Effect of different sources of organic and chemical fertilizers on some of physiological parameters of different rice (Oryza sativa L.) cultivars in drought tension conditions

In order to investigate the effect of different sources of organic and chemical fertilizers on some physiological parameters of different rice cultivars in drought tension conditions, an experiment was conducted as split factorial in a randomized complete blocks design with three replications at research farm, located in Sari in 2016. Three levels of tension included drought tension at early tillering stage, drought tension at full heading stage and control (no tension) were considered as the main factor and four fertilizer sources of vermicompost, Azolla compost, humic acid and chemical fertilizer of N.P.K and two cultivars of Shiroudi and Tarom Mahali as factorial as the  sub factor. The results showed that there was a statistically significant difference between Tarom Mahali and Shiroodi cultivars in terms of yield at drought tension levels and different fertilizer sources. The highest paddy yield for Shiroudi and Tarom Mahali cultivars (equals to 6577 and 3776 kilogram per hectare, respectively) was obtained under common irrigation conditions and with the application of tension, the rate of yields decreased, especially with the application of drought tension in the clustering stage, when the yield of Shiroodi and Tarom Mahali cultivars decreased by about 17.6 and 2.9 ercent, respectively. The application of humic acid, Azola compost and vermicompost resulted in 17.3, 13.7 and 8.8 percent increase in grain yield for Shiroudi cultivar and 9.7, 3.8 and 2.6 percent increase in yield for Tarom Mahali under drought tension at tillering stage, respectively, compared to N.P.K chemical fertilizer. The highest amount of total and reducing sugar (147.3 and 4.289 milligram per gram, respectively) was obtained under drought tension conditions at early tillering stage with using the humic acid for Shiroudi cultivar. Therefore, according to the results of the present research, the application of humic acid is suitable for achieving the maximum grain yield of studied rice cultivars under drought tension conditions.