Effects of conventional and optimized water and nitrogen managements on spinach (Spinacia olerocea L.)rrrrrrrrrngrowth and soil mineral N (Nmi.) residues were compared in an open field experiment in which water balancerrrrrrrrrnmethod and N recommendation with the KNS-system were included. It was shown that the conventionalrrrrrrrrrnwater treatment (seasonal irrigated amount: 175 mm) reduced spinach growth compared to the water balancerrrrrrrrrntreatments (seasonal irrigated amount: 80 and 85 mm) at the same N supply level due to N loss throughrrrrrrrrrnleaching caused by excessive water supply. Although 309 kg N ha-1 was applied in the conventional Nrrrrrrrrrntreatment, compared to 82 and 66 kg N ha-l in the optimum N treatments, no significant difference in croprrrrrrrrrnyield was investigated between the N treatments with the same irrigation practice. N uptake in spinach andrrrrrrrrrnsoil residual Nmin contents were also significantly affected by the irrigation practices. The conventional waterrrrrrrrrrnsupply not only decreased water use efficiency, but also resulte Effects of conventional and optimized water and nitrogen managements on spinach (Spinacia olerocea L.) R r r r r r r r r r ngrowth and soil mineral N (Nmi.) Residues were compared in an open field experiment in which water balance r r r r r r r r r nmethod and N recommendation with the KNS-system were included. It was shown that the conventional r r r r r r r r r nwater treatment (seasonal irrigated amount: 175 mm) reduced spinach growth compared to the water balance r r r r r r r r ntreatments (seasonal irrigated amount: 80 and 85 mm) at the same N supply level due to N loss through r r r r r r r r nleaching caused by excessive water supply. kg N ha-1 was applied in the conventional N r r r r r r r r ntreatment, compared to 82 and 66 kg N ha-l in the optimum N treatments, no significant difference in crop r r r r r r r r r nyield was investigated between the N treatments with the same irrigation practice. N uptake in spinach and r r r r r r r r r nsoil residual Nmin c the conventional water r r r r r r r r nsupply not only decreased water use efficiency, but also resulte