the effect of soil water depletion at different growth stages of sugar beet seed-bearing plants on seed growth trends, yield and quality

this study was carried out in order to identify the effects of soil water depletion (swd) on monogerm sugar beet (cv. shirin) seed growth trend at different growth stages. an experiment was conducted in randomized complete block design (rcbd) with three replications in ardebil agricultural research station. during 2002 and 2003 cropping seasons, nine treatments including control (irrigation after 50% swd), irrigation after 70 and 90% swd in bolting, early flowering, peak of flowering and seed growth stages were compared. treatments of irrigation after 70 and 90% swd led to the saving of water use by 1.8 and 18.3%, respectively compared with the control (3167 m3/ha). according to the results, swd at different growth stages had no significant effect on crude, marketable and standard viable seed yield compared to the control treatment. however, the highest water productivity was obtained after eliminating one of the irrigation intervals, particularly at peak of flowering stage  which based on crude (1166 kg/ha), marketable (917 kg/ha) and standard viable (250 kg/ha) seed yield equates 0.450, 0.354 and 0.096 kg sugar beet seed/m3 of water use, respectively. stress during seed growth period led to an increase in standard seed portion, which was due to an decrease in oversize seed portion. the depletion of 90% swd at early and peak of flowering stages increased chaffy seed percentage from 7.55% (control) to 9.35 and 9.34%, respectively. the highest germination rate was obtained at early flowering stage (81.88%) in control and 90% swd at early flowering stage, but stress at other growth stages of sugar beet seed-bearing plants decreased seed germination rate. on the other hand, stress at peak of flowering stage increased seed growth rate by 0.0534 mg/day, and irrigation after 70% swd at early flowering stage had the highest effective grain filling period (38.73 days). the highest seed weight was obtained about 35 days after 50% flowering (1.971 mg/seed) in the treatment of the irrigation after 70% swd, being 0.195 mg/seed heavier than the weight of seeds from control treatment.