THumeWheatPartitioning

1 Summary

GetClassDevNotes("THumeWheatPartitioning",fn_xml_docu)

Module for carbon and nitrogen partitioning at the organ level (root, stem, leaves, grains) in wheat.
       Implements C translocation to grains based on experimental results (see Appendix, Ratjen Diss. 2012).
       N concentrations in organs during vegetative growth are adapted from TSubPartitioningVegNew (U. Böttcher, Meyer-Schatz), with modifications for drought stress according to 2010 experimental results (see Ratjen Diss. Appendix).
       Leaf N distribution is calculated for specific leaf layers at anthesis, based on 2010 experimental results (see Ratjen Diss. Appendix).
       N dynamics are modeled similarly to Bertheloot 2008 (see Ratjen Diss. Appendix).
       Implements sigmoid grain filling (October 2015).
       Partitioning of N deficit follows Ratjen & Kage 2016 (JACS).
       Main authors: A.M. Ratjen, U. Böttcher, D. Neukam, H. Kage et al.
       Restructured and commented by H. Kage, 2024.

2 Lists of model objects

2.1 State variables

The class THumePartitioning has 23 following state variable(s).

State variable	Units	InitialValue	Description
C_Residues	[gC/m2]	0.00	Amount of carbon in crop residues
CropHeight	[m]	0.00	Crop height
DMfineroot	[g.m-2]	0.00	Total fine root dry matter in crop
DMtotal	[g.m-2]	0.00	Total aboveground dry matter in crop
GRNWT_pl	[g/plant]	0.00	Grain dry weight per plant
LFWT_pl	[g/plant]	0.00	Leaf dry weight per plant
N_Residues	[gN/m2]	0.00	Amount of nitrogen in crop residues
NcLeafWinter	[%]	4.51
NcStemWinter	[%]	4.01
NGrain_pl	[g/plant]	0.00	Grain nitrogen amount per plant
NLeaf_pl	[g/plant]	0.00	Leaf nitrogen per plant
NRoot_pl	[g/plant/d]	0.00	Root nitrogen amount per plant
NSen_pl	[g/plant]	0.00	Senescing nitrogen per plant
NShoot_pl	[g/plant]	0.00	Nitrogen per plant
NStem_pl	[g/plant]	0.00	Stem nitrogen per plant
NStoragepool_pl	[g/plant]	0.00	Amount of nitrogen in storage pool per plant
NUptake	[kg/ha]	0.00	N uptake per hectare
potGrainN_pl	[g/Plant]	0.00
RTWT_pl	[g/plant]	0.00	Root dry weight per plant
SEEDRV	[g/plant]	0.00	Seed reserve dry weight per plant
Senwt_pl	[g/plant]	0.00	Senescing dry weight per plant
STMWT_pl	[g]	0.00	Stem dry weight per plant
TempSum	[g/plant]	0.00

TRUE

2.2 Parameters

The class THumePartitioning has 56 following parameter(s).

