Simulation of the phenology of soybeans

Simulation models of three phases of soybean phenoloyg-sowing to primary leaf, primary leaf to flower initiation and flower initiation to flowering-were generated for the soybean cultivar Lee and others. The basic experimental data were obtained from a series of glasshouse experiments under six temperature regimes in natural light. The data for leaf development rates showed a change in the response to temperature at the first trifoliate leaf stage; this was incorporated into the model. The flower initiation model included parameters for the production and decay of a theoretical flower promoter and for the rate of change of daylength. Time to flower initiation showed at complex relationship to photoperiod which could not be described or approximated to by any simple function. The effects of temperature were marked and showed a strong interaction with photoperiod. The flower development model accounted for a strong temperature response which was conditioned by a photoperiod effect. The three models were combined to form a soybean phenology model which was validated against phenological data obtained from date of sowing experiments conducted under field conditions eng