Preprints
https://doi.org/10.5194/hess-2019-666
https://doi.org/10.5194/hess-2019-666

  16 Jan 2020

16 Jan 2020

Review status: this preprint was under review for the journal HESS. A revision for further review has not been submitted.

Effect of preferential transport and coherent denitrification on leaching of nitrate to drainage

David Nagy1, Annette E. Rosenbom2, Bo V. Iversen1, and Finn Plauborg1 David Nagy et al.
  • 1Department of Agroecology, Aarhus University, Blichers Alle 20, Tjele, 8830, Denmark
  • 2Department of Geochemistry, Geological Survey of Denmark and Greenland, Oester Voldgade 10, Copenhagen K, 1350, Denmark

Abstract. To protect the quality of the aquatic environment, it is imperative to be able to assess the leaching of nitrate through various hydrogeological settings. Numerical model concepts have been developed in order to describe this leaching and possible routes of nitrogen at field scale, often without being evaluated in regard to their ability to account for dominant preferential transport and coherent denitrification, which is the rule rather than the exception in soils. This study evaluates whether it is possible to describe 10-years of nitrate concentrations, measured in drainage from a tile-drained agricultural clay till field in Denmark, by applying the soil-plant-atmosphere model DAISY, capable of accounting for preferential transport and denitrification. A DAISY model concept, including macropores capable of capturing the water and bromide balance of the field within this specific timeframe, was able to predict the water transport to drainage, dry matter and N-yield of the harvested crops, while it was unable, with the standard default denitrification model, to predict dynamics and quantity of N-loss to drainage. This was caused by a fast saturation of the plow layer, where nitrate seemed to be denitrified almost instantly, and no surplus nitrate remained to be transported to the drainage. To circumvent this and describe the measured N-loss, modification to the water reduction function affecting denitrification was conducted. The denitrification had to be reduced by approximately 50 % from a seasonal average of 75 kg N ha−1 to 35 kg N ha−1 while 48 % to 80 % of the total N-loss to drainage had to be preferentially transported from the plow layer. This study, therefore, reveals that, by not accounting for preferential transport and coherent denitrification, there is a high risk of underestimating leaching of nitrate to the aquatic environment.

David Nagy et al.

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

David Nagy et al.

David Nagy et al.

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Short summary
A large amount of N (48 % to 80 % of the total N-loss to drainage) was preferentially transported via macropores to drainage, regardless of the application method and concurrent occurrence of precipitation. Overall, this study delineates the importance of accounting for preferential transport and coherent denitrification in the assessment of the leaching risk of nitrate to the aquatic environment.