Determination of soil moisture depletion during growth period on quantity of sugar beet root crop

In this investigation the effects of to soil moisture deplation in different stages on some physiological factors such as LAI, R.Y. S.C and Juice Purity were studied. The field experiment was carried out in 1382 in Motahhari experimental station in Kamal-Abad which belongs to the sugar beet seed institute. Two soil moisture deplation (S.M.D) treatments (70 and 90% of available soil moisture content) were imposed at four growth stages (after plant establishment, rapid plant growth stage, maturity stage and maturity to harvesting stage) of plant growth. In addition, a control treatment was added to the factorial combination of two S.M.D. and four-plant growth stage. The field experimental layout were randomized block design in four replication. Results Severe S.M.D at early growth stage reduced the number of root but at other stages had no effects on number of survived roots. S.M.D. at any growth stage reduces foliage weight. However, 40 days after optimizing soil moisture condition the foliage weight is recovered. 20-30 days after optimizing soil moisture condition, moisture content of leaves due to producing fresh leaves increased. This study showed that the first sign of water stress is appeared on leaves condition. Where, 90% S.M.D. cause the old leaves dried and LAI reduced. 70% S.M.D. at non of four growth stages had no effect on root yield. However root yield significantly reduce when 90% of soil moisture was deplated. The mentioned amount of S.M.D. at the last growth stage had no effects on root yield. Results showed that after optimizing soil moisture condition leaves is recovered earlier than root which results the top/ root ratio to be increased. 70% S.M.D. at any of four growth stages had no effect on sugar content. However, sugar content reduced when 90% of soil moisture was deplated at the last plant growth stage. The justification of this kind of observation may be consumption of reserved sugar to produce new leaves. Results showed that with increasing S.M.D at rapid growth stage, impurity (especially Na) content increase. So, in water stress condition, plant tent to accumulate Na and to some less K. Results showed that with increasing S.M.D and plant growth stage, the juice purity is reduced where the molasses increased. 70% S.M.D. at non of four growth stages had no effect on, the juice purity. Increasing the molasses and decreasing juice purity is the direct effects of increasing impurity due to water stress at the latest growth stage. 90% of soil moisture deplation at any stage of plant growth reduced sugar yield and white sugar yield. The main reason was reduction of root yield because of water stress. Results showed that 90% of S.M.D. at 2nd growth stage caused root yield, sugar yield and white sugar yield dramatically to be decreased.