Topography, Soil Elemental Stoichiometry and Landscape Structure Determine the Nitrogen and Phosphorus Loadings of Agricultural Catchments in the Subtropics

Yong Li (), Yi Wang, Ji Liu, Meihui Wang, Jianlin Shen and Xinliang Liu
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Yong Li: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Yi Wang: College of Resources and Environmental Engineering, Ludong University, Yantai 264025, China
Ji Liu: Key Laboratory of Agro-Ecological Processes in Subtropical Regions and Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
Meihui Wang: College of Geography, Nanning Normal University, Nanning 530011, China
Jianlin Shen: Key Laboratory of Agro-Ecological Processes in Subtropical Regions and Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
Xinliang Liu: Key Laboratory of Agro-Ecological Processes in Subtropical Regions and Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China

Land, 2023, vol. 12, issue 3, 1-21

Abstract: The control of nitrogen (N) and phosphorus (P) loadings to receiving waters is often overcompensated for by catchment planners. The objectives of this study, which investigated nine catchments in the subtropics of China, were to (i) quantify the explicit relationships between the N and P loadings to receiving waters and the topographic, soil and landscape characteristics of catchments, (ii) identify key impact factors and (iii) identify the most influential N and P loading pathways via catchments. Our collective data indicated that elevation–relief ratio, soil elemental stoichiometry and landscape structure determined the N and P loadings of the studied agricultural catchments. The N export from catchments characterized by a woodland backdrop (Masson pine) mosaic with the intrusion of paddy fields in the subtropics was postulated to be driven by two simultaneous processes: discharge and retention. In addition, a soil C:P threshold ratio for the catchment N and P loadings was estimated to be in the range of 107–117. Our PLS-SEM path analyses suggested that to reduce the N export from agricultural catchments in the subtropics, mitigation practices in landscape ecosystems (e.g., landscape patterns, ditches and streams) need to be taken into consideration and predominantly deployed, despite traditional measures used for soils. Strategies to lower the catchment P export can be directly proposed at the source site. Our findings provide greater insights into the transport and retention of N and P nutrients through catchments and may optimally direct the focus of catchment planners, thus increasing the control efficacy of catchment N and P losses.

Keywords: N and P loadings; soil elemental stoichiometry; agricultural catchments; subtropics; water quality controls (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2023
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