Accumulation of nitrate and dissolved organic nitrogen at depth in a red soil Critical Zone

Huayong Wu, Xiaodong Song, Xiaorui Zhao, Xinhua Peng, Hu Zhou, Paul D. Hallett, Mark E. Hodson, Gan Lin Zhang

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Nitrate accumulation has been reported in the top 1 m and subsurface soil (>1 m) across arid to semi-humid regions, but not in humid regions. Nitrate inventories through the whole regolith, referred to collectively as soil and saprolite, in humid regions have received little attention to date, likely due to previously assumed low nitrification rates and large nitrogen (N) losses by severe surface runoff and erosion. In order to understand if and how reactive N exists in the below ground (soil and saprolite) in humid environment, the amount of NO3 -N, NH4 +-N and dissolved organic N (DON) present in the regolith to a depth of 9 m in a typical red soil Critical Zone was investigated under different land uses (upland, woodland and paddy field). The Red Soil Critical Zone Observatory is located in the subtropical Jiangxi Province, China, with a mean annual precipitation of 1795 mm and mean annual potential evapotranspiration of 1229 mm. The examined regoliths were acidic, highly weathered, and mainly clay loam to clay in texture. Results showed that on average 92% (827 ± 97 kg N ha−1) of NO3 -N and 82% (521 ± 153 kg N ha−1) of DON were stored at depth (from a depth of 1 m to the bedrock surface) in the upland regolith, while 92% (283 kg N ha−1) of NO3 -N and 78% (820 kg N ha−1) of DON were stored at depth in the woodland regolith. Nitrate N significantly accumulated with depth in the upland regolith from the 1- to 4-m depth interval (p < 0.01), while the inventory (632 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 71% of the total. Dissolved organic N significantly accumulated with depth in the upland regolith from the 0- to 3-m depth interval (p < 0.01), while the inventory (408 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 64% of the total. There was no significant accumulation for NH4 +-N throughout the upland regolith (p = 0.35). No substantial accumulation of dissolved N was measured at depth in paddy field regoliths with different cultivation ages. The finding that large reservoirs of reactive N can exist in deep regolith rather than in the routinely investigated solum of subtropical regions shows a missing part of the terrestrial N budget and raises concerns about potential groundwater nitrate pollution.

Original languageEnglish
Pages (from-to)1175-1185
Number of pages11
JournalGeoderma
Volume337
Early online date23 Nov 2018
DOIs
Publication statusPublished - 1 Mar 2019

Fingerprint

dissolved organic nitrogen
red soil
regolith
nitrates
nitrate
highlands
soil
saprolite
paddy field
paddies
woodlands
woodland
clay
humid environment
China
subtropical region
potential evapotranspiration
clay loam
bedrock
subtropics

Keywords

  • Critical Zone Observatory
  • Dissolved organic nitrogen
  • Nitrate accumulation
  • Porosity
  • Red soil
  • CHINA
  • DEPOSITION
  • RISK
  • CONTAMINATION
  • TRENDS
  • CENTRAL-VALLEY
  • REACTIVE NITROGEN
  • NITRIFICATION
  • DRINKING-WATER NITRATE
  • GROUNDWATER

ASJC Scopus subject areas

  • Soil Science

Cite this

Accumulation of nitrate and dissolved organic nitrogen at depth in a red soil Critical Zone. / Wu, Huayong; Song, Xiaodong; Zhao, Xiaorui; Peng, Xinhua; Zhou, Hu; Hallett, Paul D.; Hodson, Mark E.; Zhang, Gan Lin.

In: Geoderma, Vol. 337, 01.03.2019, p. 1175-1185.

