1 / 15

Toby Ahrens 26 Oct 2004

Linking Spatial Variability of Soil N Retention Mechanisms to Landscape-level Fates in Yaqui Valley, Mexico. Toby Ahrens 26 Oct 2004. Goals. Quantify degrees of N contamination under different management regimes Investigate the value of spatial data sets varying in resolution

sofia
Download Presentation

Toby Ahrens 26 Oct 2004

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Linking Spatial Variability of Soil N Retention Mechanisms to Landscape-level Fates in Yaqui Valley, Mexico Toby Ahrens 26 Oct 2004

  2. Goals • Quantify degrees of N contamination under different management regimes • Investigate the value of spatial data sets varying in resolution • Integrate 10+ yrs of biogeochemistry research in the Valley

  3. What do I need to do to get there? • Link process and transport models • Improve process models • Include abiotic retention mechanisms • Develop spatial data sets • Eg. soil type, texture, mineralogy, management, leaching potential

  4. Coastal eutrophication Declassified Keyhole satellite image March 8, 1978 (Thanks Mike!)

  5. Nitrate-contaminated groundwater <10 ppm 10-40 ppm 116 ppm Hungate, unpublished data, 1997-98

  6. Two Q’s guiding my efforts: • What soil characteristics control N availability, retention and loss in OM-deficient ag soils? • Can the spatial variability of these characteristics be linked to aqueous N fates throughout the Valley?

  7. Model schematic… soil properties soil mineralogy crop yield (+N use) management unit crop type groundwater depth NLOSS Solute transport un/saturated boundary conditions • Output maps: • Leaching vulnerability • Aquifer contamination • Coastal N sources

  8. Lee Addams’s model

  9. Major modeling efforts: • Soil submodel including sorption isotherms and mineral fixation • Solute transport component to saturated hydrology model • Saturated/unsaturated boundary layer conditions • Spatial data referencing

  10. Applied N: 250 kg/ha Gaseous losses: NO+N2O: 2-5% NH3: __% N2: __% Plant uptake: 31% Drainage canals: NO3- + NH4+: 2-5% NO+N2O: <0.1% ? Leached: 2-5% (14-26%) ? ? References: Riley et al. 2001 Harrison 2003 Matson et al. 1998 Ortiz-Monasterio, pers. comm. ?

  11. Applied N: 250 kg/ha Gaseous losses: NO+N2O: 2-5% NH3: __% N2: __% Plant uptake: 31% Drainage canals: NO3- + NH4+: 2-5% NO+N2O: <0.1% ? Leached: 2-5% (14-26%) • Field experiments: • abiotic fixation • link leaching potential • to actual fates ? ? ?

  12. Future directions and broader implications… • Does better spatial resolution increase our ability to predict SW/GW vulnerability? • And the degree of how mechanistic submodels are? • Identify thresholds for N retention • Or pesticides… • Investigate management scenarios • Different irrigation or fertilization regimes

  13. Resolution of input data:Field based…

  14. Policy implications • The Danish and Dutch experiences: • N control policies aimed at reducing N leaching (SW + GW) and NH3 and N2O emissions • Importance of model validation

More Related