Song et al. (2026) Simulation of Nitrogen Migration and Output Loads Under Field Scale in Small Watershed, China

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Identification

• Journal: Land
• Year: 2026
• Date: 2026-03-10
• Authors: Yixiao Song, Ling Jiang, Ming Liang
• DOI: 10.3390/land15030442

Research Groups

[Not specified in the provided text.]

Short Summary

This study investigated nitrogen transport dynamics in an agricultural watershed using high-resolution UAV-derived digital elevation models (DEMs) and coupled hydrological–erosion modeling. It found that decimeter-scale DEMs are essential for accurately capturing microtopographic regulation, which predominantly controls nitrogen migration and spatial heterogeneity of exports.

Objective

• To quantify nitrogen transport dynamics and migration mechanisms in a small agricultural watershed, specifically assessing the role of microtopographic heterogeneity and the impact of DEM resolution on simulation accuracy.

Study Configuration

• Spatial Scale: 1.27 km² agricultural watershed in China’s Jianghuai region.
• Temporal Scale: Annual (for nitrogen output loads).

Methodology and Data

• Models used: Soil Conservation Service Curve Number (SCS-CN), Modified Universal Soil Loss Equation (MUSLE), multi-flow direction algorithm, Structural Equation Modeling.
• Data sources: Unmanned aerial vehicle (UAV)-derived 0.1 m digital elevation models (DEMs).

Main Results

• Nitrogen exports exhibited strong spatial heterogeneity (watershed mean: 29.66 kg TN/(km²·a)).
• Bare land and greenhouses showed the highest nitrogen outputs (448.54 kg/(km²·a) and 363.41 kg/(km²·a), respectively), while forested areas had minimal export (<6.1 kg/(km²·a)).
• Nitrogen migration was primarily controlled by topographic gradients, with microtopographic features (field ridges, ditches, buildings) physically redirecting flows and creating critical export nodes at field boundaries.
• DEM resolution critically affected simulation accuracy; erosion intensity showed a non-monotonic response with an inflection point near 1 m resolution, corresponding to the median elevation difference (1.2 m) of field ridges.
• High-resolution DEMs (0.1–2 m) maintained strong topographic control over nitrogen migration (~80% contribution), whereas 30 m DEMs reduced this influence to 30%, leading to spurious meteorological dominance.

Contributions

• Demonstrates the critical importance of decimeter-scale DEMs for accurately capturing microtopographic regulation of nitrogen transport in agricultural watersheds.
• Provides a methodological basis for precision management of agricultural non-point source pollution by highlighting the necessity of high-resolution topographic data.
• Quantifies the spatial heterogeneity of nitrogen exports at the field scale and identifies key controlling factors (topography, land use).

Funding

[Not specified in the provided text.]

Citation

@article{Song2026Simulation,
  author = {Song, Yixiao and Jiang, Ling and Liang, Ming},
  title = {Simulation of Nitrogen Migration and Output Loads Under Field Scale in Small Watershed, China},
  journal = {Land},
  year = {2026},
  doi = {10.3390/land15030442},
  url = {https://doi.org/10.3390/land15030442}
}