Dynamic phenological model for winter rye and winter barley

A detailed dynamic crop stand phenological model is presented for winter barley and winter rye. The modelled phenological stages are described in different scale units (FEEKES [1-20], BBCH [1-100] and DC [1-100]) and a differentiation in mathematical approaches and in parameterisation is made between the germination, the vegetative and the generative phases. The following driving forces are taken into account: temperature, day length, drought stress and nitrogen availability. Drought stress is described using the ratio of actual to potential evapotranspiration and nitrogen availability is described using the nitrogen content in the above-ground biomass. Vernalisation is considered as a process influencing phenology and is described normalised between 0 and 1. In the paper the model parameters are listed separately for winter barley and winter rye. Model parameterisation and validation results are presented for three different German locations (Müncheberg, Hohenfinow, Halle). The comparison of calculated and observed phenological phases (emergence, shooting, flowering, maturity) gives an R2 between 0.87 and 0.99 for winter rye and between 0.92 and 0.99 for winter barley. For these phenological stages the maximum mean deviation between calculations and observations is 5 days. For tillering an insufficient agreement was occurred only. Investigations regarding the geographical extrapolation of the model are carried out for two different German locations (Dedelow and Mariensee). The model-experiment-comparison results for all phenological phases show a sufficient accuracy (R2 = 0.98, N = 82), followed by the presentation and discussion of their results. Model simulation runs with drought stress and not enough nitrogen availability show the dominance of drought stress induced phenology acceleration.