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Highlights • High yield of soybean corresponds to actual evapotranspiration above 380 mm independently of precipitation. • A sum of precipitation and irrigation should be between 350 and 400 mm for high yield. • The I 65 treatment is recommended for soybean cultivation in a temperate climate. • In moderately dry years, irrigation of about 120 mm gives high yields, WP and IWP. • A significant quadratic relation between seed yield and crop ET was observed in non-wet years. Abstract In temperate climatic regions, agricultural production depends on precipitation amount and its distribution during the growing season. A 3-year field study was conducted to investigate the effects of different irrigation regimes on yield parameters and water productivity of sprinkler-irrigated soybean [ Glycine max (L.) Merr.], grown under wet, semi-dry and dry conditions in a temperate environment. Four irrigation levels were applied: full irrigation (I 100 ), 65% and 40% of full irrigation (I 65 and I 40 ) and non-irrigated control (I 0 ). On average, the I 0 treatment resulted in the highest harvest index (HI) and I 100 produced the lowest HI. A significant quadratic correlation between seed yield and crop water use was observed in dry and semi-dry year. The irrigation regime significantly influenced seed yield and water use. I 65 treatment produced the highest seed yield (3.69 t ha–1) and showed the highest water productivity (WP) (0.90 kg m–3) and irrigation WP (1.08 kg m–3). The present study indicated that irrigation is necessary for soybean cultivation in semi-dry and dry years i.e., when seasonal precipitation is lower than about 300 mm. In wet years, with a favourable amount and distribution of precipitation during the growing season, yields are similar to those achieved with irrigation and high ET values of soybean are attributable to increased evaporation. [ABSTRACT FROM AUTHOR]