The Virtual Crop-modelling System ‘vica’ Specified for Barley

The paper presents an improved version of the Virtual Canopy model VICA (Wernecke et al. 2000), which is developed to establish a generic functional-structural plant model (FSPM; cf. Vos et al. this volume) specified for barley (Hordeum vulgare L.). The model core is formulated as a set of hierarchically structured objects. These objects are related to morphological and functional ‘plant units’ (organs). The following processes are considered: i) organ initiation, ii) organ growth and senescence, iii) photon transfer, iv) photosynthesis, v) basic features of the carbon (C), and nitrogen (N) metabolism, and vi) mass fluxes between objects. Balance equations are defined for three different substrate classes with their mobile and immobile forms: i) substrates without N, ii) substrates without C, and iii) substrates containing both C and N. This approach leads to a set of coupled nonlinear ordinary differential equations (ODEs) to describe the balance equations of the plant–soil system in terms of the above-defined substrates. On this basis, algorithms can be specified to describe plant architecture as a function of substrate masses and organ age. The extended version of VICA discussed in the present paper is capable to simulate the influence of light and nitrogen supply on the dynamics of architecture and mass. The performance of the model system is demonstrated by simulation studies. A complete parameterization of the model with experimental data is subject to further work.