Effect of Drought Stress and Various Fertilizers on Different Aspects of Water Use Efficiency and Biomass of Isabgol

Under arid and semi-arid conditions, water deficiency may limit the use of nitrogen by plant and lead to a decline in crop production and water use efficiency. Therefore, in order to study the effect of drought stress and various fertilizers on different aspects of water use efficiency and biomass of isabgol, a factorial experiment was conducted in a randomized complete blocks design with four replications under microcosm conditions. Treatments included two levels of drought stress (non-stress and with stress) as the first factor, two levels of mycorrhizae (inoculated with G. intraradices and non-inoculated) as the second factor and three fertilizer types (separate application of Azotobacter chrococcum, application of 40 kg N/ha as urea fertilizer, and combined application of azotobacter plus 20 kg N/ha as urea) as the third factor. The results indicated that drought stress reduced the root and shoot biomass on average by 31% and 28%, respectively. But, mycorrhizae caused the increase of root and shoot biomass on average by 65% and 24.7 %, respectively. Water use efficiency increased for the aboveground biomass and total biomass production in drought stress plus mycorrhizae and 40 kg N/ha as urea. However, water use efficiency for seed and mucilage production was only affected by drought stress and mycorrhizae. In conclusion, results showed that water use efficiency for seed production was only increased by mycorrhizal inoculation under drought stress. However, water use efficiency for mucilage production not only increased in drought stress conditions, but also it increased more in mycorrhizal inoculation treatment under drought stress conditions.