چكيده لاتين :
Moisture stress, as limited amount and times of irrigation, is effective on crops. In order to study the effect of soil moisture stress at early growth stages on yield and tuber size of four potato cultivars, an experiment was conducted at Rozveh Research Station of Freidan, Isfahan province, in 200land 2002. The experiment design was split-plot with a randomized complete block arrangement and four replications. Main factor included five irrigation treatments (Ij, I2, I3,14 and I5 were the first irrigation after emergence, based on 160, 240, 320, 400 and 160+160 mm evaporation from class A pan, respectively, which were equivalent to 16, 23, 29, 35 and 16+15 days). The next irrigations were performed after depletion of 35-40 percent available moisture in the top 60 cm of the soil profile in all treatments. In I5, the first irrigation was after 160 mm of evaporation from pan and the second irrigation was again after 160 mm of evaporation. Sub-factor included four cultivars: ʹMarfonaʹ, ʹConcordʹ, ʹAgriaʹ and ʹCosimaʹ. The results showed that total yield and large tubers (>55 mm) yield was higher in I2 treatment (33.35 and 19.04 tons ha"1, respectively) than the other irrigation treatments and I5 produced the lowest total and large tubers yield (28.56 and 14.86 tons/ ha"1, respectively). Irrigation treatments didnʹt have any significant effects on medium tubers (35-55 mm) yield, but small tubers (<35 mm) yield in I5 was significantly greater than the other treatments. Number of main stems was not significantly different in irrigation treatments. ʹMarfonaʹ produced the highest total and large tubers yield (36.21 and 22.99 tons ha"1, respectively). Total yield of Concord was significantly greater than ʹAgriaʹ and ʹCosimaʹ and also ʹConcordʹ produced the highest medium and small tubers yield. Large tubers yield of Agria was significantly greater than ʹConcordʹ and ʹCosimaʹ cultivars. Water use efficiency was obtained as 3.54, 3.90, 3.73, 3.74 and 3.28 kg m"3 in Ij to I5 treatments, respectively.
