Modelos de crescimento para o feijão-caupi e o milho, sob sistemas de plantio exclusivo e consorciado, no Semiárido brasileiro Fitting growth models for cowpea and maize as sole crop and intercropp in the Brazilian semi-arid

The aim of this work was to evaluate three growth models performance, expolinear, logistic and Gompertz, for accumulated dry matter of cowpea and maize under single and intercropp planting systems in the Brazilian semi-arid. The data used were obtained from two independent field experiments carried out in the same season, with the purpose of calibrating and evaluating these growth models. Statistical (correlation coefficient - r) accuracy indexes (index of agreement - d) and estimative errors (mean error - MBE and square root of mean error - RMSE) were used to analyze the results. The models were fitted using two independent variables: "days after sowing" (DAS) and "accumulated degrees-day" (GDA). The results demonstrated that all models presented good statistical adjustment, r and d values were higher than 0.97 and 0.99 and the maximum values of MBE and RMSE were 1.6040 g m -2 and 1.1102 g m -2 , respectively. The independent variable DAS presented the best fit for all growth models studied. However only, the independent variable DAS limits the application of the models to similar environment conditions observed during the experiment. The biological parameters generated by the expolinear model showed that single cowpea and maize presented morphophysiological development superior to that the cowpea and maize intercropped.