Research output: Contribution to journalArticle

Wu, Huayong ; Song, Xiaodong ; Zhao, Xiaorui ; Peng, Xinhua ; Zhou, Hu ; Hallett, Paul D. ; Hodson, Mark E. ; Zhang, Gan Lin. / Accumulation of nitrate and dissolved organic nitrogen at depth in a red soil Critical Zone. In: Geoderma. 2019 ; Vol. 337. pp. 1175-1185.
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abstract = "Nitrate accumulation has been reported in the top 1 m and subsurface soil (>1 m) across arid to semi-humid regions, but not in humid regions. Nitrate inventories through the whole regolith, referred to collectively as soil and saprolite, in humid regions have received little attention to date, likely due to previously assumed low nitrification rates and large nitrogen (N) losses by severe surface runoff and erosion. In order to understand if and how reactive N exists in the below ground (soil and saprolite) in humid environment, the amount of NO3 −-N, NH4 +-N and dissolved organic N (DON) present in the regolith to a depth of 9 m in a typical red soil Critical Zone was investigated under different land uses (upland, woodland and paddy field). The Red Soil Critical Zone Observatory is located in the subtropical Jiangxi Province, China, with a mean annual precipitation of 1795 mm and mean annual potential evapotranspiration of 1229 mm. The examined regoliths were acidic, highly weathered, and mainly clay loam to clay in texture. Results showed that on average 92{\%} (827 ± 97 kg N ha−1) of NO3 −-N and 82{\%} (521 ± 153 kg N ha−1) of DON were stored at depth (from a depth of 1 m to the bedrock surface) in the upland regolith, while 92{\%} (283 kg N ha−1) of NO3 −-N and 78{\%} (820 kg N ha−1) of DON were stored at depth in the woodland regolith. Nitrate N significantly accumulated with depth in the upland regolith from the 1- to 4-m depth interval (p < 0.01), while the inventory (632 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 71{\%} of the total. Dissolved organic N significantly accumulated with depth in the upland regolith from the 0- to 3-m depth interval (p < 0.01), while the inventory (408 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 64{\%} of the total. There was no significant accumulation for NH4 +-N throughout the upland regolith (p = 0.35). No substantial accumulation of dissolved N was measured at depth in paddy field regoliths with different cultivation ages. The finding that large reservoirs of reactive N can exist in deep regolith rather than in the routinely investigated solum of subtropical regions shows a missing part of the terrestrial N budget and raises concerns about potential groundwater nitrate pollution.",
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author = "Huayong Wu and Xiaodong Song and Xiaorui Zhao and Xinhua Peng and Hu Zhou and Hallett, {Paul D.} and Hodson, {Mark E.} and Zhang, {Gan Lin}",
note = "This study was financially supported by the National Natural Science Foundation of China (41571130051; 41501228; 41771251) and by the Frontier Program of the Institute of Soil Science, Chinese Academy of Sciences (ISSASIP1625). This research was part of the China-UK Red Soil Critical Zone project co-financed by the Natural Environment Research Council (NERC: NE/N007611/1; NE/N007484/1) under the Newton Fund scheme. We would like to thank the editor and anonymous reviewers for their thoughtful comments that have greatly improved our manuscript.",
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T1 - Accumulation of nitrate and dissolved organic nitrogen at depth in a red soil Critical Zone

AU - Wu, Huayong

AU - Song, Xiaodong

AU - Zhao, Xiaorui

AU - Peng, Xinhua

AU - Zhou, Hu

AU - Hallett, Paul D.

AU - Hodson, Mark E.

AU - Zhang, Gan Lin

N1 - This study was financially supported by the National Natural Science Foundation of China (41571130051; 41501228; 41771251) and by the Frontier Program of the Institute of Soil Science, Chinese Academy of Sciences (ISSASIP1625). This research was part of the China-UK Red Soil Critical Zone project co-financed by the Natural Environment Research Council (NERC: NE/N007611/1; NE/N007484/1) under the Newton Fund scheme. We would like to thank the editor and anonymous reviewers for their thoughtful comments that have greatly improved our manuscript.

