the effect of irrigation in spring on water use efficiency and yield of autumn sown sugar beet

to study the effect of variable irrigation in spring on water use efficiency, quantity and quality of root and sugar yield of two sugar beet cultivars shirin and rasolan, an experiment was conducted at safiabad agriculctura research center during 2003-04 and 2004-05 cropping seasons. the experiment was designed in  a split plot with four replications in which five water supply treatments 25, 50, 75,100 and 125 percent of the plant water requirment (pwr) as drip irrigation were in main plots and two sugar beet cultivars in subplots. there was a significant difference between years for most of the sugar beet yield parameters, whereas differences among water supply treatments were significant only for root yield, α-n, alkalinity, and irrigation water use efficiency (iwue) of root and sugar yield. increasing of water volume increased root yield and alkalinity and decreased iwue for sugar and root yield. the 100 and 25% pwr treatments had the highest (84t/ha) and the lowest (76t/ha) root yield, respectively. the 25% pwr treatment had the highest iwue for root and sugar yield which were 18.7 and 2.6 kg/m3, respectively. there was no significant difference between cultivars for any of yield parameters. increment of water supply increased leaf area, leaf number and fresh dead leaves (leaf+petiole) and reduced root/shoot ratio, and dry matter of leaf and root. based on the results of this experiment, the 25% pwr as drip irrigation in spring, can be recommended for autumn sugar beet in dezful region.