Predicting growth and yield of winter rapeseed in a Mediterranean environment: Model adaptation at a field scale

The DSSAT Cropping System Model (CSM-CROPGRO) was used to adapt a new model for rapeseed (Brassica napus L. var. oleifera D.C.) and to evaluate it at a field scale under Mediterranean conditions. Model coefficients used to describe growth and development of soybean [Glycine max (L.) Merr.] were chosen as initial reference values. Information on rapeseed from the literature was then used to replace the parameters of the model. Phenology, growth, and partitioning were evaluated using experimental data from two locations of Sardinia (Italy) that were collected in 2007 and 2008. The simulated crop cycle (flowering, first pod, first seed and maturity date), leaf area index (LAI), specific leaf area (SLA), aboveground biomass and pod mass production, yield components, and grain yield and composition (oil and nitrogen content) of rapeseed were compared with specific observations for the early maturity cultivar Kabel, chosen among the most promising under Mediterranean conditions. Base temperatures for processes of this species are typically between 0 and 5 °C for photosynthetic, vegetative, and reproductive processes while corresponding optimum temperatures vary from 21 to 25 °C. Crop cycle was simulated with a RMSE of 0.8 days (d-index = 0.96). Mean predicted aboveground biomass at final harvest was 3825 kg ha-1, with a RMSE of 1582 kg ha-1 (d-index = 0.92). The model estimated SLA with a RMSE of 42.3 cm2 g-1 (d-index = 0.78). Predicted grain yield of rapeseed was 2791 kg ha-1 and was in agreement with the observed data. The results obtained from this model adaptation for rapeseed revealed satisfactory predictions of phenology, growth, and yield of rapeseed and hence suggested that the CSM-CROPGRO model can be used for simulation of rapeseed production in Mediterranean environments although further evaluation for water and nitrogen limiting environments is needed.