عنوان مقاله [English]
In this study the effects of soil moisture depletion in four different growth stages on some physiological factors such as LAI, R.Y. S.C and WSY were studied. The field experiments were carried out in in Karaj, Mashhad, Esfahan and Miandoab. Two soil moisture depletion (S.M.D) treatments (70 and 90% of available soil moisture content) were imposed at four growth stages. In addition, a control treatment was added to the factorial combination of two S.M.D. and four plant growth stage. Results showed that received water were not significant difference among the treatments. The control, 70 and 90% S.M.D received about 13067, 12607 and 12060 m3/h, respectively. Therefore, difference between treatments basically is because of the times which soil moisture were depleted and to some extend the amount of received water. 70 % S.M.D. at none of four growth stages had no effect on root yield. However, root yield significantly reduces when 90 % of soil moisture was depleted in 2nd and 3rd growth stages. Sugar content reduced when 90 % of soil moisture was depleted at the last plant growth stage. However, 70 % S.M.D. at any of four growth stages had no effect on sugar content. The justification of this kind of observation may be consumption of reserved sugar to produce new leaves. Results showed 90 %S.M.D at rapid growth stage and latest growth stage, caused impurity (especially Na) and molasses to be increased. So, in water stress condition, plant tent to accumulate Na and to some less K. 70% S.M.D. at none of four growth stages had no effect on the juice purity. Results showed that 90 % of S.M.D. at any plant growth stage (especially at 2nd and 3rd growth stages) dramatically reduced sugar yield and white sugar yield. It could be told that 100-120 days after seed planting is the most sensitive growth period (the third growth stage) of sugar beet to water stress. My recommendation is to preserve water it could be irrigation water in early growth stage.