The effects of deficit irrigation practices on evapotranspiration, yield and quality characteristics of two sesame varieties (Sesamum indicum L.) grown in lysimeters under the Mediterranean climate conditions

In this study, we investigated the effects of deficit drip irrigation practices on evapotranspiration, water-yield relations, and quality characteristics of two sesame varieties (Muganli-57 and Birkan) grown in the lysimeters under the Mediterranean climate conditions. Irrigation treatments were rainfed (non-irrigated) (I₀), drip irrigation with 25% (DI₂₅), 50% (DI₅₀), 75% (DI₇₅), and 100% (DI₁₀₀) of cumulative evaporation (Epan) measured in Class A pan with three replications. The applied water was corrected by the percentage of vegetation cover until the full cover was attained. Evapotranspiration of Muganli-57 and Birkan ranged from 157.8 to 518.8 mm and 156.4 to 509.2 mm, on average, respectively. The yield values changed between 0.46 and 2.06 t ha⁻¹ in Muganli-57 and between 0.35 and 1.95 t ha⁻¹ in Birkan. Based on the 2-year results, water use efficiency (WUE) of Muganli-57 variety (3.5 kg ha⁻¹ mm⁻¹) was numerically higher than that of the Birkan variety (3.4 kg ha⁻¹ mm⁻¹). In both varieties, it was determined that deficit irrigation generally reduced the yield. However, WUE did not decrease monotonically with decreasing irrigation level. DI₅₀ treatment maximized WUE for two varieties in both years while DI₇₅ maximized WUE for Muganli-57 in 2014. Although irrigation-variety interaction affected relative water content, chlorophyll content index, and seed dry matter, their effect tended to be weak and inconsistent between the 2 years of the study. Deficit irrigation decreased the oil content of sesame and increased its protein content. Similarly, deficit irrigation treatments decreased the linoleic acid content and increased oleic acid content in 1 year but not the other. It was concluded that the Birkan variety is more suitable for irrigated conditions due to the growth characteristics and less saturated fatty acid content. On the contrary, Muganli-57 variety is suitable for non-irrigated conditions in terms of water economy and fatty acid composition.