PY - 2019/3/1

Y1 - 2019/3/1

N2 - Nitrate accumulation has been reported in the top 1 m and subsurface soil (>1 m) across arid to semi-humid regions, but not in humid regions. Nitrate inventories through the whole regolith, referred to collectively as soil and saprolite, in humid regions have received little attention to date, likely due to previously assumed low nitrification rates and large nitrogen (N) losses by severe surface runoff and erosion. In order to understand if and how reactive N exists in the below ground (soil and saprolite) in humid environment, the amount of NO3 −-N, NH4 +-N and dissolved organic N (DON) present in the regolith to a depth of 9 m in a typical red soil Critical Zone was investigated under different land uses (upland, woodland and paddy field). The Red Soil Critical Zone Observatory is located in the subtropical Jiangxi Province, China, with a mean annual precipitation of 1795 mm and mean annual potential evapotranspiration of 1229 mm. The examined regoliths were acidic, highly weathered, and mainly clay loam to clay in texture. Results showed that on average 92% (827 ± 97 kg N ha−1) of NO3 −-N and 82% (521 ± 153 kg N ha−1) of DON were stored at depth (from a depth of 1 m to the bedrock surface) in the upland regolith, while 92% (283 kg N ha−1) of NO3 −-N and 78% (820 kg N ha−1) of DON were stored at depth in the woodland regolith. Nitrate N significantly accumulated with depth in the upland regolith from the 1- to 4-m depth interval (p < 0.01), while the inventory (632 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 71% of the total. Dissolved organic N significantly accumulated with depth in the upland regolith from the 0- to 3-m depth interval (p < 0.01), while the inventory (408 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 64% of the total. There was no significant accumulation for NH4 +-N throughout the upland regolith (p = 0.35). No substantial accumulation of dissolved N was measured at depth in paddy field regoliths with different cultivation ages. The finding that large reservoirs of reactive N can exist in deep regolith rather than in the routinely investigated solum of subtropical regions shows a missing part of the terrestrial N budget and raises concerns about potential groundwater nitrate pollution.

AB - Nitrate accumulation has been reported in the top 1 m and subsurface soil (>1 m) across arid to semi-humid regions, but not in humid regions. Nitrate inventories through the whole regolith, referred to collectively as soil and saprolite, in humid regions have received little attention to date, likely due to previously assumed low nitrification rates and large nitrogen (N) losses by severe surface runoff and erosion. In order to understand if and how reactive N exists in the below ground (soil and saprolite) in humid environment, the amount of NO3 −-N, NH4 +-N and dissolved organic N (DON) present in the regolith to a depth of 9 m in a typical red soil Critical Zone was investigated under different land uses (upland, woodland and paddy field). The Red Soil Critical Zone Observatory is located in the subtropical Jiangxi Province, China, with a mean annual precipitation of 1795 mm and mean annual potential evapotranspiration of 1229 mm. The examined regoliths were acidic, highly weathered, and mainly clay loam to clay in texture. Results showed that on average 92% (827 ± 97 kg N ha−1) of NO3 −-N and 82% (521 ± 153 kg N ha−1) of DON were stored at depth (from a depth of 1 m to the bedrock surface) in the upland regolith, while 92% (283 kg N ha−1) of NO3 −-N and 78% (820 kg N ha−1) of DON were stored at depth in the woodland regolith. Nitrate N significantly accumulated with depth in the upland regolith from the 1- to 4-m depth interval (p < 0.01), while the inventory (632 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 71% of the total. Dissolved organic N significantly accumulated with depth in the upland regolith from the 0- to 3-m depth interval (p < 0.01), while the inventory (408 ± 75 kg N ha−1) in the top 3-m zone accounted for on average 64% of the total. There was no significant accumulation for NH4 +-N throughout the upland regolith (p = 0.35). No substantial accumulation of dissolved N was measured at depth in paddy field regoliths with different cultivation ages. The finding that large reservoirs of reactive N can exist in deep regolith rather than in the routinely investigated solum of subtropical regions shows a missing part of the terrestrial N budget and raises concerns about potential groundwater nitrate pollution.

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KW - Porosity

KW - Red soil

KW - CHINA

KW - DEPOSITION

KW - RISK

KW - CONTAMINATION

KW - TRENDS

KW - CENTRAL-VALLEY

KW - REACTIVE NITROGEN

KW - NITRIFICATION

KW - DRINKING-WATER NITRATE

KW - GROUNDWATER

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