SOYBEAN FLOWERING DATE - LINEAR AND LOGISTIC-MODELS BASED ON TEMPERATURE AND PHOTOPERIOD

Temperature and photoperiod are important determinants of the time from emergence to flowering in soybean [Glycine max (L.) Merr.]. A linear and a logistic model have been developed independently for describing the development rate to flowering (a high development rate means a short time to flowering). Field experiments on Arredondo fine sand soil (loamy, siliceous hyperthermic Grossarenic Paleudult) at Gainesville, FL, during 3 yr using a range of sowing dates in each year provided data to evaluate each model. In the first 2 yr, 13 cultivars were grown from 17 sowing dates. The linear model was found to represent adequately these 2 yr of data, but the logistic model was somewhat superior for 12 of the 13 cultivars. The coefficients derived for each model from the first 2 yr of study were used to predict flowering date in the 3rd yr. Both models gave accurate predictions of flowering date, although the larger discrepancies between predictions and observations were obtained with the linear model. Assuming an adequate data base to evaluate the coefficients in each model, either model was able to predict soybean flowering date.