<p>Land use plays a dominant role in controlling groundwater nitrogen and phosphorus contamination patterns. However, the mechanism by which land use affects nitrogen and phosphorus pollution in the Poyang Lake Basin remains unclear. We combined hydrochemical analysis, entropy-weighted water-quality indices, geostatistical modelling, positive-matrix factorization (PMF) and self-organizing maps (SOMs) to characterize the hydrochemistry, quality and spatial variability of nitrogen and phosphorus in the shallow groundwater of the western Poyang Lake region (Nanchang–Jiujiang) and to quantify their sources. HCO₃–Ca water is dominant and becomes geochemically more complex from north to south. Although the overall groundwater quality was classified as satisfactory, localized contamination hotspots were identified. High concentrations of NO₃⁻ occurred in different areas compared with high concentrations of Fe and Mn, with the latter exhibiting strong spatial coupling with urbanized regions experiencing intensive anthropogenic pressures. Total phosphorus (TP) concentrations exhibited considerable spatial variability without distinct aggregation patterns. PMF modelling attributed nitrogen mainly to agricultural fertilizers, whereas phosphorus was derived from both fertilizers and natural biogeochemical release from forest litter. Crucially, the impact of land use on groundwater quality is mediated by contaminant-specific transport pathways. This method is conducive to the optimization of groundwater protection and land use simultaneously.</p>