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Soil Carbon and Agricultural Land Management in Semi-Arid Central Spain

Soil Carbon and Agricultural Land Management in Semi-Arid Central Spain. Darcy Boellstorff Assistant Professor, Bridgewater State College, Massachusetts. Economic and societal benefits Food source stability Biodiversity Soil carbon and soil restoration determined by site-specific processes

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Soil Carbon and Agricultural Land Management in Semi-Arid Central Spain

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  1. Soil Carbon and Agricultural Land Management in Semi-Arid Central Spain Darcy Boellstorff Assistant Professor, Bridgewater State College, Massachusetts

  2. Economic and societal benefits Food source stability Biodiversity Soil carbon and soil restoration determined by site-specific processes Land use Climate Overview: soil restoration and soil carbon

  3. Soil organic carbon (SOC) Physical – controls aggregate stability, aeration, water storage Chemical – allows soil to hold nutrients for plant growth Biological – energy source for microbes SOC level determined by balance between interrelated factors Vegetation decomposition rates Temperature and moisture regimes Land management Where SOC is low, land management that increases SOC is linked to restoration of degraded soil (Parshotam and Hewitt 1995, Lal 2003, Kong et al. 2005) Soil restoration and soil carbon

  4. Rates of carbon cycling, SOC pools Fast turnover Plant matter Biomass Slow turnover Humus Positive correlation between humus and aggregate stability (Drogovoz 1994, Hernanz et al. 2002, Sevink et al. 2005) Soil restoration and soil carbon aggregate stability AS = 1.67SOC - 8.6 r2 = 0.62 SOC Modified from Hernanz et al. 2002

  5. Soil type - Alfisols • Arkose pedisediment • Well-drained • Topsoil • SOC stored in upper horizon • Varying texture, clay content image source: CSIC-CCMA

  6. Chemical mining of soil fertility and loss of nutrients Biological decline of soil microbes Physical lowered aggregate stability from tillage crusting and redistribution of topsoil Soil degradation Lower image source: CSIC-CCMA

  7. Soil carbon cycling models • Models • SOCRATES: southern Australia (P. Grace) • RothC: northeast United Kingdom (D. Jenkinson, K. Coleman) • Applied in range of ecosystems • Semi-arid systems in U.S., Europe and Australia • Range of SOC values • Benefits • Calculate changes for different SOC pools over long time scales • Can be used to predict outcome of land use and climate change • Crop yields (SOCRATES)

  8. SOCRATES 1:1 line r2 = 0.90

  9. Scenario comparison: SOCRATES • CP: Continuous pasture • T: Traditional cereal rotation • P5: 5 year pasture, 5 year cereal rotations • P10: 10 year pasture, 5 year cereal rotations

  10. Scenario comparison: SOC

  11. Scenario comparison: Humus

  12. Scenario comparison: Grain yields

  13. Conclusions and application • Longer pasture rotation positively correlated with: • Improved humus conditions • Increased aggregate stability • Crop yields • Longer pasture could present policy-makers with win-win scenarios • Restoration of soil • Maintained crop output

  14. Acknowledgements • Bridgewater State College Center and the Advancement of Teaching and Research. • Senior research scientists Dr. Gerardo Benito and Dr. Gonzalo Almendros and Carlos LaCasta, manager of La Higuerela experimental farm • The Centro de Ciencias Medioambientales, part of the Consejo Superior de Investigaciones Cientificas in Madrid, Spain for sharing their data sources.

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