Parameter	Units	Value	Description
dECDP	[°cd]	2.50000e+02	duration of endosperm cell devision phase
EC_LGend	[-]	4.00000e+01	EC stage at which leaf growth ends
ECcritNcLeaf	[-]	2.70000e+01	BBCH stage from which optimum leaf N concentration starts to decrease with leaf dry matter
fFineRoot0	[-]	6.53000e-01
fFineRootDec	[-]	5.01000e-04
fRootN_ini	[]	4.00000e-01
fRootN_min	[]	1.00000e-01
g	[-]	1.41394e+00	parameter for allometric leaf/stem partitioning
GM4	[-]	1.49153e+02	adjustment of grain number per sqare meter
GM4_2	[-]	2.62330e+00	exponential adjustment of grain number per sqare meter
h	[-]	-1.81303e+00	parameter for allometric leaf/stem partitioning
HarvestDate	[]	1.00000e+06
HImin	[-]	5.10000e-01
Ini_SEEDRV	[g/seed]	5.00000e-02	initial seed weight
iniGRNWT	[mg/grain]	3.50000e+00	initial grain weight (CW 3)
iniLA	[cm2]	5.00000e+00
k_SEEDRV	[-]	1.50000e-01	degradation rate of seed reserves during emergence and early growth
k1	[kg/kg]	1.80000e-03	Michaelis-Menten cons. to mobile N
k2	[J/(m2*s)]	1.00000e+01	Michaelis-Menten cons. to PARi
maxNcStem	[%]	7.00000e+00	maximum N concentration in stem
maxNNI	[-]	1.50000e+00	maximum N nutrition index
maxNupTake	[kgN/ha]	6.00000e+00	parameter to avoid unrealistic high N uptake if maxNupTake is faulty
NcLeafMin	[%]	4.50000e+00
NcLeafVf1	[%*m²/g]	-6.10000e-03	Slope of optimum leaf N concentration per g leaf dry matter
NcLeafVf2	[%DM]	5.95430e+00	Intercept of linear leaf N concentration function under optimum N supply
NcStem_a	[-]	1.47500e-01
NcStem_b	[-]	1.10000e-03
NcStemMin	[%]	4.00000e+00	minimum N concentration in stem
NNIcrit	[-]	1.37700e+00	parameter for leaf stem partitioning under N limitation
NNIinc	[-]	5.95000e-01	parameter for leaf stem partitioning under N limitation
Par_ExtCoeffPAR	[-]	6.75000e-01	Extinction coefficient for PAR (only valid if EvapotranspirationModel uses Option Opt_Exk_Glob = fromPlantModel)
Par_Psi2	[cm]	2.00000e+02	water potential at which water uptake by the plant starts to decrease
Par_rc0	[s.m-1]	5.00000e+01	Canopy resistance at potential transpiration
Par_Weff	[cm]	1.00000e+02	effective rooting depth
pDMTrans	[%]	2.50000e+01
Plants	[plants/m2]	3.20000e+02
pNdefAllo	[-]	6.30000e-01	fraction of N defizit allocated to the stem
psi_crit	[pF]	2.24499e+00	for calculation of kf (allometric leaf/stem partitioning)
psi_s	[1/pF]	2.95694e-01	for calculation of kf (allometric leaf/stem partitioning)
PsiSen1	[pF]	3.60000e+00
PsiSen12	[1/pF]	2.50000e+00
QHI_INC	[-]	1.96000e-01	Slope of regression between QHI and HI for calculation of potHI
QHI_INT	[-]	2.78600e-01	Intercept of regression between QHI and HI for calculation of potHI
relLayerN_Int1	[%]	3.30500e-01
relLayerN_Int2	[%]	2.78300e-01
relLayerN_Int3	[%]	2.29200e-01
relLayerN_S1	[%]	1.04000e-02
relLayerN_S2	[%]	1.70000e-02
relLayerN_S3	[%]	-7.10000e-03
rgr_GrainN	[-]	5.00000e-03
rgr_NcLeafWinter	[-]	2.00000e-02
rgr_NcStemWinter	[-]	2.00000e-02
RND	[1/°cd]	8.00000e-03	rel. rate of phot. N degradation
RNS	[1/°cd]	1.50000e-03	rel. rate of phot. N synthesis
SowingDate	[]	3.86100e+04	Day of sowing
TTfRootN	[]	2.00000e+03	Tsum at which fRootN_min is reached

TRUE

2.3 Variables

The class THumePartitioning has 102 following variable(s).

kable(df.var,  escape = FALSE)

