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Abstract. The objective of this research was to investigate the effect of regulated deficit irrigation (RDI) applied at late vegetative stage on yield and water productivity (WP) of Soybean grown in pots. This research was conducted in a plastic house on the Experiment Station of Lampung University from October 2018 to January 2019. Five seeds of soybean (Anjasmoro variety) were sowed in a 10L pot but three plants were removed and only two plants were maintained for further study. Water treatment levels of the RDI were DI1 (100 %) of total available water (TAW) as the control, DI2 (80 %), DI3 (60 %), DI4 (40 %) and DI5 (20 %), arranged in a Completely Randomized Design (CRD) with four replications, totally 20 experimental units (pots) in this research. The water levels were maintained by replacing daily water loss with the same amount of water. After the period of treatment at the late vegetative stage ended, all plants were fully irrigated at field capacity level. The results revealed that the soybean plant started to experience water stress at week IV, and it happened to DI4 and CI5 in that they were significantly different from DI1 (fully irrigated) at p<0.05. Based on DI4 status, critical depletion fraction (p) was concluded to be 0.6, and water stress coefficient (Ks) was 0.79 on the average. Then DI3 was categorized as the optimum option because DI3 did not statistically experience water stress at p<0.05. With DI3 scheme, crop water requirement (CWR) could be significantly reduced from 38875.50 mL (DI1) to 36746.5 mL or 566.08 mm (DI3), while WP and grain yield could be maintained at maximum levels at 0.48 and 8.95 g plant-1 respectively. The WP and grain yield were not significantly different from those of DI1 at p<0.05.