The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes
Watershed and global-scale nitrogen (N) budgets indicate that the majority of the N surplus in anthropogenic landscapes does not reach the coastal oceans. While there is general consensus that this ‘missing’ N either exits the landscape via denitrification or is retained within watersheds as nitrate...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2016-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/11/3/035014 |
| _version_ | 1797748564752859136 |
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| author | K J Van Meter N B Basu J J Veenstra C L Burras |
| author_facet | K J Van Meter N B Basu J J Veenstra C L Burras |
| author_sort | K J Van Meter |
| collection | DOAJ |
| description | Watershed and global-scale nitrogen (N) budgets indicate that the majority of the N surplus in anthropogenic landscapes does not reach the coastal oceans. While there is general consensus that this ‘missing’ N either exits the landscape via denitrification or is retained within watersheds as nitrate or organic N, the relative magnitudes of these pools and fluxes are subject to considerable uncertainty. Our study, for the first time, provides direct, large-scale evidence of N accumulation in the root zones of agricultural soils that may account for much of the ‘missing N’ identified in mass balance studies. We analyzed long-term soil data (1957–2010) from 2069 sites throughout the Mississippi River Basin (MRB) to reveal N accumulation in cropland of 25–70 kg ha ^−1 yr ^−1 , a total of 3.8 ± 1.8 Mt yr ^−1 at the watershed scale. We then developed a simple modeling framework to capture N depletion and accumulation dynamics under intensive agriculture. Using the model, we show that the observed accumulation of soil organic N (SON) in the MRB over a 30 year period (142 Tg N) would lead to a biogeochemical lag time of 35 years for 99% of legacy SON, even with complete cessation of fertilizer application. By demonstrating that agricultural soils can act as a net N sink, the present work makes a critical contribution towards the closing of watershed N budgets. |
| first_indexed | 2024-03-12T16:06:35Z |
| format | Article |
| id | doaj.art-751ae9fcd7374ade863b6f19e8caf631 |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T16:06:35Z |
| publishDate | 2016-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-751ae9fcd7374ade863b6f19e8caf6312023-08-09T14:18:54ZengIOP PublishingEnvironmental Research Letters1748-93262016-01-0111303501410.1088/1748-9326/11/3/035014The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapesK J Van Meter0N B Basu1J J Veenstra2C L Burras3Department of Earth and Environmental Sciences, University of Waterloo , 200 University Avenue West, Waterloo, ON N2L 3G1, CanadaDepartment of Earth and Environmental Sciences, University of Waterloo , 200 University Avenue West, Waterloo, ON N2L 3G1, Canada; Department of Civil and Environmental Engineering, Department of Earth and Environmental Sciences, 200 University Avenue West, Waterloo, ON N2L 3G1, CanadaDepartment of Math, Science & Technology, Flagler College, 74 King St., St. Augustine, FL 32084, USADepartment of Agronomy, Iowa State University , 2104 Agronomy Hall, Ames, IA 50011, USAWatershed and global-scale nitrogen (N) budgets indicate that the majority of the N surplus in anthropogenic landscapes does not reach the coastal oceans. While there is general consensus that this ‘missing’ N either exits the landscape via denitrification or is retained within watersheds as nitrate or organic N, the relative magnitudes of these pools and fluxes are subject to considerable uncertainty. Our study, for the first time, provides direct, large-scale evidence of N accumulation in the root zones of agricultural soils that may account for much of the ‘missing N’ identified in mass balance studies. We analyzed long-term soil data (1957–2010) from 2069 sites throughout the Mississippi River Basin (MRB) to reveal N accumulation in cropland of 25–70 kg ha ^−1 yr ^−1 , a total of 3.8 ± 1.8 Mt yr ^−1 at the watershed scale. We then developed a simple modeling framework to capture N depletion and accumulation dynamics under intensive agriculture. Using the model, we show that the observed accumulation of soil organic N (SON) in the MRB over a 30 year period (142 Tg N) would lead to a biogeochemical lag time of 35 years for 99% of legacy SON, even with complete cessation of fertilizer application. By demonstrating that agricultural soils can act as a net N sink, the present work makes a critical contribution towards the closing of watershed N budgets.https://doi.org/10.1088/1748-9326/11/3/035014nitrogennutrientstime lagswater qualityretentionsoil |
| spellingShingle | K J Van Meter N B Basu J J Veenstra C L Burras The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes Environmental Research Letters nitrogen nutrients time lags water quality retention soil |
| title | The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes |
| title_full | The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes |
| title_fullStr | The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes |
| title_full_unstemmed | The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes |
| title_short | The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes |
| title_sort | nitrogen legacy emerging evidence of nitrogen accumulation in anthropogenic landscapes |
| topic | nitrogen nutrients time lags water quality retention soil |
| url | https://doi.org/10.1088/1748-9326/11/3/035014 |
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