عنوان مقاله [English]
Experiments were conducted in 1998 and 1999 to study the effects of different levels of potassium and irrigation intervals on yield and water use efficiency of two genotypes of sugar beet (A37.1 and 12681) in Khorasan Agricultural Research Center (Torogh, Iran). Potassium levels were; no potassium application, increasing potassium to 5% of soil cation exchange capacity (CEC) and second treatment plus plant requirment to potassium. Irrigation interval were 9, 12, 15 and 18 days. In 1998, the amount of water in each irrigation was based on local farmer usage (that is 739 mm). In 1999, for increasing water stress, the amount of water decreased 25% as compared to the previous year. Root yield and white sugar yield in two years and water use efficiency in first year were significantly affected by irrigation amount (P<0.01). Among different irrigation intervals, white sugar yield was the highest in 12 and 9 days irrigation frequencies in 1998 and 1999, respectively. In 1998, root yield, white sugar yield and water use efficiency increased when the potassium of soil increased to 5% CEC in different irrigation intervals. Accordingly, for white sugar yield in 9,12,15 and 18 days irrigation frequencies were 11.5%, 7%, 9% and 10%, respectively. In 1999, applying potassium caused reduction in white sugar yield in 12, 15, and 18 days irrigation intervals, which might be due to the decrease in the amount of irrigation water. However, white sugar yield increased in the 9days irrigation interval. According to the results, potassium application had positive effects on yield and water use efficiency only in normal or moderately water stressed conditions.