Environmental factors affecting soybean growth in Manitoba

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Falk, Gary.
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A model to predict daily development of soybeans (Glycine max.) based on environmental factors was developed for Manitoba. By accurately modeling daily development, a date of maturity was predicted. The biometeorological time scale formula (BMTF) (Robertson, 1968) predicts daily development based on maximum and minimum temperatures, and daylength. The time from emergence to physiological maturity of soybeans was divided into three phases in which environmental factors were thought to exert a uniform influence. An iterative regression analysis technique by Robertson (1968) was used to relate development throughout the observed period of a phase at all nine stations years to actual temperature and daylength values on these days. The resulting regression coefficients were then used in the BMTF. The BMTF was able to predict within 2-3 days, the date of maturity using an observed emergence date for the test data. A predicted date of emergence from planting was arrived at by performing regression analysis of daily development (1/days to emergence) on average soil temperature at 20 cm. Predicted emergence dates resulted which were usually within 3 days of the observed date. The model predicting emergence date from soil temperature was incorporated into the BMTF to get a predicted date of maturity from an observed plantlng date. Predicted maturity date was usually within 4-5 days of the observed maturity date...