Irrigation Frequency and Irrigation Requirement of Three Different Rapeseed Cultivars in Zarghan Area, Fars Province

To investigate the effects of different irrigation levels on yield and oil content of rapeseed, and to determine the irrigation requirement and irrigation scheduling, an experiment with Randomized Complete Block Design consisting of four irrigation treatments replicated 3 times, was conducted in Zarghan Agric. Expt. Station during the years of 2000-2003. The treatments were based on the cumulative evaporation values of 50, 75,100 and 125 mm from class A pan (T50, T75, T100 and T125). The depth of water for each treatment was determined according to the deficit of field capacity and soil moisture content before irrigation. In the three years of experiment, the cultivars: Okapi, Orient and Likord were cultivated and the annual data related to yield and seed oil contents of each cultivar was analyzed separately. In the first year of experiment, the effect of different treatments on yield of Okapi cultivar was not significant, but the maximum and minimum yields were obtained at the T75 and T100 treatments equal to 2678 and 2050 kg ha-1, respectively. The effect of different treatments on seed oil content was significant at the level of 5 %, and the maximum and minimum seed oil contents were obtained at the T100 and T75 treatments equal to 42.50 and 41.66 %, respectively. In the second year of experiment, the effect of different treatments on the yield of Orient cultivar was significant at the level of 5 %, and the maximum and minimum yields were obtained at the T50 and T125 treatments equal to 3133 and 2133 kg ha-1, respectively. The effect of different treatments on seed oil content was significant at the level of 5 %, and the maximum and minimum seed oil contents were obtained at the T75 and T50 treatments equal to 46.38 and 44.82 %, respectively. In the third year of experiment, the effect of different treatments on the yield of Likord cultivar was significant at the level of 5 %, and the maximum and minimum yields were obtained at the T50 and T125 treatments equal to 3667 and 2250 kg ha-1, respectively. The effect of different treatments on seed oil content was significant at the level of 1 %, and the maximum and minimum seed oil contents were obtained at the T50 and T125 treatments equal to 47.63 and 44.60 %, respectively. Also, the best irrigation frequency for the three rapeseed cultivars in the Zarghan area was obtained equal to 10 to 12 days.