نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری دانشگاه تربیت مدرس
2 دکتری دانشگاه تربیت مدرس
3 عضو هیأت علمی دانشگاه ولیعصر رفسنجان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
The incidence of die-back in pistachios (Pistacia vera L.) is common in many pistachio producing countries including U.S., Greece, Italy, and South Africa. This problem also occurs extensively in pistachio orchards of Iran where it has caused yields to be low. In order to evaluate the spread, percent occurrences as well as to determine the causative factor(s) of this incidence, some 203 pistachio orchards located in Rafsanjan, Kerman, Yazd and Khorasan regions were visited during the period from 2002 to 2004. It was noted that from 4 to 90 percent, or on the average 28 percent of the trees, had been affected and that the rate of this incidence had increased by 60% during the ten year period from 1994 to 2004. Soil samples from profile depths of 0-40, 41-80 and 81-120 cm were collected in 31 randomly selected orchards for physicochemical analysis. Likewise, leaf samples as well as samples of irrigation water were collected in those orchards for chemical analysis. Then, correlations between the incidence of die-back and the examined factors were calculated. It was noted that the incidence of die-back in pistachios was positively correlated with soil EC, Na, K, SAR, Na/Ca and Na/K values. A stepwise regression analysis yielded the following equation: Y= 51.799-0.194 (K)soil+0.946 (SAR)soil R2= 0.737 On the basis of our findings and the reports by others that the fungus Paecilomyces variotti was the causative agent for die-back in pistachios, a randomized complete block experiment was conducted with 4 treatments and 6 replications on a total of twenty four 25-year old trees of Fandoghi pistachio variety which were 30% affected by die-back problem to investigate the effect of balanced fertilizer application on preventing this incidence. The treatments included T1= the growers conventional method (ammonium sulfate+triple superphosphate at the rate of 3 kg each per tree); T2=T1+ potassium at the rate of 3kg potassium sulfate per tree; T3= T2+calcium applied as gypsum at the rate of 40 kg/tree; and T4=T3+zinc applied as zinc sulfate at the rate of 1500 g/tree. The direct fungal inoculation of the trees followed two years of the fertilizer treatments. The results showed a significant decrease (at 1% level) in the incidence of die-backs with treatments T2, T3 and T4 as compared with the farmers conventional methods. In other words, the application of potassium,calcium and zinc sulfate reduced this problem by 63 percent.
کلیدواژهها [English]
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