Global patterns of nitrate storage in the vadose zone

Ascott, Matthew; Gooddy, Daren C.; Wang, L; Stuart, Marianne; Lewis, Melinda; Ward, Rob; Binley, Andrew

doi:10.1038/s41467-017-01321-w

Cited by 289 publications

(202 citation statements)

References 60 publications

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“…These model-based reference points include the vegetation N pool, values by a factor of 5 and underestimate NH + 4 values by a factor of 2 in the soil. The accumulation of NO − 3 in lower soil layers is a phenomenon also reported by Walvoord et al (2003) and Ascott et al (2017). In any case, this nitrogen pool is largely inaccessible to plants, as they have very little root access to these layers in our model.…”

Section: N Pools and Fluxesmentioning

confidence: 49%

Implementing the nitrogen cycle into the dynamic global vegetation, hydrology, and crop growth model LPJmL (version 5.0)

et al. 2018

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Abstract. The well-established dynamical global vegetation, hydrology, and crop growth model LPJmL is extended with a terrestrial nitrogen cycle to account for nutrient limitations. In particular, processes of soil nitrogen dynamics, plant uptake, nitrogen allocation, response of photosynthesis and maintenance respiration to varying nitrogen concentrations in plant organs, and agricultural nitrogen management are included in the model. All new model features are described in full detail and the results of a global simulation of the historic past ) are presented for evaluation of the model performance. We find that the implementation of nitrogen limitation significantly improves the simulation of global patterns of crop productivity. Regional differences in crop productivity, which had to be calibrated via a scaling of the maximum leaf area index, can now largely be reproduced by the model, except for regions where fertilizer inputs and climate conditions are not the yield-limiting factors. Furthermore, it can be shown that land use has a strong influence on nitrogen losses, increasing leaching by 93 %.

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Section: N Pools and Fluxesmentioning

confidence: 49%

Implementing the nitrogen cycle into the dynamic global vegetation, hydrology, and crop growth model LPJmL (version 5.0)

et al. 2018

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“…Subsequently, this method was implemented within a statistical framework based on GIS variables to reduce model complexity (Nolan et al, ). Recently, Ascott et al () adopted a simplistic nitrate budgeting model that permitted the computation of vadose zone nitrate storage on a global scale. The results calculated from such budget models could be tested against the multiple column approach calculations.…”

Section: Discussion and Future Researchmentioning

confidence: 99%

“…Recently, Ascott et al (2017) adopted a simplistic nitrate budgeting model that permitted the computation of vadose zone nitrate storage on a global scale. The results calculated from such budget models could be tested against the multiple column approach calculations.…”

Section: Water Resources Researchmentioning

confidence: 99%

Recharge and Nitrate Transport Through the Deep Vadose Zone of the Loess Plateau: A Regional‐Scale Model Investigation

Turkeltaub

Jia

Zhu

et al. 2018

Water Resources Research

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The Loess Plateau of China (LPC) is suffering from the impacts of overexploitation of groundwater, leading to a decline in the regional water table. This is compounded by relatively recent large‐scale transformation of land use, which may impact groundwater recharge and threaten future water quality from intensive nitrogen fertilizer application. Understanding the regional unsaturated water flow and nitrate travel time in the deep vadose zone is crucial for the sustainable management of the LPC groundwater system. We develop here a regional‐scale model that exploits an extensive database of soil properties derived from recent intensive soil profile sampling over the LPC, together with climate, vadose zone thickness, and land use data. The model solves the Richards equation and a conservative solute transport model using a multiple 1D column approach. A comparison between model simulations and observations at five sites reveals good model performance. Application over the LPC indicates that areas with dense irrigated agricultural land use contribute significantly to groundwater recharge. By using land use cover information from 1975 to 2008, simulations reveal that the transition from agriculture to forest and grassland accounts for a small reduction of the total annual recharge (6.1%). Modeled nitrate travel times through the deep unsaturated zone range between decades and centuries; however, recent loading of anthropogenic nitrate is expected to reach the aquifer in the near future under irrigated areas or where the vadose zone is relatively thin. The model simulations provide valuable information for assessing future vulnerability of groundwater resources over a regional scale.

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“…Denitrification in the unsaturated zone is limited by low water contents and oxic conditions, resulting in substantial stores of NO3 -in vadose zones (Turkeltaub et al, 2016;Ascott et al, 2017). NO3 -in water that is removed rapidly from site is 5 also unlikely to be substantially attenuated by denitrification due to oxic conditions and rapid transit times (Ernstsen et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

Sources and fate of nitrate in groundwater at agricultural operations overlying glacial sediments

Bourke¹,

Iwanyshyn²,

Köhn³

et al. 2018

Preprint

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for using a Monte Carlo approach. When denitrification could be quantified, we reconstructed the initial NO3-N concentration and NO3-N/Cl -ratio at the point of entry to the groundwater system. The addition of NO3 -to the local groundwater system from temporary manure piles and pens equalled or exceeded NO3 -additions due to leaching from earthen manure storages at these sites. Nitrate attenuation at both sites is attributed to a spatially 20 variable combination of mixing and denitrification, but is dominated by denitrification. On-site denitrification reduced agriculturally derived NO3 -concentrations by at least half and, in some wells, completely. These results indicate that infiltration to groundwater systems in glacial sediments where NO3 -can be naturally attenuated is likely preferable to off-farm export via runoff or drainage networks. The application of isotopes of nitrate to constrain a mixing model based on concentrations of Cl -and NO3 -, which can be routinely monitored in 25 groundwater, provides a relatively simple method to assess the sources and fate of agriculturally derived NO3 -in these settings.

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Global patterns of nitrate storage in the vadose zone

Cited by 289 publications

References 60 publications

Implementing the nitrogen cycle into the dynamic global vegetation, hydrology, and crop growth model LPJmL (version 5.0)

Implementing the nitrogen cycle into the dynamic global vegetation, hydrology, and crop growth model LPJmL (version 5.0)

Recharge and Nitrate Transport Through the Deep Vadose Zone of the Loess Plateau: A Regional‐Scale Model Investigation

Sources and fate of nitrate in groundwater at agricultural operations overlying glacial sediments

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