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Critical nitrogen curve parameters (Lemaire & Gastal 1997 framework)

Source: R/compute_NNI.R
critical_N_curve.Rd

Returns the coefficients a and b of the critical nitrogen dilution curve \(N_c = a \cdot W^{-b}\) (N_c in % DM, W in t DM / ha) for the main Italian arable crops, plus the minimum biomass W_min below which the curve is held constant at \(N_c = a \cdot W_{min}^{-b}\) (standard convention: the curve is only valid for a closed canopy, i.e. W >= ~1-1.55 t DM/ha depending on the crop).

Usage

critical_N_curve(crop)

Arguments

crop

Character. Crop identifier (see list above). Case-insensitive; Italian synonyms ("frumento", "mais", "colza", "riso", "girasole", "sorgo") are accepted.

Value

A list with numeric elements a, b, W_min and reference (character).

Details

Published references:

  • wheat (C3 cereals): a = 5.35, b = 0.44, W_min = 1.55 (Justes et al. 1994)

  • durum wheat: same as wheat (Prey & Schmidhalter 2019)

  • maize (C4): a = 3.40, b = 0.37, W_min = 1.00 (Plenet & Lemaire 2000)

  • rice: a = 5.18, b = 0.52, W_min = 1.00 (Sheehy et al. 1998)

  • rapeseed: a = 4.48, b = 0.25, W_min = 1.55 (Colnenne et al. 1998)

  • grass (ryegrass, fescue, Lolium): a = 4.80, b = 0.32, W_min = 1.00 (Duru et al. 1997)

  • sorghum (C4): a = 3.90, b = 0.39, W_min = 1.00 (van Oosterom et al. 2010)

  • sunflower: a = 4.53, b = 0.42, W_min = 1.00 (Debaeke et al. 2012)

References

Lemaire, G. & Gastal, F. (1997). N uptake and distribution in plant canopies. In: Lemaire G. (ed.) Diagnosis of the Nitrogen Status in Crops. Springer, Berlin.

Justes, E. et al. (1994). Determination of a critical nitrogen dilution curve for winter wheat crops. Ann. Bot. 74, 397-407.

Plenet, D. & Lemaire, G. (2000). Relationships between dynamics of nitrogen uptake and dry matter accumulation in maize crops. Determination of critical N concentration. Plant Soil 216, 65-82.