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Soil resistance and resilience to compaction as affected by the clay-organic carbon relation

Emmanuel Arthur Per Moldrup Per Schj ønning Lis W. de Jonge. Soil resistance and resilience to compaction as affected by the clay-organic carbon relation. ASA , CSSA, and SSSA  International Annual Meetings Oct 16-19, 2011 San Antonio, TX. Introduction.

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Soil resistance and resilience to compaction as affected by the clay-organic carbon relation

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  1. Emmanuel Arthur Per Moldrup Per Schjønning Lis W. de Jonge Soil resistance and resilience to compaction as affected by the clay-organic carbon relation ASA, CSSA, and SSSA International Annual Meetings Oct 16-19, 2011San Antonio, TX

  2. Introduction • Anthropogenic stresses imposed on soils challenge their ability to function • Soil stability is characterized by its resistance and resilience to imposed stress • Compaction by agricultural machinery increases bulk density and reduces pore functions ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  3. Introduction • Soils resistance and resilience to compaction is driven by several factors (water content, texture, clay type, organic matter etc.) Hypothesis • The main driver governing resilience in soils is the level of clay saturation by organic carbon ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  4. Introduction Objective • Assess the role of clay saturation by organic carbon in soil resilience to compaction using three functional indicators ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  5. Methodology • Functional indicators: • Void ratio, e • Air permeability, ka • Air filled porosity, ε ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  6. Methodology • Soils – 3 sandy loams: ~17 % clay Different long term management = different organic carbon contents: MFC = Mixed forage cropping MCC = Mixed cash cropping CCC = Cereal cash cropping 10g clay ≈ 1g OC (Dexter et al., 2008) 1:10 line ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  7. Methodology • Compaction test Freeze-thaw cycles [FT] -10°C & -100 hPa Compaction (200kPa) @2mm/min 100 cm3 7 days -100 hPa drained to -100 hPa (Void ratio, e; air permeability, ka Air filled porosity, ε) Rebound recovery [RR] (ka, ε, e) ka, ε, e Wet-dry cycles [WD] saturation & 40°C Resistance (RST) ka, ε, e ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  8. Methodology • Quantification of resistance and resilience • Compression index, Cc, from Gompertzmodel σ = applied stress e = void ratio a, b, c = model parameters Low Cc = high resistance to compaction ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  9. Methodology • Quantification of resistance and resilience • Compression index, Cc, from Gompertzmodel • Absolute values (e, ka, ε) • Indexed values: Resistance [RST] = Original value – Value after compaction Original value Resilience [PR] = Original value – Recovery value Original value Range : 0 – 1 0 = maximum resistance/resilience 1 = no resistance/resilience ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  10. Results • Functional indicators prior to compaction (-100hPa) ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  11. Results • Functional indicators prior to compaction (-100hPa) ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  12. Results • Compaction resistance (Cc) ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  13. Results • Compaction resistance (Cc) • Higher clay saturation = higher compression resistance • Increasing initial void ratio has relatively less impact on Cc for MFC ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  14. Results • Resistance (RST) and resilience (PR) • Air permeability Absolute values Indexed values ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  15. Results • Resistance (RST) and resilience (PR) • Void ratio Absolute values Indexed values ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  16. Results • Resistance (RST) and resilience (PR) • Air-filled porosity Absolute values Indexed values ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  17. Results • Relation between resistance and resilience (void ratio) ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  18. Conclusions • For differently managed soils, the clay-organic carbon relation governs structural stability • Increased saturation of clay by organic matter: • increased compaction resistance usingεand e as indicators • reduced the effect of initial void ratio on compression resistance • Increased soil resilience after natural recovery, wet-dry and freeze-thaw cycles ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  19. Acknowledgements • Project Soil Infrastructure, Interfaces, and Translocation Processes in Inner Space (Soil-it-is) • Funding Danish Research Council for Technology and Production Sciences • STAiR ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

  20. ASA, CSSA, and SSSA International Annual Meetings. Oct 16-19. San Antonio, TX

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