Transcript Influence of tillage on SOC dynamics : C sequestration

Soil structure and C sequestration
under no tillage management
Gayoung Yoo* and Michelle M. Wander
Department of Natural Resources and
Environmental Sciences
University of Illinois
Variable no tillage influences
by 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.
Background
Wander et al., 1998
Total C (g C m-2)
10000
No till
NT
CT
Conventional
8000
6000
a
a
till
b
c
4000
2000
0
Monmouth
DeKalb
INPUT
OUTPUT
SOC
Soil erosion
Crop yield
microbes
Soil temp.
Soil CO2 efflux
Soil water
SOIL
STRUCTURE
Tillage
Soil structure and SOM dynamic models
Management
Soils
Climate
Century model
SOM
Submodel
Water
Balance
Submodel
Plant
Growth
Submodel
Residues
CO2
CO2
CO2
CO2
f (sand)
Topography
Slow
SOM
Active
SOM
Passive
SOM
CO2
f (clay)
Site description
DeKalb
Poorly
drained
Randomized complete block design
Drummer silty
- 3 blocks
clay loam
- Fixed effect: site, till
Monmouth
- Random effect: year, date
Somewhat
poorly drained
Muscatine silt
loam
Treatments
NT : no tillage
CT : conventional tillage
Objectives

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 methods

Soil CO2 efflux measurement
– Li Cor 6400 (from 2000 to 2002)

Environmental variables
– Soil temperature, soil moisture, penetration
resistance (PR), bulk density, and pore size
distribution

Statistical method
– ANOVA using PROC MIXED
– Non-linear regression using PROC NLIN (SAS
Institute)
10
b
8
a
a
a
6
4
2
0
NT
DeKalb
CT
NT
Specific SOC mineralization rate
(mCO2 s-1 / mg SOC )
CO2 evolution rate (umol m-2 s-1)
Seasonal mean and specific C
mineralization
8
c
6
b
4
a
a
2
0
CT
NT
Monmouth
CT
DeKalb
NT
CT
Monmouth
Soil physical parameters
Effect
Soil temp.
Soil water
-----oC------- -----%-----
Site
Tillage
† Means,
Bulk
density
Penetration
resistance
---g cm-3---
-- blows m-1--
DeKalb
18.85a
25.03b
1.32a
91.57b
Monmouth
18.24a
22.86a
1.39b
58.83a
NT
18.54a
24.30a
1.41b
70.47 b
CT
18.55a
23.6a
1.31a
59.97a
estimated with least square means, within site or tillage not followed by the same letter were
significantly different at P < 0.05.
Correlation coefficients
Soil temp
Soil water
PR
BD
Specific
C min
rates
Soil
temp
Soil
water
PR
BD
Specific
C min
rates
1
0.03
-0.01
0.31
0.27***
1
-0.19*
-0.30*
-0.34***
1
0.30 1
-0.06
-0.16
1
Development of Q10 equation

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
0.67
DeKalb
2.93 7.29
Monmouth
R2
(validation)
-0.18
0.63
0.31
Pore size distribution
Total pore
Macropore
Micropore
(> 30 um)
( < 30 um)
-------------------- ml g-1 soil --------------------DeKalb
NT
0.444 a
0.104 a
A
0.334 a
A
A
CT
0.442 a
0.109 a
0.340 a
Monmouth NT
0.339 a
0.068 a
0.271 a
CT
† Least
0.379 b
B
0.086 b
B
B
0.294 a
square means within site not followed by the same letter were significantly different at P < 0.05.
Nissen et al. (unpublished data)
Least limiting water range
Volumetric water content (cm3 cm-3)
(da Silva et al., 1994; Topp et al., 1994)
0.5
θfc Field capacity at -0.01 Mpa
(Haise et al., 1955)
θsr Soil resistance of 2 Mpa
LLWR
(Taylor et al., 1966)
0.1
0.5
θafp Air-filled porosity of 10 %
(Grable and Siemer, 1968)
θwp Wilting point at -1.5 Mpa
0.2
(Richards and Weaver, 1944)
1.1
1.5
Bulk density (g
cm-3)
The calculation of LLWR:
Pedotransfer functions (da Silva and Kay, 1997)
Limits
θfc
Functions
ln    4.15  0.69ln CLAY  0.40ln SOC  0.27ln Db
 ( 0.55 0.11 ln CLAY  0.02 ln SOC  0.10 ln Db ) ln
wet
θafp
θwp
dry
θsr
(1-Db/2.65) – 0.1
ln    4.15  0.69 ln CLAY  0.40 ln SOC  0.27 ln Db
 ( 0.55  0.11 ln CLAY  0.02 ln SOC  0.10 ln Db ) ln
ln SR   3.67  0.14 CLAY  0.77 SOC  (  0.48  0.12 CLAY  0.21 SOC ) ln 
 ( 3.85  0.10 CLAY ) ln Db
Data input
SOC, clay,
bulk density
bulk density
SOC, clay,
bulk density
SOC, clay,
bulk density
Mean LLWRs
Wet limit
Site
Till
θfc
θafp
Dry limit
θwp
θsr
LLWR
------------------------ cm3 cm-3 ------------------------------NT 0.541 c 0.379 b
0.347 c
0.346 c
0.032 a
CT 0.560 d 0.412 a
0.353 c
0.322 b
0.059 a
NT 0.427 b 0.360 a
0.212 b
0.276 b
0.083 b
0.196 a
0.243 a
0.141 c
DeKalb
Monmouth
CT
0.411 a 0.384 a
0.010
0.008
0.006
0.004
0.002
Specific SOC min rate (g CO2 s-1 / g SOC)
Specific SOC min rate (mg CO2 s-1 / mg SOC)
LLWR and SOC mineralization
0.010
Pearson correlation coefficient
Pearson cor coefficient = 0.650
= 0.59921
(p=0.0025)
(p=0.0008)
0.008
0.006
0.004
0.002
0.000
Col 1 vs Col 2
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
LLWR (cm cm-3)
0.000
0.00
0.05
0.10
0.15
LLWR (cm cm-3)
0.20
0.25
Summary 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
structure

Intermediate protective capacity soils
– Medium clay content, medium SOC, medium
macroporosity, high BD and LLWR
– Physical properties can be altered to affect biological
activity and C sequestration by tillage practice
Acknowledgement

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.