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Soil structure and C sequestration under no tillage management Gayoung Yoo* and Michelle M. Wander Department of Natural Resources and Environmental Sciences.

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Presentation on theme: "Soil structure and C sequestration under no tillage management Gayoung Yoo* and Michelle M. Wander Department of Natural Resources and Environmental Sciences."— Presentation transcript:

1 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

2 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.

3 Background Wander et al., 1998 No till Conventional till

4 SOIL STRUCTURE INPUT Crop yield Soil CO 2 efflux OUTPUT Soil erosion microbes SOC Soil water Soil temp. Tillage

5 Soil structure and SOM dynamic models

6 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

7 Objectives Investigate soil CO 2 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

8 Experimental methods Soil CO 2 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)

9 Seasonal mean and specific C mineralization

10 Soil physical parameters Soil water -----% b 22.86a 24.30a 23.6a Bulk density ---g cm a 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 < Effect Soil temp o C SiteDeKalb18.85a Monmouth18.24a TillageNT18.54a CT18.55a Penetration resistance -- blows m b 58.83a b 59.97a

11 Correlation coefficients Soil temp Soil water PRBD Specific C min rates Soil temp *** Soil water1-0.19*-0.30*-0.34*** PR BD Specific C min rates 1

12 Development of Q 10 equation Basic Q10 model with soil temperature and gravimetric water contents – Soil CO 2 evolution = (b + r*SWC)*Q10 (Ts-10)/10 SiteQ 10 brR2R2 DeKalb Monmouth R 2 (validation)

13 Pore size distribution † Least square means within site not followed by the same letter were significantly different at P < Nissen et al. (unpublished data) Total poreMacropore (> 30 um) Micropore ( < 30 um) ml g -1 soil DeKalbNT0.444 a0.104 a0.334 a CT0.442 a0.109 a0.340 a MonmouthNT0.339 a0.068 a0.271 a CT0.379 b b0.294 a A B A B A B

14 Least limiting water range (da Silva et al., 1994; Topp et al., 1994) θ fc Field capacity at Mpa (Haise et al., 1955) θ afp Air-filled porosity of 10 % (Grable and Siemer, 1968) θ sr Soil resistance of 2 Mpa (Taylor et al., 1966) θ wp Wilting point at -1.5 Mpa (Richards and Weaver, 1944) Bulk density (g cm -3 ) Volumetric water content (cm 3 cm -3 ) LLWR

15 The calculation of LLWR: Pedotransfer functions (da Silva and Kay, 1997) LimitsFunctionsData input θ fc SOC, clay, bulk density θ afp bulk density θ wp SOC, clay, bulk density θ sr SOC, clay, bulk density wet dry (1-D b /2.65) – 0.1

16 Mean LLWRs SiteTillθ fc θ afp cm 3 cm DeKalb NT0.541 c0.379 b CT0.560 d0.412 a Monmouth NT0.427 b0.360 a CT0.411 a0.384 a Wet limit Dry limit θ wp θ sr c0.346 c c0.322 b b0.276 b a0.243 a LLWR a a b c

17 LLWR and SOC mineralization

18 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

19 Acknowledgement I would also like to thank Todd Nissen, Ver ó nica Rodr í quez, 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.


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