عنوان مقاله [English]
Anethum graveolens L., commonly known as dill, is an annual medicinal plant from the family Apiaceae (Umbelliferae).Water deficit in plants may lead tophysiological disorders, such as a reduction in photosynthesisand transpiration, and in the case ofaromatic crops may cause significant changes in the yield andcomposition of essential oils. These fertilizers have high absorption and maintenance of water and nutrients, high porosity, ventilation and proper drainage in the soil. The role of superabsorbent as a water storage polymer has been proven to reduce the severity of drought stress. The use of zeolite is another way of preventing soil moisture loss. Drought stress reduces the yield of C3 plants due to reduced leaf carbon dioxide and increased respiration. The use of materials such as methanol can partially compensate for the lowering of yield from drought stress. Iran is in a dry and semi-arid region. To evaluate the effect of organic and chemical improver’s application on yield and essential oil percentage of dill (Anethum graveolens L.) under water deficit stress conditions, a field experiment was conducted as split plot in randomized complete block design with three replication in Birjand, Iran, during 2017 growing season. The main factor included three levels of water stress (60, 120, 180 mm evaporation form class A pan) and the sub-factor included five levels of organic and chemical improvers; control (no application), zeolite (5 t. ha-1), vermi compost (6.5 t. ha-1), super absorbent polymer (100 kg. ha-1) and methanol (20 v/v). The results showed that water deficit stress significantly reduced all studied traits except harvest index and essential oil percentage. Also, organic and chemical improvement agents had a positive and significant effect on plant height, number of umbrellas per plant, grain yield, biological yield and essential oil yield. Interaction of water deficit stress and organic and chemical improvement agents was significant on number of umbrellas per plant, number of seeds per umbrella, grain yield, biological yield and essential oil yield. By increasing the intensity of water deficit stress, the use of organic and chemical improver’s increased the yield of seeds and essential oils. In severe stress conditions and in comparison with control treatment, super absorbent application increased the yield of seeds and essential oil to 34.43 and 37.27%, respectively, and methanol spraying increased the yield of seeds and essential oils by 34.17% and 42.85. The results of this experiment showed that the use of organic and chemical improvers reduced the damage to seed yield and essential oil yield in under water deficit stress conditions. Also, the results showed that when the plant is exposed to intense stress, substances such as superabsorbent and methanol can be used to modify the stress. Using these materials under severe stress conditions increased the grain yield by 34% compared to the control. In order to achieve the maximum yield of essential oil, use of organic and chemical improvers has been beneficial. In severe stress conditions, methanol spraying and super absorbent application increased the essential oil yield of dill (Anethum graveolens L.) in Birjand region.