SSM-Wheat is a model to simulate wheat crop phenology, growth and yield formation. The model was derived from the general (wheat) model described by Soltani and Sinclair (2012). The differences between these two models are:

*   Yield formation is simulated as described for SSM-chickpea. That is, yield formation is simulated based on linear increase in harvest index, but daily seed growth rate is limited to current crop photosynthesis plus daily rate of mobilized dry matter from vegetative organs. Slope of linear increase in harvest index is adjusted for pre-seed growth conditions experienced by the crop. Crop mass at beginning seed growth is used as an indicator of the conditions. For more information please refer to Soltani and Sinclair (2011).

* Daily increase in rooting depth with unit of mm per day was replaced with mm per oC (1-2 mm per oC), so daily increase in rooting depth is obtained by multiplying this rate and daily temperature unit. This modification better fits winter and spring-sown crops.

* A vernalization saturation days (VDST; Number of vernalization days which saturates vernalization response) of 50 days is used for all cultivars. Thus, cultivars difference is accounted for by VSEN, i.e. vernalization sensitivity coefficient.

* A modified beta function instead of a dent-like function is used to describe response of phenological development rate to temperature. A quadratic function is used to describe response of phenological development to photoperiod as in SSM-chickpea (Soltani and Sinclair, 2011).

* Various phenophases like days to tillering, stem elongation and so on are simulated.

* The killing effect of frost (freezing temperature) on LAI is simulated.

* The effect of flooding is simulated.

* A multilayer soil submodel is used. Soil water factor for calculation of run-off is obtained from soil water content in top layers 1 & 2.

* Nitrogen application can be simulated based on days after sowing (DAP) or cumulative biological days since sowing (CBD).

* Irrigation applications can be simulated based days after sowing (DAP) or cumulative biological days since sowing (CBD) or day of year (DOY). An automatic irrigation management is available, too.

References:

Soltani, A., Sinclair, T.R., 2011. A simple model for chickpea development, growth and yield.   Field Crop Res. 124, 252-260.

Soltani, A., Sinclair, T.R., 2012. Modeling Physiology of Crop Development, Growth and Yield. CAB International, Wallingford, UK.

Sotani, A., Maddah, V., Sinclair, T.R., 2013. SSM-wheat: a simulation model for wheat development, growth and yield. Int. J. Plant Prod. 7: 711-740. (Open Access)