Submitted to: CRC Press
Publication Type: Book / Chapter
Publication Acceptance Date: 3/20/2007
Publication Date: 7/15/2008
Citation: Wang, P., Sadeghi, A., Linker, L., Arnold, J., Shenk, G., Wu, J. 2008. Simulated soil water content effect on plant nitrogen uptake and export for watershed management. In: Ma, L., Ahuja, L.R., Brusselma, T., editors. Quantifying and Understanding Plant Nitrogen Uptake for Systems Modeling. Boca Raton, FL: Taylor & Francis Group, LLC. p. 277-304. Interpretive Summary: Plant N uptake is controlled by plant demand on nitrogen, the availability of nitrogen in soil, and dissolved inorganic nitrogen in soil water solution. The plant N uptake simulation in the current SWAT and the HSPF target-based methods considers plant demand on nitrogen, but lack of consideration of DIN concentration and soil moisture effect. The consideration of the latter improves the simulation of DIN uptake and export. The Michaelis-Menten method of plant uptake considers DIN concentration and moisture effect, besides its consideration of plant N demand. The synthetic method of plant N uptake that uses mass as the unit for plant maximum uptake rate for both above and below field capacity by Wang and Linker (2006) can well simulate plant nitrogen uptake.
Technical Abstract: In watershed nutrient management for water quality assessment, it is important to understand the critical pathways of nutrient cycles and nutrient transport processes from lands to the receiving water bodies. Soil moisture content influences plant nitrogen uptake significantly. This paper discussed the improvement of computer simulation in plant nitrogen uptake by considering soil moisture effect for the SWAT plant nitrogen uptake module, the HSPF target-based uptake module, and the HSPF Michaelis-Menten plant uptake module. Preliminary simulation results show that both the initial SWAT and the modified SWAT can simulate well in plant N uptake and biomass accumulation, whereas, the modified SWAT improves the simulate over the initial SWAT. The improvement of nitrogen uptake in turn improves simulation of dissolved inorganic nitrogen export. This paper also discusses the importance in the selection of unit of maximum uptake rate in the Michaelis-Menten equation.