ArableDNDC

Table of Contents

• User guide
  • Model structure
  • Parametrization
• Transpiration
• Roots
• Crop development
• Nitrogen demand and crop growth
• Nitrogen Uptake

User guide

The crop growth model ArableDNDC originates from the DNDC Model ([47]). ArableDNDC simulates the carbon and nitrogen cycle of crops. Processes are described in a universal way and plants are primarily distinguished by species-specific parameters that can be accessed and calibrated externally. Dynamics of plant carbon (C) and nitrogen (N) are primarily calculated based on temperature driven crop development and associated N demand and N uptake/fixation.

Model structure

ArableDNDC can be either run in subdaily or daily time resolution.

Parametrization

The following lists includes species parameters that might be calibrated in order to represent a specific plant. See the description of respective sections for more details on parameter behaviour.

Nitrogen related parameters:

• nc_fruit_max (optimum nitrogen content of the fruit)
• nc_fruit_min (minimum nitrogen content of the fruit)
• nc_fineroots_max (optimum nitrogen content of fine roots)
• nc_fineroots_min (minimum nitrogen content of fine roots)
• nc_structural_tissue_max (optimum nitrogen content of structural tissue)
• nc_structural_tissue_min (minimum nitrogen content of structural tissue)
• nc_foliage_max (optimum nitrogen content of foliage)
• nc_foliage_min (minimum nitrogen content of foliage)

Allocation related parameters:

• fraction_root (root fraction of total biomass at maturity)
• fraction_fruit (fruit fraction of total biomass at maturity)
• fraction_foliage (foliage fraction of total biomass at maturity)

Plant development related parameters:

• gdd_base_temperature
• gdd_max_temperature
• gdd_maturity
• gdd_grain_filling
• gdd_flowering

Drought

• h2oref_a (determines drought resistance)

Nitrogen uptake

• tlimit (minimum temperature required for nitrogen uptake)
• k_mm_nitrogen_uptake (root affinity to soil nitrogen)

Nitrogen fixation

• ini_n_fix (fraction of total nitrogen that might be fixed)

Respiration

• maintenance_temp_ref (reference temperature for maintenance respiration)
• mc_root (maintenance respiration coefficient for roots)

Root exsudation

• doc_resp_ratio (ratio of doc exsudation in relation to root respiration)

Senescence

• senescence_drought (coefficient of senescence related to drought)
• senescence_frost (coefficient of senescence related to frost)
• senescence_age (coefficient of senescence related to age)

Fineroots turnover

• tofrtbas

water demand

• wuecmax (water use efficiency)

Structure

• exp_root_distribution (coefficient for exponential root distribution)
• height_max (maximum plant height)

Transpiration

Calculates potential transpiration on
a) water use efficiency and carbon uptake: potential_crop_transpiration()

Roots

Roots are described by the rooting depth, which grows linearly with GZRTZ (default 1cm/day) up to a maximum value ZRTMC (default 1m) (see Fine root distribution).The distribution of fine roots follows a sigmoid function (see Sigmoid root distribution).

Crop development

Crop development is determined by growing degree days \(GDD\):

\[ DVS = \frac{GDD}{GDD_{max}} \]

Vernalization

Growing degree days are only upgraded for:

\begin{eqnarray*} T &\overset{!}{>}& max \left(0, \Psi_{TLIMIT} \right) \\ GDD &\overset{!}{<}& \Psi_{GDD\_MATURITY} \end{eqnarray*}

Nitrogen demand and crop growth

Carbon assimilation on biomass growth are calculated depending on nitrogen demand and uptake.

Nitrogen Uptake

Crops are able to take up \(NO_3^-\) and \(NH_4^+\).