Soil water dynamics in humid tropical soils of low bulk density: correlation with N2O gas fluxes
Soils are the largest natural source of the greenhouse gas N2O. Nitrogen availability and soil moisture dynamics are the dominant flux controls in humid tropical soils. Pore water content affects N2O production and gas diffusion in soils. We used field and laboratory measured soil hydraulic properties to parameterize the HYDRUS-1D model for highly porous, low bulk density soils. From Nov 94 to Aug 96 we employed time domain reflectometry (TDR) technique and an automated chamber system for continuous measurement of water content in and N2O fluxes from agricultural soils in Costa Rica. We used time series of soil water content to evaluate simulated soil moisture dynamics. We correlated the simulated soil water content of near-surface soil with measured N2O fluxes. Highest post-fertilization fluxes (106 ng N2O - N cm-1) were measured on loam under perennial crop during a wet period. The gaseous N loss through 5 weeks after fertilization amounted to 4.9\% of the applied fertilizer. To estimate leaching losses we combined simulation results of soil water flow with nitrogen concentrations measured in pore water extracted from the soil using lysimeters. Confirming field observations, simulation results indicate that fertilization increased N loss both via leaching and as N2O gas.
EOS, Transactions American Geophysical Union, Fall Meeting, Supplement
American Geophysical Union Publications
Weitz, A., Keller, M., Crill, P. and Frolking, S., Soil water dynamics in humid tropical soils of low bulk density: correlation with N2O gas fluxes, Eos Trans. AGU, 81(48), Fall Meet. Suppl., Abstract B11C-17, 2000.