=0.0008)
LLWR (cm cm-3)
0.00 0.05 0.10 0.15 0.20 0.25Spe
cific
SO
C m
in r
ate
(mg
CO
2 s
-1 /
mg
SO
C)
0.000
0.002
0.004
0.006
0.008
0.010
Pearson correlation coefficient= 0.59921 (p=0.0025)
Summary and ConclusionsSummary and Conclusions
Inherently high protective capacity soils– High clay content, high SOC, high macroporosity, low
BD, low LLWR– Not likely to be affected much by practices that alter st
ructure
Intermediate protective capacity soils– Medium clay content, medium SOC, medium macropo
rosity, high BD and LLWR– Physical properties can be altered to affect biological a
ctivity and C sequestration by tillage practice
AcknowledgementAcknowledgement
I would also like to thank Todd Nissen, Verónica Rodríquez, Inigo Virto, and Iosu Garcia for their invaluable assistance in the field.
Special thanks to Emily Marriott, Ariane Peralta, and Carmen Ugarte for their helpful discussion, editing, and advice.