Variable	Units	Description
ActNUptake_m2	[g/m2/d]
actPlantNupTake_m2	[g/m2/d]	actual plant N uptake rate
Assiflow	[g/m2/d]	assimilate flow for DM partitioning
DaysEffGF	[d]	days from BBCH65 unitil LAI=0
DMTrans_pl	[g/plant]
FFINEROOT	[-]	fraction assimilates allocated to fine root growth
fStem	[-]	stem fraction of shoot DM
GlobRadSum	[MJ]	sum of global radiation
GN_NRate	[g/plant]	linear N uptake after endosperm cell division phase
GPP	[grains/plant]	grains per plant
GPPVAR	[grains/plant]	estimation of grains per plant
GPSM	[k/m2]	grains per square meter
GRNWT_m2	[g/m2]	Grain dry weight per m2
GROGRN	[g/(plant*d)]
GROLF	[g/plant/d]	growth rate of leaf dry matter
GROSTM	[g/(plant.d]	growth rate of stem dry matter
GRYD	[dt/ha]	grain yield in dt/ha
HI	[-]	Harvest index
KernelN	[kg/ha]	Nitrogen in kernels
kf_d	[-]	adjustment factor for leaf/stem partioning under drought
kf_n	[-]	adjustment factor for leaf/stem partioning under N limitation
LAIShoot	[m2/m2]	Leaf Area Index of the shoot, excluding ear area index
Leaf_Stem_WT_Ratio	[g/m2]	Ratio of Leaf and Stem dry weight
LFWT_m2	[g/m2]	Leaf dry weight per m2
maxNShoot_m2	[g/m2]	maximum shoot N
Nbal	[g/plant]
Nc_optLeaf	[%]	optimum leaf N concentration
NcGrain	[%]	N concentration in grains
NcLAL__1	[%]
NcLAL__2	[%]
NcLAL__3	[%]
NcLAL__4	[%]
NcLeaf	[%]	N concentration in leaves
NcLeaf_ECLGE		leaf N concentration at the end of leaf growth
Ncmob	[]
NcShoot	[%]	N concentration in shoot
NcStem	[%]	N concentration in stem
NcStem_ECLGE	[g/plant]
NcStraw	[]	N concentration in straw
NcStruc	[%]
Ndef	[g/m2]	N deficiency
NDemand	[kg/ha/d]	Nitrogen demand per hectare
NDemand_pl	[g/(pl*d)]	Nitrogen demand per plant
NGrain_m2	[g/m2]	Nitrogen in grains in g per m2
NHI	[-]	Nitrogen harvest index
NLeaf_m2	[g/m2]	Nitrogen in senescing leaves per m2
NLeaf_Struc1	[g/m2]
NLeaf_Struc2	[g/m2]
NLeaf_Struc3	[g/m2]
NLeaf_Struc4	[g/m2]
NLphot_pl	[g/plant]
NLStruc_pl	[g/plant]
NNI	[-]	Nitrogen Nutrition Index
NNI60	[-]
NoptStem	[%]	optimum stem N concentration
NphLeaf1	[g/m2]
NphLeaf2	[g/m2]
NphLeaf3	[g/m2]
NphLeaf4	[g/m2]
NRoot_m2	[g/m2]	Nitrogen in roots per m2
NSEN_m2	[g/m2]	Nitrogen in senescing plant parts per m2
NShoot_m2	[g/m2]	Nitrogen in shoot per m2
NSP_l	[kgN/ha]	N storage pool leaf
NSP_s	[kgN/ha]
NStem_m2	[g/m2]	Nitrogen in stem per m2
NStemstruc_pl	[g/plant]
NStoragepool_m2	[g/m2]	Nitrogen in storage pool per m2
NTrans_pl	[g/plant]	translocated N per plant
optSLN	[g/m2]	SLN at Ncleaf = Nc_optLeaf
piniGN	[mg/1Kgrains]
PlantNDemand_rate_limited_m2	[g/m2/d]	pot. Plant N demand limited by maxNupTake
potGROGRN	[g/(Plant*day)]
potHI	[-]	potential harvest index
ProtGrain	[%]	Protein content in grains
PTF	[-]
Q45	[-]
QEffGF	[MJ/C�]	Photo-Thermal-Ratio during BBCH65 until LAI=0
QHI	[MJ/�C]
R	[-]	Ratio mobileN /photN
relBF_L1	[]
relBF_L2	[]
relBF_L3	[]
relBF_L4	[]
relTM_L1	[]
relTM_L2	[]
relTM_L3	[]
relTM_L4	[]
RGFILL	[mg/(Plant*day)]
RSWT	[g/m2]	stem reserves during grain filling
SENL	[g/(plant.d]
SENWT_m2	[g/m2]	Senescing dry weight per m2
SLN	[g/m2]	over all specific leaf nitrogen
Stem_Leaf_WT_Ratio	[g/m2]	Ratio of Stem and Leaf dry weight
STMWT_m2	[g/m2]	Stem dry weight per m2
SUMDTTGF	[�Cd]	sum of thermal time since start of grainfilling
sumNLAL	[g/plant]
SWMIN_pl	[g/pl]	minimum stem dry weight per plant, used for translocation calculation and senescence
TKM	[g/kKernel]	Thousand kernel mass
TOPWT_m2	[g/m2]	Shoot dry weight per m2
TOPWT_pl	[g/plant]	Shoot dry weight per plant ((LFWT + STMWT + SEEDRV + GRNWT) )
TSDM_m2	[g/m2]	Total shoot DM per m² (STMWT + LFWT + SENWT + GRNWT + DMTrans)
TSUMEffGF	[C�]

TRUE

2.4 External variables

The class THumePartitioning has 0 following external variable(s).

External variable	Units	Description	Source

TRUE

2.5 Options

The class THumePartitioning has 6 following option(s).

Option	Description
ContOutput	Output every time step?
FinalOutput	Output of final values in separate file?
optDroughtimpact
optNimpact
optRSWT
WithRoots	Option to flag that root growth is calculated within the component

TRUE

2.6 Scientific Background

The partitioning model module of HumeWheat is based mainly based on allometric approaches. The partitioning of dry matter between root, stem and leaf is calculated in two steps: first the root-shoot partitioning is calculated, followed by the leaf-stem partitioning. Both steps are modified under water limited conditions.

