Assimilate partitioning

Assimilates being produced in the photosynthesis module are distributed to the single plant organs. The partitioning coefficients are taken from a matrix which includes the development stages of the crop.

Table 1: Matrix of assimilate partitioning for winter wheat

	Root	Leaf	Shoot	Fruit
Sowing to emergence	0.5	0.5	0	0
Emergence to double ridge	0.2	0.2	0.6	0
Double ridge to begin of bloom	0.13	0.2	0.67	0
Bloom	0	0	0.03	0.97
Grain filling	0	0	0	1.0
Senescence	0	0	0	0

The daily partitioning is calculated using linear regression between the elements of the matrix and the relative development:

\[a_i = a_{i,j} + ((a_{i, j+1} - a_{i,j}) \cdot DD_{rels})\]

and

\[DD_{rels} = \frac{DD_{acts}}{DD_{crops}}\]

\(a_i\) Actual assimilate partitioning coefficient for organ \(i\)
\(a_{i,j}\) Partitioning coefficient at begin of stage \(j\)
\(a_{i,j+1}\) Partitioning coefficient at begin of the subsequent stage \(j+1\)
\(DD_{rels}\) Relative phenological development within the stage
\(DD_{acts}\) Actual temperature sum in the developmental stage \([^{\circ}C \, d]\)
\(DD_{crops}\) Plant-specific temperature sum in the developmental stage \([^{\circ}C \, d]\)

The number of organs, developmental stages, as well as their names can be freely defined by the user.

The daily increase of assimilates in the respective organ results from:

\[\frac{d}{dt}W_i = A_g \cdot a_i \cdot dt\]

\(W_i\) Biomass of organ \(i\) \([kg \, TM \, ha^{-1}]\)
\(A_g\) Gross CO₂ assimilation \([kg \, CO_2 \, ha^{-1} \, d^{-1}]\)
\(a_i\) Partitioning coefficient at begin of stage \(j\)
\(t\) Time \([d]\)

The daily mass decrease due to senescence of the single organs is calculated accordingly.