A MODEL FOR PHOTOTHERMAL RESPONSES OF FLOWERING IN RICE .2. MODEL EVALUATION

A detailed nonlinear model, the 3s-Beta model, for photothermal respon ses of flowering in rice (Oryza saliva L.) was evaluated for predictin g rice flowering date in field conditions. This model was compared wit h other three models: a three-plane Linear model and two nonlinear mod els, viz. the modified rice clock model (m-RCM) and a logistic model. Two existing multilocational data sets for photoperiod sensitive and n early insensitive genotypes were used to evaluate the models. For a ph otoperiod-sensitive cultivar, nonlinear models described the data more accurately than the Linear one; the performance of the three nonlinea r models was similar although the logistic model overpredicted days to flowering in a tropical environment. For nearly photoperiod-insensiti ve genotypes, the models were evaluated first using experiments starte d in 1984. The models performed best in the order of the 3s-Beta, m-RC M, logistic, and linear. When the coefficients derived from the 1984 e xperiments were used to predict flowering dates observed in experiment s of 1983, relative performance of the models remained the same althou gh the differences became smaller. The results related to model perfor mance and methods for model parameterization under field conditions we re discussed.