Introduction
Maize development is regulated by the effective temperature ($T_{eff}$), which is calculated as the positive difference between the daily mean temperature and a defined base temperature ((par-T1?)) of 6 °C, following Pagès and Pellerin (1994) and Bonhomme et al. (1994).
The development process is divided into five stages, hereafter referred to as XStages, following the HYBRID-Maize framework and the approach of Yang et al. (2016). These XStages represent the key phenological stages of maize development: emergence, tassel initiation, silking, effective grain filling, and maturity (Figure Figure 1).
Development rates between the individual stages are calculated as the ratio between effective temperature ($T_{eff}$) and the corresponding temperature sums (growing degree days, GDD). Specifically, development rates are defined for the phases between sowing and emergence (Eq. 1), emergence and tassel initiation (Eq. 2), tassel initiation and silking (Eq. 3), and silking and grain filling (Eq. 4). The corresponding temperature sums are defined by the parameters (par-GDDemer?), (par-GDDtasini?), (par-GDDS2?), and (par-GDDS3?) (Table ?@tbl-parameters).
Compared to the approach of Yang et al. (2016), an additional temperature sum from emergence to silking ((par-GDDsilk?)) is introduced. This parameter is used to calculate the development rate from grain filling until maturity (Eq. 5). The development rate is derived from the remaining temperature requirement between the total temperature sum to maturity ((par-GDDtotal?)) and the temperature sums of the preceding stages.
All temperature sums are defined as cultivar-specific parameters according to the assumptions of Bignon (1990) for a mid-early maize cultivar grown on soils with medium warming dynamics. The crop is assumed to be harvested at the dough stage, corresponding to the typical harvest time of whole-crop silage maize with a dry matter content of approximately 35 %.
Leaf appearance is simulated following the approaches implemented in HYBRID-Maize and CERES-Maize (Jones and Kiniry (1986); Yang et al. (2016)). The rate of leaf appearance is calculated as the ratio between effective temperature ($T_{eff}$) and the phyllochron parameter ((par-phy?); Eq. 7).
During the early growth period, when the plant has fewer than five leaves (< BBCH15), leaf appearance is assumed to occur at a higher rate. To account for this effect, a reduction factor ($f_{phy}$) is applied to the phyllochron (?@eq-fphy).
In the field trials used for model evaluation, phenological stages were recorded according to the BBCH scale of Lancashire et al. (1991). These observations were subsequently converted into the corresponding XStages for comparison with the model simulations (Figure Figure 1).
DevRate_{S0} = \frac{T_{eff}}{{GDD}_{emer}} \tag{1}
DevRateS0: Development rate between sowing and emergence, Teff: effective temperature, GDDemer: corresponding growing degree days
\mathrm{DevRateS1=}\frac{\mathrm{T}_{\mathrm{eff}}}{{\mathrm{GDD}}_{\mathrm{tasini}}} \tag{2}
DevRateS1: Development rate between emergence and tassel initiation, Teff: effective temperature, GDDtasini: growing degree days from emergence till tassel initiation
\mathrm{DevRateS2=\ }\frac{\mathrm{T}_{\mathrm{eff}}}{{\mathrm{GDD}}_{\mathrm{S2}}} \tag{3}
DevRateS2: Development rate between tassel initiation and silking, Teff: effective temperature, GDDS2: growing degree days from tassel initiation till silking
\mathrm{DevRateS3=}\frac{\mathrm{T}_{\mathrm{eff}}}{{\mathrm{GDD}}_{\mathrm{S3}}} \tag{4}
DevRateS4: Development rate between grain filling and maturity, Teff: effective temperature, GDDtotal: growing degree days from sowing till maturity, GDDemer: growing degree days from sowing till emergence, GDDsilk: growing degree days from emergence till silking, GDDS3: growing degree days from silking till grain filling
\mathrm{DevRateS4=}\frac{\mathrm{T}_{\mathrm{eff}}}{{\mathrm{GDD}}_{\mathrm{total}}\mathrm{-} {\mathrm{GDD}}_{\mathrm{emer}}\mathrm{-} {\mathrm{GDD}}_{\mathrm{silk}}\mathrm{-} {\mathrm{GDD}}_{\mathrm{S3}}} \tag{5}
LeafNo: number of leaves, Teff: effective temperature, phy: phyllochron, fphy: reduction factor for early growth phase.