2.6.1 Root-Shoot partitioning

According to Kage (2000) the fraction of dry matter allocated to the shoot is calculated assuming linear decrease of the root fraction with temperature sum (TS, base temperature of 0°C) since emergence. If the transpiration is not water limited, the potential plant top fraction ptfp (dimensionless) is calculated as follows:

\begin{align} pt f_p(t) &= \begin{cases} 1-\max\left(0, f_{R0}-f_{Rdec}\cdot TS(t)\right) & \text{if ISTAGE < 5} \\ 1 & \text{if ISTAGE > 5} \end{cases} \end{align} \tag{1}

where ISTAGE<5 is the period before grain filling (Ritchie et al., 1985), fR0 is the initial fraction of dry matter allocated to the root fraction and fRdec is the decrease of this fraction per unit of accumulated temperature. Drought stress not only decreases plant total dry mass, but also changes proportion among root stem, and leaf. Under drought, root:shoot ratio is usually increased, whereas leaf shoot ratio is usually decreased (e.g. Stützel and Liu 2003). According to CERES-WHEAT, the potential plant top fraction is reduced under water limited conditions:

\text{ptf(t)}=pt{{f}_{p}}\text{ - 0}\text{.1}\cdot \text{(1-}{{\text{R}}_{\text{T}}}\text{(t))}. Eq.I.8 The increase of shoot dry matter is therefore:

\frac{d{{W}_{shoot}}}{dt}=\frac{d{{W}_{tot}}}{dt}\cdot ptf(t), Eq.I.9

while the increase in root dry matter is calculated as:

\frac{d{{W}_{root}}}{dt}=\frac{d{{W}_{tot}}}{dt}-\frac{d{{W}_{shoot}}}{dt}. Eq.I.10.

2.6.2 Leaf-Stem partitioning

The development driven concept for leaf-stem partitioning of shoot dry matter used in CERES-WHEAT was replaced by an allometric approach according to Stützel et al. (1988), Stützel and Aufhammer (1991), Kage et Stützel (1999b). The data base for the parameterization of leaf-stem partitioning originates from several field experiments on the experimental farm Hohenschulen and includes destructive measurements of several cultivars (Meyer-Schatz et al., in preparation). The fraction of stem growth fstem (dimensionless) on shoot growth is thereby expressed as a function of leaf dry matter Wleaf [g.m-2], with two allometric fit parameters (g, h).

\frac{d{{W}_{L}}}{dt}=\frac{d{{W}_{V}}}{dt}\frac{1}{1+{{e}^{h}}W_{L}^{g-1}g} \tag{2}

2.6.2.1 Modified Leaf-Stem partitioning due to water limited conditions

For considering the drought induced decrease in leaf mass accumulation a correction factor kf (dimensionless) was added to the allometric equation:

{{\text{f}}_{\text{stem}}}\text{(t)=min(1,1-}\frac{1}{\text{(1}+{{\text{e}}^{\text{h}}}\cdot \text{g}\cdot {{\text{W}}_{\text{L}}}{{\text{(t)}}^{\text{g-1}}}\text{)}}\cdot kf\text{(t))} \tag{3} The minimum value of kf is one, but increases linearly if pFroot Eq.I.6) exceeds the threshold value pFcrit. Thereby, kfinc describes the slope of the increase, proportional to the difference between pFroot and pFcrit:

\text{kf(t)=max(1,1}+\text{(p}{{\text{F}}_{\text{root}}}\text{(t)-p}{{\text{F}}_{\text{crit}}}\text{)}\cdot \text{k}{{\text{f}}_{\text{inc}}}) \tag{4}

The Rain out shelter experiment 2010 (Exp.I.6) was used for the parameterization of the concept using measured water contents and destructive shoot, leaf and stem dry mass. The calibration contained measurements between 27.04. and 27.05.2010. The measured dry matter accumulation between two sample dates was linear interpolated against thermal time. The daily pFroot Eq.I.6 values, linearly interpolated between measurements, were related from measured water contents and simulated vertical root distribution. Starting with measured stem dry matter for each plot the allometric parameters (g,h) were optimized by minimizing the RMSE between estimated and measured stem dry mass without consideration of the kf correction. As a second step the pFcrit and kfinc were calibrated considering pFroot by minimizing the RMSE between estimated and measured stem dry mass. The daily increase of stem dry matter Wstem [g.m-2] is calculated as a function of fstem and increase in shoot dry matter:

\frac{\text{d}{{\text{W}}_{\text{stem}}}}{\text{dt}}\text{=}\frac{\text{d}{{\text{W}}_{\text{shoot}}}}{\text{dt}}\cdot {{f}_{stem}}(t), {#eq-dWstemdt}

where the increase of leaf dry matter Wleaf [g.m-2] is the difference between shoot and stem dry matter accumulation:

\frac{\text{d}{{\text{W}}_{leaf}}}{\text{dt}}\text{=}\frac{\text{d}{{\text{W}}_{\text{shoot}}}}{\text{dt}}\text{-}\frac{\text{d}{{\text{W}}_{\text{stem}}}}{\text{dt}} \tag{5}