Comparison of different models predicting the date of beginning of flowering in pea (Pisum sativum L.)

In pea, the time of flowering is mainly related to the photoperiod (P) and mean temperature (T-m) during the vegetative period. In field conditions, b oth variables depend mainly on the latitude (LAT) and the date of sowing (R DS). On the basis of these four variables, several empirical models simulat ing the time to flowering either in days or in degree-days were calibrated (the parameters determined) and compared for pea (cv. Solara). Data were fr om trials in various locations throughout France over 8 years and with seve ral sowing dates (from mid-November till mid-April). Surprisingly, the mode l with the more explicative variables (P and T-m) did not give the most rel iable results in held conditions as assessed with a validation sample of si tuations including many years and locations. The best fit and MSEP (mean sq uare error of prediction) were obtained by combining P, RDS and LAT in the model. Models can be constructed to use days or degree-days: models in days are very useful for crop management, whereas models in degree-days are wel l-adapted for crop modelling. The case of autumn sowings was analysed separ ately: models were recalibrated to give a good account of the whole range o f sowing dates. (C) 1999 Elsevier Science B.V. All rights reserved.