Environmental Effects of Nitrogen, Phosphorus, and Potassium Fertilization in Agriculture: A Bibliometric Analysis and Literature Review

Agriculture underpins global food security; yet, inefficient or excessive nitrogen (N), phosphorus (P), and potassium (K) fertilization can generate interconnected environmental pressures. Direct environmental effects are much more extensively documented for N and P than for K, which is more often examined through nutrient imbalance, soil–plant interactions, and its interactions with N and P. This study combines a bibliometric analysis of 3649 articles and reviews indexed in the Web of Science Core Collection (SCIE and SSCI) from 1991 to 2024 with a literature review. The objective is to map the evolution, knowledge structure, and emerging frontiers of research on the environmental effects of agricultural NPK fertilization and to identify the knowledge gaps and priorities for sustainable nutrient management. The analysis shows a sustained growth in publication output, increasing interdisciplinarity, and major research hotspots involving nutrient cycling, environmental impacts, sustainability, and nutrient-management technologies. The synthesis further identifies persistent gaps in integrated N–P–K interactions, the long-term evaluation of precision nutrient management, compound climate-related risks, and the links between scientific evidence and governance. Based on these findings, we develop an integrated NPK environmental-management framework connecting fertilizer inputs, nutrient interactions, soil processes, environmental outcomes, management interventions, and policy support. The combined bibliometric and literature-review approach therefore moves beyond mapping the field to provide a structured basis for future research and more integrated nutrient-management strategies.