The responses of ecophysiological processes such as leaf expansion and plant transpiration to soil water deficit have been reported to be genotype-dependent. To study such responses in soybean, a two-year (2017 and 2021) outdoor pot experiment was carried out on the Heliaphen automated phenotyping platform at INRAE in Toulouse (France). Six varieties (Sultana-000, ES Pallador-I, Isidor-I, Santana-I/II, Blancas-II, and Ecudor-II) belonging to four maturity groups were subjected to progressive water deficit from the reproductive stage R1 for 17 and 15 days in 2017 and 2021, respectively. The fraction of transpirable soil water (FTSW) was used as an indicator of soil water deficit. Non-linear regression was used to calculate FTSWt, i.e., the FTSW threshold for which the rate of the ecophysiological process in stressed plants starts to diverge from a reference value. Among six varieties, regarding leaf expansion, cv. Santana was more tolerant (FTSWt = 0.36 in 2017, FTSWt = 0.48 in 2021) to soil drying while cv. Isidor (FTSWt = 0.69 in 2017, FTSWt = 0.71 in 2021) and cv. ES Pallador (FTSWt = 0.69 in 2017, FTSWt = 0.70 in 2021) were the most sensitive. However, there was no such difference between their transpiration responses (for Santana, FTWSt = 0.22 in 2017, FTSWt = 0.30 in 2021; for Isidor, FTSWt = 0.42 in 2017, FTSWt = 0.33 in 2021; for ES Pallador, FTSWt = 0.30 in both 2017 and 2021 experiments). Such a non-destructive phenotyping method could bring new information to variety testing process and provide paths for integrating genotypic variability into crop growth models used for simulating soybean responses to water deficit at a plant, field, or regional level.