PARENT SESSION
Poster Session #34: Agroecology.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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Mechanistic modeling of nitrification, denitrification, soil hydrology, and N losses in an agricultural system.
Venterea, R1, Riley, W2, Rolston, D3, 1 2 3
ABSTRACT- Development of fertilizer application methods that minimize off-site N losses requires an understanding of multiple transformation pathways influencing the partitioning of applied N to various solutes and gases. We present further development of a detailed mechanistic model, called NLOSS, of biological, chemical, and physical processes which interact to determine net fluxes of N oxide gases and solutes following fertilizer applications. Previously developed models of nitrification and denitrification kinetics are coupled to mechanistic representations of transient water movement, gas diffusion, soil anaerobiosis, and pH dynamics. The model is tested by comparison to N solute concentrations and N trace gas efflux measured from intensively fertilized wheat fields in Mexico. Transient accumulations of soil nitrite (> 100 
g/g) are shown to coincide with peak nitric oxide (NO) gas fluxes of 2 mg N/m2/h. The separate contributions of nitrification and denitrification predicted by the model are compared to 15N tracer experimental results during the same field season. We expect the model to be useful together with field experimentation aimed at developing specific fertilizer application strategies for mitigating N losses as gases and leachate, while also maximizing plant availability of applied N.
KEY WORDS: n2o fluxes, no fluxes, nitrite accumulation