Journal Article

A Unifying Concept for the Dependence of Whole-crop N : P Ratio on Biomass: Theory and Experiment

Duncan J. Greenwood, Tatiana V. Karpinets, Kefeng Zhang, Angela Bosh-Serra, Arianna Boldrini and Lyudmila Karawulova

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 6, pages 967-977
Published in print December 2008 | ISSN: 0305-7364
Published online October 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn188
A Unifying Concept for the Dependence of Whole-crop N : P Ratio on Biomass: Theory and Experiment

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Numerous estimates have been made of the concentrations of N and P required for good growth of crop species but they have not been defined by any unifying model. The aim of the present study was to develop such a model for the dependence of the N : P ratio on crop mass, to test its validity and to use it to identify elements of similarity between different crop species and wild plants.

Methods

A model was derived between plant N : P ratio (Rw) and its dry biomass per unit area (W) during growth with near optimum nutrition by considering that plants consist of growth-related tissue and storage-related tissue with N : P ratios Rg and Rs, respectively. Testing and calibration against experimental data on different crop species led to a simple equation between Rw and W which was tested against independent experimental data.

Key Results

The validity of the model and equation was supported by 365 measurements of Rw in 38 field experiments on crops. Rg and Rs remained approximately constant throughout growth, with average values of 11·8 and 5·8 by mass. The model also approximately predicted the relationships between leaf N and P concentrations in 124 advisory estimates on immature tissues and in 385 wild species from published global surveys.

Conclusions

The N : P ratio of the biomass of very different crops, during growth with near optimum levels of nutrients, is defined entirely in terms of crop biomass, an average N : P ratio of the storage/structure-related tissue of the crop and an average N : P ratio of the growth-related tissue. The latter is similar to that found in leaves of many wild plant species, and even micro-organisms and terrestrial and freshwater autotrophs.

Keywords: Biomass; growth rate; model; N : P ratio; plant allometry; plant mass; stoichiometry

Journal Article.  7821 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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