Correction to: Allometric approach to crop nutrition and implications for crop diagnosis and phenotyping. A review
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Correction to: Agronomy for Sustainable Development
Due to a different interpretation of a query about figure numbering during proof stage, figures and captions in above mentioned article got mixed-up in the final version. The publisher and typesetter regret this occurrence and apologize for the inconvenience caused.
Consequences for assessing N use efficiency by crops
Derivative of Eq. (7) with time allows the expression of the rate of crop N uptake (dNupt/dt) in relation with the crop growth rate (dWsh/dt) and the shoot mass (Wsh):
dNupt/dt = abWshb-1 × dWsh/dt Eq. (7′)
Under non-limiting N supply, the crop N uptake rate (dNupt/dt) depends on the potential crop mass accumulation rate (dWsh/dt), but it declines as crop mass increases. Devienne-Barret et al. (2000) showed that the rate of crop N uptake is dependent on both crop growth rate and soil N availability leading to a family of Nupt-Wsh trajectories for each steady state condition of soil N supply as represented in Fig. 4. This dual dependency of N uptake is well explained by physiological evidence on feed-back regulation of root absorption capacity of mineral N (nitrate and ammonium) by shoot growth through C and N signals (Gastal and Saugier 1989; Lejay et al. 1999).
If Nf represents the rate of N fertilizer application, the Nitrogen Use Efficiency (NUE = dWsh/dNf) for crop mass production is a function of two components: (i) the N Absorption Efficiency (NAE = dNupt/dNf) and (ii) the N Conversion Efficiency (NCE = dWsh/dNupt), so that:
NUE = NAE × NCE (8)
dNf being the increment in N fertilization rate. Then the Nupt-Wsh allometry has two important consequences for analyzing variations in NUE due to genotype-environment-management interactions as underlined by Sadras and Lemaire (2014):
(i)NAE is partly determined by crop growth rate so that genotypes having a higher crop mass should have a higher NAE than slow growing genotypes. This effect is shown on Fig. 4 where any increment in Wsh is associated with a corresponding increment of Nupt for each N supply. So genotypic variation in NAE has to be compared at a similar shoot mass otherwise the difference would be trivial.
(ii)The N dilution process implies that dNupt/dWsh decreases as shoot mass increases, so that NCE (dWsh/dNupt) increases as shoot mass increases. Consequently, the NCE of different genotypes has also to be compared at a similar shoot mass otherwise the difference observed would be obvious with a larger crop having always a higher NCE than a smaller one.