Wheat Straw Mulching Helps Improve Yield in Sesame (Sesamum indicum L.) Under Drought Stress

Because water resources for irrigation are limited worldwide, it is essential to embrace proper water-saving practices. Field studies were laid out as a factorial split experiment in a randomized complete block design with three replications in 2015 and 2016 to determine the effect of wheat straw mulch (0 and 7.5 tons ha−1) under different irrigation treatments (100%, 80%, 60%, and 40% of the required water) on the physiological characteristics, grain yield, and oil content of sesame (Sesamum indicum L.) genotypes (Borazjan 2, Halil, and Jiroft). Seed yield, 1000-seed weight, seed number, and capsule number were decreased by 64%, 65%, 60%, 70%, and 66%, respectively, as a result of increments in water deficit (from 100 to 40%). However, the application of 7.5 tons ha−1 of mulch mitigated the negative effect of water stress as said factors decreased only by 42%, 40%, 46%, 44%, and 45% as a result of increments in water deficit (from 100 to 40%). Catalase activity (CAT), superoxide dismutase (SOD) activity, proline content, and water use efficiency (WUE) increased with increases in water deficiency, while relative water content (RWC), photosynthetic pigment, and leaf area index (LAI) decreased as water stress rose from 100 to 40%. Applying 7.5 tons ha−1 of straw mulch in 60% available water can be considered a promising management strategy due to both reduction in irrigation water requirements and improvement of low-yield sesame fields in water-deficient areas.