Effect of photoperiod, temperature, and solar radiation on soybean growth and yield (a basic approach to the calibration and validation of the soybean crop model: GLYCIM)

This study was conducted on the Plant Science Research Center, Mississippi Agricultural and Forestry Experiment Station (MAFES), Mississippi State University. Nine soybean (Glycine max (L.) Merrill) cultivars were planted on five dates in 1987 and four dates in 1988. These cultivars represented maturity groups IV to VIII and one day-neutral cultivar. The purposes of this study were to validate two versions of the soybean crop model, GLYCIM for vegetative and reproductive growth stages, other plant characteristics, and to determine the effect and impact of photoperiod, temperature, and solar radiation on developmental rates.;Results indicated that both versions predicted the vegetative growth stages with R;The number of main-stem nodes was overpredicted by both versions. Version 2 was used to validate plant height at final harvest and number of pods, and it underestimated them in 74% and 75% of the cases respectively.;Photoperiod was the major environmental factor influencing the developmental rates of flower initiation, floral development, flowering (V1 to R1) and pod-forming periods; temperature played a secondary role. Both influenced the seed-filling period. Solar radiation had no significant effect on these periods for most of the cultivars. It had a significant effect on the flowering period for Braxton and Cobb and on the seed-filling period for Douglas and D82-2740. The seed-filling period of Douglas and D82-2740 seem to be governed by solar radiation as there were no significant effects of photoperiod and temperature on them. It should be possible with these data to develop more mechanistic equations that predict each developmental process and thus enhance the predictability of GLYCIM.