Abstract

Intensive agricultural land use is considered to be the major source of the anthropogenic contribution to the increase in atmospheric N2O concentration during the last decades. A reduction of anthropogenic N2O emissions therefore requires a change in agricultural management practices. Mathematical models help to understand interacting processes in the N cycle and state variables affecting N2O emissions. The aim of this study was to test two modeling approaches for their ability to describe and quantify the seasonal variations of N2O fluxes in a potato (Solanum tuberosum L.)-cropped soil. Model 1 assumes a fixed N2O/N2 ratio for N2O production and neglects the transport of N2O in the soil profile; Model 2 explicitly considers N2O transport and assumes a dynamic reduction of N2O to N2. Data for model evaluation came from an experiment where N2O fluxes were monitored during the vegetation period using a closed chamber technique. Generally, both modeling approaches were able to describe the observed seasonal dynamics of N2O emissions and events of high N2O emissions due to increased denitrification activity after heavy precipitation. The inclusion of a gas transport module in the modeling approach resulted in simulated N2O emission dynamics showing a smoother transient behavior. Extremely high emission rates from the interrow soil of the potato field were underestimated by both models. The lower N2O release from the ridge soil was mainly due to better aeration because of a lower soil bulk density and lower water contents caused by lateral runoff and root water uptake.

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