effects of water deficit on quality of sugar beet at different growth stages

in order to determine the effects of water deficit at different growth stages of sugar beet and optimal usage of water on quality and quantity characters of sugar beet, a factorial experiment based on randomized complete block design was conducted with 13 treatments and four replications in 2000 and 2001 in agricultural research center of hamadan. for the first factor, irrigation withheld in three growth stages consisting of s1,  foliargrowth stage (8-10 leaf stage or about six weeks after planting), s2, root growth stage(after 8-10 leaf stage) and s3, stage of sugar accumulation (near the end of growth stage). the second factor included the number of irrigations withheld at different growth stages of sugar beet from one (i1) to four (i4) times. a control treatment was also included with no water deficit. combined analysis of variance showed that there were significant differences among different growth stages sugar content, juice extraction of sugar and white sugar content. the growth stages were also significantly different with respect to na+, k+, and the amount of molassed sugar. significant differences were also observed among irrigation treatments for all characters except alkalinity. the intraction of growth stages with irrigation treatments was not significant. maximum sugar content and white sugar content at final harvesting averaged over the two years was obtained from s1i1 (withholding irrigation for one time at foliar growing stage) and the minimum amounts obtained from s3i4 (withholding irrigation for four times at the stage of sugar accumulation). withholding irrigation near the end of growth stage decreased sugar content, white sugar content and juice extraction of sugar. in general, water deficit at the end of sugar beet growth stage increased the impurities of root including k+, na+, and consequently decreased juice extraction of sugar and increased the percentage of molassed sugar.