determination of yield response factor (ky) of sugar beet to deficit irrigation at different growth stages

this study was conducted to determine the yield response factor (ky) of sugar beet to deficit irrigation at different growth stages. a field experiment was conducted in sharekord agricultural research station over two growing crop seasons (1996 -1997) using a randomized complete block design with three replications. plots were assigned to five levels of deficit irrigation treatments: e0 (full irrigation), e1 (85%), e2 (70%), e3 (55%) and e4 (30%) of actual evapotranspiration of sugar beet plant at three growth stages t1: leaf growth stage, t2: tuber growth stage and t3: sugar accumulation growth stage. reference crop evapotranspiration and potential evapotranspiration of sugar beet was determined by drainage lysimeter using neutronmeter. after maturity, root yield, yield components and yield response factor were measured. results showed that yield was highest (49.500 t/ha) in e0 (full irrigation) and lowest (24.6 t/ha) in e4t2. actual evapotranspiration of sugar beet was 884mm. the values of yield response factor (ky) were 0.34- 1.38 at the first stage, 0.34- 1.33 at the second stage and 0.34- 1.39  at the third stage and the lowest evapotranspiration (625 mm) was obtained in e4t2.