Notes
Slide Show
Outline
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Nitrous Oxide Losses Are Increased
Under No-Tillage and Early Fertilization


Ivy Tan1, Harold van Es1, John Duxbury1, Larry Geohring2, Robert Schindelbeck1, Jeff Melkonian1, and Dean Hively1

 1 Department of Crop and Soil Sciences, Cornell University
 2 Department of Biological and Environmental Engineering, Cornell University








 Supported by the Agricultural Ecosystems Program and the Initiative on Computational Agriculture
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Nitrogen as a Greenhouse Gas
  • N2O is generated by the nitrification and denitrification processes and is a potent greenhouse gas (310 times CO2) that also harms the ozone layer.
  • Anaerobic conditions in agricultural soils promote high denitrification rates:              NO3        NO2     NO      N2O        N2
  • N2O emissions are currently poorly quantified and the effects of management practices, especially tillage and N application timing, on those emissions are largely unknown.
  • Inconclusive data in the literature suggest that increased N2O losses may partially offset the reduced CO2 losses from no-tillage compared to conventional tillage.
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Objectives
  • Determine greenhouse gas impact of tillage and N management practices during the critical late-spring period
  • Hypotheses to test:
    • Soils with finer texture have greater N2O loss
    • Early N fertilization poses higher risk for N2O fluxes than late fertilization
    • No till increases N2O emissions
    • Crop rotation affects N2O fluxes
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Plot Locations
  • Willsboro Farm with two soil types
    • Loamy sand
    • Clay loam
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Experimental Design
  •         Maize               Maize             Maize               Maize
  •    After Grass      After Maize    After Grass      After Maize
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Gas Chamber Placement in Plots
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N2O Sampling
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Soil and Water Sampling
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Muskellunge Clay Loam
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Stafford Loamy Sand
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Analysis of Variance for Response on Cumulative N2O Flux
    •                 Significance Level
    • Soil           ***
    • Tillage            **
    • NTreatment            ***
    • Rotation           *
    • Soil x Tillage             *
    • Soil x NTreatment             **
    • Tillage x NTreatment             *
    • Soil x Tillage x NTreatment           *


    • *     p-value ≤ 0.1
    • **   p-value ≤ 0.05
    • *** p-value ≤ 0.01
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Summary of Results
Cumulative N2O Loss (kg N/ha)
Muskellunge Clay Loam
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Soil Porosity
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Partial Budget
CO2 Equivalent Losses (kg CO2e ha-1 yr-1)
No Till vs. Plow Till, Early vs. Late Fertilization
Muskellunge Clay Loam
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Conclusions
  • N2O fluxes from denitrification are greater for clay loam than loamy sand soils and very significant in terms of GHG impact
  • N2O losses are strongly affected by interactions of rotation, tillage, and timing of N application. Carbon availability is apparently a significant determinant for N2O losses.
  • The increased N2O losses under no till may negate the benefits of C sequestration unless N fertilizer application is optimally timed. In fact, GHG impact may be greatly increased.
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Next Steps
  • Improve the Precision Nitrogen Management model calibration for the critical spring period precipitation events
  • Perform model simulations on multiple-year data to assess effects of different mitigation strategies on N management on environmental and economic aspects