Wheat growth modelling (and other cereals) by inverse thoughts of parsimonious model concepts

The GNR model concept for wheat growth modelling (applicable for all cereals)
Central idea: nitrogen uptake and biomass growth, i.e. (yield) is driven by canopy expansion and canopy prolongation. The canopy is measured as Green Area Index (GAI), taking into account total green biomass instead of the common LAI. Both, canopy expansion and longevity are functions of temperature and precipitation. Additional stresses affect (shortens) canopy longevity and result in yield losses.

Fertilizer supply
Biomass W is partioned into shoot dry matter growth and ear dry matter growth
Finally, ear growth or yield is simplyfied to a linear function of: canopy size and duration, light (PAR) intercepted, N taken up, temperature dependency and shoot biomass translocation. Growth stops with canopy death.
The GNR model includes numerous response functions, which are explained in the report (PDF)

Further explainations:

Switch function concepts
Within the  model  partiones the season of greenish tissue into three phases: I. canopy expansion, II. canopy duration & III. rapid senescence until canopy death. Biomass growth finally stops with canopy death


The model concept offers suitable links for modelling major multiple stresses and more interesting the discrimination of each stress.

Conclusion: The model concept takes into account a complete different perspective on cereals physiology and yield determination.  The way of simplification of complex, time varying, physiological processes is certainly arguable. But it includes a certain fascination by being a complex, but simulatanous regression problem over five compartments and by agreeing with the observations on different scales, seasons and locations with a an accuracy above 95%. In its concept it is contrary to the thinking of all major cereal models, which nowadays are used for yield prediction influenced climate