effect of deficit irrigation in the early season on the sugar beet growth indexes

saving in irrigation water is important in the early season of sugar beet. the effect of early season deficit irrigation on the sugar beet growth indexes was investigated in kabotarabad agricultural research station (esfahan) in 1998. the soil texture was silty clay and the experiment design was randomized complete block with 4 relications. six irrigation regimes were applied after. 1) 100 mm (check), 2) 200 mm, 3) 300 mm, 4) 400 mm, 5) 500 mm and 6) 600 mm evaporation from class a pan. the results showed that both leaf area index (lai) and foliage dry matter (dm top) of sugar beet reduced when the length of irrigation intervals were increased. the top growth rate (cgr top) of well watered beet was greater than that subjected to water stress in the early growing season. the cgr top of 100 to 500 mm treatments showed more or less the same pattern, while the 600 mm one exhibited another pattern as compared to the other irrigation treatments. this was probably due to severe of water stress. the cgr top of sugar beet subjected to 600 mm treatment was less than the other treatments. when beet plants were received sufficient water in the early season, their cgr-top reached zero, but the cgr root of these plants were maximum. changes of dm root for all treatments had a sigmoid pattern and by increasing of water stress the dm-root decreased. the reason is probably be due to decrease in carbohydrates transportation from leaves to the storage roots.