Nitrogen (N) to phosphorus (P) ratio (N:P) has been widely used as a threshold for identifying nutrient limitations in terrestrial plants; however, the associated reliability has not been well assessed.
Relationship between plant N and P content in the unfertilized control plots and type of nutrient limitation determined in the fertilization experiments. Dashed lines depict the N:P mass ratios of 10, 14, 16 and 20. (A) Redrawn from Koerselman and Meuleman (1996), who first proposed the N:P thresholds of 14 and 16; and (B) plotted from the Fertilization Dataset in this study.
Yan et al. synthesized fertilization experiments from 53 publications and 197 records and conducted a random sampling simulation. They found that canonical N:P thresholds had the potential to introduce a large uncertainty when used to detect plant nutrient limitations. These findings suggested that the error risks should be considered carefully in future studies.
Yan, Z., Tian, D., Han, W., Tang, Z., & Fang, J. (2017). An assessment on the uncertainty of the nitrogen to phosphorus ratio as a threshold for nutrient limitation in plants. Annals of Botany, 120(6), 937–942. https://doi.org/10.1093/aob/mcx106