A DATA BASE FOR PREDICTING SOYBEAN PHENOLOGY

WANG J., McBLAIN B. A., HESKETH J. D., WOOLLEY J. T. and BERNARD R. L. A data base for predicting soybean phenology. BIOTRONICS 16: 25-38, 1987. The quest for a better soybean phenology model continues, phenological behavior being a necessary part of any crop growth and yield simulation model. New and published data for soybean strains from different maturity groups sown at different dates and locations were analyzed for temperature and photoperiod effects on mainstem node appearance rates and on flowering, early pod fill, and maturity dates. Degree days were calculated from maximum and minimum weather station temperatures using lOoC as the base temperature. When the maximum temperature exceeded 28°C, the difference between it and 28 was subtracted from the 24 h degree day calculation. Photoperiods at floral initiation were estimated as those values that occurred 290 degree days before the first open flower, but those that occurred before the longest day of the year were set to the longest photoperiod for the latitude. Such methods for calculating degree days and photoperiods were arrived at from analyses of the literature and by trial and error. Numerous equations and plots are given for predicting the effects of photoperiod and temperature on soybean phenology of Maturity Groups 000-VII. Such information will be used in soybean management models and in planning further phenological research.