|Gu, C - UNIV OF CALIF BERKELEY|
|Maggi, F - UNIV OF CALIF BERKELEY|
|Riley, W - LAWRENCE BERKELEY LAB|
|Hornberger, G - UNIVERSITY OF VIRGINIA|
|Xu, T - LAWRENCE BERKELEY LAB|
|Spycher, N - LAWRENCE BERKELEY LAB|
|Steefel, C - LAWRENCE BERKELEY LAB|
|Miller, N - LAWRENCE BERKELEY LAB|
|Oldenburg, C - LAWRENCE BERKELEY LAB|
Submitted to: Journal of Geophysical Research-Biogeosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 6, 2008
Publication Date: January 28, 2009
Citation: Gu, C., Maggi, F., Venterea, R.T., Riley, W.J., Hornberger, G.M., Xu, T., Spycher, N., Steefel, C., Miller, N.L., Oldenburg, C.M. 2009. Aqeuous and Gaseous Nitrogen Losses Induced by Fertilizer Application. Journal of Geophysical Research-Biogeosciences. 114:GO1006. [doi:10.1029/2008JG00788]. Interpretive Summary: The impact of nitrogen fertilizer use on water and atmospheric pollution is of growing concern. Groundwater nitrate levels in many areas exceed drinking-water standards that have been established to mitigate human health impacts (i.e., methemgloblomenia). Elevated nitrate levels in leachate and surface water can also lead to eutrophication of lakes and estuaries. Nitrous oxide (N2O) is an important greenhouse gas and is also involved in the destruction of stratospheric ozone. Nitric oxide (NO) emissions contribute to the formation of tropospheric ozone and acid deposition. NH3 emissions affect the environment in the form of wet and dry deposition of NH4 +salts, causing acidification of poorly buffered soils and eutrophication. In this study, we used a detailed mechanistic model of N biogeochemical processes (TOUGHREACT-N) to study the effects of N fertilizer types on N-losses by applying the model to a field fertilization experiment in Burgundy, France to simulate N losses following fertilizer application using different fertilizer types. Model simulations showed the importance of varying fertilizer types for N losses depends on fertilization practices and soil conditions. The results have direct implications with respect to fertilizer management practices: (i) soils receiving relatively small amounts of fertilizer (<100 kg N ha-1) produced more N emissions but slightly less N leaching from NH4+ fertilizers than NO3- fertilizers; this difference was diminished at higher fertilization rates; CO(NH2)2 may produce maximum N emissions at higher fertilization rates; (ii) soil buffering capacity dramatically increased N2O emissions and decreased N-leaching from different fertilizer types; buffering capacity did not impact NH3 volatilization; and (iii) soils with coarse texture produced much less nitrogen gas emissions from NO3- fertilizers than NH4+ fertilizers. These results have implications for improving emissions inventory methodologies, which currently rely on a constant emission factor irrespective of fertilizer types and its interaction with environmental conditions. Furthermore, the fertilizer-type specific emission factors are also a function of soil types/conditions and probably other environmental conditions. Thus, the results presented here have implications for the implementation of effective mitigation measures by scientists, producers, and regulators.
Technical Abstract: In recent years concern has grown over the contribution of nitrogen (N) fertilizers to nitrate (NO3-) water pollution and atmospheric pollution of nitrous oxide (N2O), nitric oxide (NO), and ammonia (NH3). Characterizing the amount and species of N losses is therefore essential in developing a strategy to estimate and mitigate N leaching and emission to the atmosphere. In this paper, an extant mechanistic N cycle model (TOUGHREACT-N) was tested in an experiment measuring soil N species and N2O and NO emissions after fertilization with several fertilizer types. We focus here on the period following fertilization and irrigation and prior to plant emergence. The results showed that N fertilizer type, application method, and soil type significantly affected N gas emissions and nitrate leaching rates. NH4+-N fertilizer induced much higher NO and N2O emissions and less N leaching than NO3--N fertilizers, especially in coarse- textured soils. The N2O emission from NH4+-N fertilizer was ~30 and ~6 times higher than from urea and NO3--N fertilizers, respectively. This difference increased further under conditions with lightly applied fertilization and high soil buffering capacity. In contrast to methods used to estimate global terrestrial gas emission, we found strongly non-linear N2O emissions as a function of fertilizer application rate and soil calcite content. The results highlight the need for further observations designed to test mechanistic models and of emission and leaching factors that account for fertilizer type, application method, and soil properties.