Effects of drought stress and different types of organic fertilizers on the yield and yield components of safflower (Carthamus tinctorius L.)

Management of organic fertilizers in terms of environmental impact and crop yield is important، especially in arid and semiarid regions. The objectives of this work were to evaluate the effect of drought stress and organic fertilizer on some morphological and yield components of safflower. The experiment was conducted as a split-plot based on a randumaized complet block design with three drought stresses: irrigation at 35، 55 and 75% of ready available water (RAW) depletion comprising the main-plot، and four fertilization systems: non-application (control)، application of 40 tons of compost ha-1، humic acid spraying (1. 5 g per litr) and combining compost and humic acid as sub-plot that were applied with three replications. The experiment was conducted in 2013 at the Zabol University research farm in Zabol، south Iran. Drought stress reduced oil yield، chlorophyll fluorescence and membrane stability. Delays in irrigation by 75% RAW depletion reduced oil yield by 68. 6% compared with the control. Organic fertilizer application increased oil content and oil yield، membrane stability، carbohydrates، peroxidase، catalase and guaiacol peroxidase activiteis. Integrated application of compost and humic acid increased oil yield by 99. 7% over the control. Application of humic acid and compost can be combined to develop safflower cultivation in Sistan، especially in mild stress conditions.