ABSTRACT
Increasing agricultural production by effective use of available water resources or more production per drop is a major challenge during the coming decade. The deficit irrigation is an option that may increase water use efficiency (WCUE). Mahmoodi et al. [22] found that the optimum soil water content is 70% of field capacity for 78.5 tons/ha of root yield of sugar beet. The minimum root yield (52.5 t/ha) was observed at 90% of field capacity. Irrigation at 30, 50 and 70% of field capacity had same effects on sugar content while sugar content was decreased at 90% field capacity. At available soil water content of 70% of field capacity, maximum root yield and better quality were observed. Fabeiro et al. [16] reported that moderate water consumption rate (6898 m3ha-1) was achieved with yields up to 117.64 t.ha-1). Excessive irrigation does not increase yield and maximum WCUE was 7.2 kg.m-3 for nearly 500 mm of water use [21]. Water deficit decreased root yield of sugar beet, but increased the sugar content, amount of potassium and α-amino N amount, and total irrigation depth increased sugar content in sugar beet [2].
