Adapting a sugar beet simulation model to Mediterranean conditions

Sugar beet grown under Mediterranean climate suffers from sub-optimal environmental conditions, mostly related to temperature and water stress. Such environmental conditions cause both morphological and physiological plant responses, which decrease sucrose content of roots (retrogradation) and ultimately result in lower radiation and water use efficiency. These problems are well known for Mediterranean environments since long time. They are now also becoming visible at more Northern latitudes, having an impact on areas with constantly high sugar beet production potential. The variability of sucrose yield per unit surface has a large impact on the quality of the harvested roots with respect to industrial processing. Potential reasons for seasonal variability of sucrose production could include a variety of factors and are not fully understood. Suitable methodologies for quantification of effects and estimate of impacts are not available. Consequently, no ex-ante analysis can be made to both evaluate environmental constraints to crop performance and optimal management strategies. Simulation models are tools that facilitate such analysis tasks. Generic crop growth simulators implement fixed or simplified carbon partitioning schemes, which are inadequate to estimate the variable source-sink relationships of sugar beet crop subject to environmental stress. Physiologically detailed models hold potential to represent the processes which have an impact on sucrose production in Mediterranean environments, but they are often extremely demanding in terms of parameters and may lack robustness in critical environmental conditions. In this paper we present an approach to adapt a generic simulator to crop-specific response to temperature, varying specific leaf area, dynamic partitioning scheme, and relocation of carbohydrates in the plant, linking the crop tendency to retrogradiation to environmental factors.