Evaluation of the CROPGRO model for white cabbage production under temperate European climate conditions

The CROPGRO cabbage model, included in the Decision Support System for Agrotechnology Transfer (DSSAT) software, was initially calibrated under tropical Hawaiian climate conditions. Until recently, the application of this model has not been very widespread. Hence, the main objective of this study was to evaluate the CROPGRO cabbage model for white cabbage (Brassica oleracea convar. capitata var. alba L.) production under temperate European climate conditions. Data sets of field experiments from southwest Germany were used for model calibration including observed data of number of leaves, leaf area index, specific leaf area, leaf and stem weight, head weight and total aboveground biomass. For model evaluation, cabbage data sets over three years from southeast and over two years from east Germany were used. The genotype files (cultivar and ecotype), which include the main parameters of crop phenology and plant growth, were adapted to the standard European cabbage cultivar ‘Kalorama’. Observed dry matter cabbage head yields over different years and different locations ranged between 6574kgha−1 and 11926kgha−1; head yields over all datasets were predicted by the model with an accuracy of R2=0.98. Sensitivity analysis conducted under different nitrogen fertilizer amounts (−50% N to +50% N) and two fertilizer application strategies (basal and split) generated logical, useful results from an agronomic point of view. The sensitivity analysis revealed that the efficiency of nitrogen fertilization highly depends on the genetically determined potential yield of a specific cabbage cultivar under given environmental conditions. Overall, the CROPGRO cabbage model proved to be suitable for predicting white cabbage yields under temperate European climate conditions and under different management strategies.