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ARS Home » Research » Publications at this Location » Publication #61908
Title: SEPARATING PHOTOPERIOD AND TEMPERATURE EFFECTS ON THE DEGREE DAY REQUIREMENT FOR FLORAL EVENTS IN SOYBEAN

Author
item ZHANG, L - UNIV OF ILLINOIS, URBANA
item WANG, R - UNIV OF ILLINOIS, URBANA
item Hesketh, John

Submitted to: Biotronics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Maximum and minimum daily temperatures from weather stations are used to calculate degree days as they accumulate over the growing season. Such degree day estimates along with equations for effects of daylength on flowering are used in computer models to predict flowering, early pod fill and maturity in soybean. Over the years there has been evidence that the degree day-daylength effects on flowering date were much more complicated than this. From a date-of- planting study involving many strains of soybean we were able to separate out a degree day-temperature effect (the higher the temperature, the more degree days required before a flower) as well as a daylength effect, both of which had not been accounted for earlier. This new information is being used in a new model at Urbana for predicting soybean growth and yield. Such models offer great potential for making management decisions during the growing season.

Technical Abstract: A date-of-planting study of time from emergence (VE) to floral bud initiation (R0, detection of floral bud primordium) and first flower (R1) was carried out at Urbana IL USA for soybean genotypes representing maturity groups (MG) 00 through VIII. Growing degree days, based 10oC with a cutoff at 30oC, were calculated for VE-R0-R1 and VE-R1 and VE-R1 and were plotted against the average photoperiod between events. We found a temperature relationship among GDD values between events for MG's00-I; subtracting these GDD values from those of MG II or greater and plotting the residual or adjusted GDD (AGDD) values (or 1/AGDD values) vs. average photoperiod improved the linear or curvilinear relationship involved. Photoperiod effects on R0-R1 were significant for later-maturing genotypes (MG IV+or greater) as reported earlier. These phenology-temperature-photoperiod relationships greatly improved our ability to predict phenology with computers for real world situations.