TY - JOUR
T1 - Assessment of nitrogen application limits in agro-livestock farming areas using quantile regression between nitrogen loadings and groundwater nitrate levels
AU - Kim, Ho Rim
AU - Yu, Soonyoung
AU - Oh, Junseop
AU - Kim, Kyoung Ho
AU - Oh, Yun Yeong
AU - Kim, Hyun Koo
AU - Park, Sunhwa
AU - Yun, Seong Taek
N1 - Funding Information:
This study was performed with support from a research project ( 11-1480523-002666-01 ) sponsored by the Korean Ministry of Environment (MOE) and Korea National Institute of Environmental Research (NIER) . Partial support was also provided by Korea Environment Industry & Technology Institute (KEITI) through Subsurface Environmental Management (SEM) Project, funded by Korea Ministry of Environment (MOE) ( 2018002440002 ), Basic Research Project ( GP2018-002; 19-3415 ) of the Korea Institute of Geoscience and Mineral Resources (KIGAM) funded by the Ministry of Science and ICT of Korea, and the “Korea-CO 2 Storage Environmental Management (K-COSEM) Research Program .” Thoughtful comments and suggestions from anonymous reviewers were very helpful to improve and clarify this work.
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/12/1
Y1 - 2019/12/1
N2 - The excessive application of nitrogen in agro-livestock farming areas has led to serious groundwater contamination around the world; thus, the efficient control of N loads is crucial to manage nitrate contamination of groundwater. In this study, to suggest an optimal N application limit as a key guideline of N management, we examine the impact of anthropogenic N loading on nitrate levels of shallow groundwater, using a large dataset (n = 4,000) collected in 2012–2014 from 100 agro-livestock farming districts in South Korea. Not considering the time lag and legacy problem, quantile regression is performed to overall assess the relationship between nitrate contamination and anthropogenic N input across the full range of conditional distribution of groundwater nitrate concentrations because of heteroscedasticity. As a result, positive gradients (βτ) meaning the rates of changes are found between groundwater nitrate concentrations and land-derived N loads at all quantiles; βτ increases as the quantile is higher and is as large as 36.48 ± 10.73 mg NO3 −/L per land-derived N input (on a log scale) at the 90% quantile. The quantile map indicates that the high gradient (i.e., the large sensitivity to N loading) is related to agricultural land use, low elevation, and low topographic slopes. In fact, groundwater nitrate concentrations increase as the percentage of agricultural land increases but the percentage of forest, elevation and slope angle decreases, which suggests that land use, elevation, and slope should be considered when attempting to evaluate N application limits. This study suggests the N limits below 170 kg ha-1 year-1 based on the drinking water standard (44.3 mg/L as NO3 −) at the quantiles higher than 70% which mostly occur in flat agricultural lowland areas. Our method used in this study can be applied elsewhere to establish efficient management practices for groundwater nitrate contamination, considering local environmental factors.
AB - The excessive application of nitrogen in agro-livestock farming areas has led to serious groundwater contamination around the world; thus, the efficient control of N loads is crucial to manage nitrate contamination of groundwater. In this study, to suggest an optimal N application limit as a key guideline of N management, we examine the impact of anthropogenic N loading on nitrate levels of shallow groundwater, using a large dataset (n = 4,000) collected in 2012–2014 from 100 agro-livestock farming districts in South Korea. Not considering the time lag and legacy problem, quantile regression is performed to overall assess the relationship between nitrate contamination and anthropogenic N input across the full range of conditional distribution of groundwater nitrate concentrations because of heteroscedasticity. As a result, positive gradients (βτ) meaning the rates of changes are found between groundwater nitrate concentrations and land-derived N loads at all quantiles; βτ increases as the quantile is higher and is as large as 36.48 ± 10.73 mg NO3 −/L per land-derived N input (on a log scale) at the 90% quantile. The quantile map indicates that the high gradient (i.e., the large sensitivity to N loading) is related to agricultural land use, low elevation, and low topographic slopes. In fact, groundwater nitrate concentrations increase as the percentage of agricultural land increases but the percentage of forest, elevation and slope angle decreases, which suggests that land use, elevation, and slope should be considered when attempting to evaluate N application limits. This study suggests the N limits below 170 kg ha-1 year-1 based on the drinking water standard (44.3 mg/L as NO3 −) at the quantiles higher than 70% which mostly occur in flat agricultural lowland areas. Our method used in this study can be applied elsewhere to establish efficient management practices for groundwater nitrate contamination, considering local environmental factors.
KW - Agro-livestock farming
KW - Nitrate contamination of groundwater
KW - Nitrogen application limit
KW - Nitrogen loading
KW - Quantile regression
UR - http://www.scopus.com/inward/record.url?scp=85071560387&partnerID=8YFLogxK
U2 - 10.1016/j.agee.2019.106660
DO - 10.1016/j.agee.2019.106660
M3 - Article
AN - SCOPUS:85071560387
SN - 0167-8809
VL - 286
JO - Agriculture, Ecosystems and Environment
JF - Agriculture, Ecosystems and Environment
M1 - 106660
ER -
