Increasing yield of evening primrose (Oenothera biennis L.) by using chemical and biological fertilizers under drought stress

Introduction Drought is a common problem that seriously affects the quantity and quality of agricultural produce. More than 50% of the world's regions are located in dry and semi-arid regions. Plant growth decreases in drought stress. Water shortages in the world and in Iran have always been a limiting factor for plant cultivation. Drought is a common problem that seriously affects the quantity and quality of agricultural products, such as medicinal plants. The use of agronomic techniques, including soil biological conditions (using mycorrhiza and Azospirilum) and the use of chemical fertilizers, may be effective in reducing the effects of drought stress. Materials and methods In this regard, a field experiment was carried out in two regions of Tehran (semi-arid) and Varamin (arid) in the period of 2014-15. The experiment was split factorial in a completely randomized block design with three replications. The main factor consisted of three treatments without water stress, moderate stress and severe stress (irrigation at 50, 40 and 30 percent of field capacity), and the factorial arrangement consisted of three fertilizer regimes (no fertilizer application, 50 and 100 percent Nitrogen + Phosphorus application requirements for plant), mycorrhizal fungi and Azospirilum bacterium (application and non-application) were considered as a subplot. Drought stress treatments at flowering stage (during flowering until the end of the season) were applied based on soil crop capacity. The following steps were applied to apply water deficit treatments, respectively: First, the field capacity was obtained, first, a plot (length of two meters × two meters wide) from each experimental site completely up to the end of the plain wall of the water filled and was enclosed with plastic (to prevent water evaporation and error) to the soil completely saturated with water. After 48 hours, the water was removed by gravity from the coarse porosity, the plastic was removed from the plots, the soil sample was prepared and, after weighing, in an oven at 105° C for 24 clock was placed. The sample was then calibrated with a precision weighing scale and evaporated moisture content (soil moisture content). Results and discussion The results showed that grain yield and its components (biological yield, 1000 seed weight, number of seeds per plant, number of capsules per plant and number of lateral branches per plant) with irrigation reduction (moderate and severe), were significantly dry weather in the Varamin area decreased. Inoculation of mycorrhiza with combined application of chemical fertilizers and Azospirillum improved seed yield, biological yield, 1000 seed weight, seed number per plant, number of capsules per plant and number of lateral branches per plant under drought stress conditions in arid and semiarid regions. Biological and grain yield in terms of absence of drought stress along with application of chemical and biological fertilizers to the conditions of severe drought stress, with non-application of chemical and biological fertilizers were 60% and 65% respectively for Tehran region and 50% and 59% for Varamin area increased. Reducing the amount of photosynthesis, reducing carbon dioxide absorption, increasing transpiration and decreasing water absorption, increasing leaf temperature due to reduced transpiration and reduced absorption of food can be mentioned due to reduced biological yield and grain yield under drought stress. Conclusions In general, drought stress has reduced the yield and the use of biological fertilizers has caused the plant's resistance to drought stress.