\frac{{\mathrm{dLeaf}}_{\mathrm{No}}}{\mathrm{dt}}\mathrm{\mathrm{=}}\frac{\mathrm{Teff}}{\mathrm{phy\ *\ }\mathrm{f}_{\mathrm{phy}}} \tag{6}
fphy: reduction factor for early growth phase, LeafNo: number of leaves, constants (0.66, and 0.068) are parameters according to Yang et al. (2016), Jones and Kiniry (1986).
\mathrm{f}_{\mathrm{phy}}\mathrm{\mathrm{=}}0.66+0.068 * LeafNo \quad |\quad LeafNo < 5 \\1 \quad |\quad LeafNo ≥ 5 \tag{7}
Descendence
The class TPenMonteith is derived from TPlantRelatedSubMod, which is derived from TSubmodel which is derived from TObject or TGraphicControl.
TPenMonteith |____TPlantRelatedSubMod |____TSubmodel
State variables
The class TSubDevelopent has 10 following state variable(s).
| CumPH |
[n] |
1 |
number of fully expanded leaves |
| CumPH_Booting |
[n] |
0 |
number of nodes |
| DS |
[-] |
0 |
Development stage for calculating root drymatter (See Hybrid-Maize) |
| GDD6 |
[°C*d] |
0 |
Growing degree days from sowing |
| GDD6_from_emergence |
[°C*d] |
0 |
growing degree days from emergence |
| GDD8 |
[°C*d] |
0 |
Just for Information, not for calculation. |
| TLNO |
[n] |
6 |
TLNO is the total number of leaves that will eventually appear |
| TSum_leafLagphase |
|
0 |
|
| XSTAGE |
[-] |
0 |
Phenological stage, non integer values |
| XSTAGE_till_tassel_emergence |
[-] |
0 |
|
TRUE
Parameters
| GDD6Emergence |
[°C*d] |
68.34 |
Temperature sum sowing to emergence |
| GDD6Silking |
[°C*d] |
822.60 |
Temperature sum silking |
| GDD6Stage2 |
[°C*d] |
510.00 |
Temperature sum tassel initiation till silking |
| GDD6Stage3 |
[°C*d] |
202.60 |
Temperature sum stage 3 |
| GDD6tasini |
[°C*d] |
320.00 |
Temperature sum from emergence till tassel initiation |
| GDD6total |
[°C*d] |
1534.97 |
Temperature sum |
| Phyllochron |
[°C*d] |
54.05 |
Phyllochron |
| Plastochron |
[°C*d] |
29.18 |
Plastochron |
| sen_par |
[-] |
0.15 |
en_fact wird als potenz Funktion angenommen, sen_par ist der Krümmungsfaktor dieser |
| sen_parexp |
[-] |
2.00 |
en_fact wird als potenz Funktion angenommen, sen_parexp ist der Exponent dieser |
| SowingDate |
[-] |
39191.00 |
Date of sowing (days from 1.1.1990) |
| Tbase6 |
[°C] |
6.00 |
Base temperature |
TRUE
| T_{1} |
6 |
°C |
Base temperature for calculating T_{eff} |
Pagès and Pellerin (1994); Bonhomme et al. (1994) |
| GDD_{emer} |
100 |
°C d |
Temperature sum from sowing until emergence |
Bignon (1990) |
| GDD_{tasini} |
320 |
°C d |
Temperature sum from emergence until tassel initiation |
Bignon (1990) |
| GDD_{S2} |
510 |
°C d |
Temperature sum from tassel initiation until silking |
Bignon (1990) |
| GDD_{S3} |
200 |
°C d |
Temperature sum from silking until grain filling |
Bignon (1990) |
| GDD_{silk} |
830 |
°C d |
Temperature sum from emergence until silking |
Bignon (1990) |
| GDD_{total} |
1890 |
°C d |
Temperature sum from sowing until maturity |
Bignon (1990) |
| phy |
50.8 |
°C d leaf⁻¹ |
Phyllochron |
Jones and Kiniry (1986); Yang et al. (2016) |
