title: Comparison of APSIM and DNDC simulations of nitrogen transformations and N2O emissions.
abstract: Various models have been developed to better understand nitrogen (N) cycling in soils, which is governed by a complex interaction of physical, chemical and biological factors. Two process-based models, the Agricultural Production Systems sIMulator (APSIM) and DeNitrification DeComposition (DNDC), were used to simulate nitrification, denitrification and nitrous oxide (N2O) emissions from soils following N input from either fertiliser or excreta deposition. The effect of environmental conditions on N transformations as simulated by the two different models was compared. Temperature had a larger effect in APSIM on nitrification, whereas in DNDC, water content produced a larger response. In contrast, simulated denitrification showed a larger response to temperature and also organic carbon content in DNDC. And while denitrification in DNDC is triggered by rainfall ≥5mm/h, in APSIM, the driving factor is soil water content, with a trigger point at water content at field capacity. The two models also showed different responses to N load, with nearly linearly increasing N2O emission rates with N load simulated by DNDC, and a lower rate by APSIM. Increasing rainfall intensity decreased APSIM-simulated N2O emissions but increased those simulated by DNDC.
authors.affiliation: AgResearch Limited, Grasslands Research Centre, Private Bag 11008, Palmerston North, New Zealand. Electronic address: iris.vogeler@agresearch.co.nz.
authors.forename: I
authors.initials: I
authors.lastname: Vogeler
authors.forename: D
authors.initials: D
authors.lastname: Giltrap
authors.forename: R
authors.initials: R
authors.lastname: Cichota