Spatial-Temporal Variations of Nitrogen and Phosphorus Applications and Runoff Losses in Vegetable Field in Southern China during Last Three Decades

Over the past three decades, the expansion of intensive vegetable farming in southern China has led to excessive nitrogen (N) and phosphorus (P) fertilizer application, causing substantial N and P runoff losses. This study investigated four major vegetable production regions in southern China—the upper reaches of the Yangtze River (U-YR), the middle lower reaches of the Yangtze River (ML-YR), the Southeast Coast (SC), and the Pearl River basin (PR)—analyzing 175 published articles to characterize spatiotemporal patterns of N and P fertilizer applications and associated runoff losses from 1992 to 2021. The result showed that the runoff losses of total N per year (TNy) from the U-YR and PR regions gradually increased by 141%–186% over the past three decades, while that from the other two areas decreased gradually by 17%–28%. Meanwhile, four regions generated gradually increased runoff total P per year (TPy) with 3.5%–221%. In U-YR and PR regions, the cultivated area for vegetable production increased by 68% and 28%, and the N application rates increased by 54% and 25%. Still, the soil organic matter (SOM) content decreased by 17% and 34%, respectively. However, they all showed a decreasing trend in the other two investigated regions. In the PR region, the increased planting area was attributed to newly cultivated vegetable fields, where there were serious TPy losses as the P application intensity increased by 87%. The cultivation area in the ML-YR region has little increased in the past thirty years but with significantly accumulated SOM and soil nutrient contents. In conclusion, the N and P fertilizers application as well as their runoff losses increased in the last three decades in southern China, but with significant variation among the four investigated regions. Sustainable management practices should be implemented to mitigate N and P non-point source pollution in intensive vegetable production systems.