Nitrogen to phosphorus ratio as a threshold for nutrient limitation in plants (Meta-analysis)

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.

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.