Determination of yield and water use productivity of sesame irrigated with subsurface drip irrigation under different water deficit conditions

This study investigates the effects of subsurface drip irrigation (SDI) at varying lateral depths (D1: 20 cm, D2: 30 cm, and D3: 40 cm) on evapotranspiration, water use productivity (WUP), and plant water stress index of the Muganlı-57 sesame variety. The experiments were conducted under different irrigation regimes: S1 (full irrigation without water stress), S2 (mild water stress), S3 (moderate water stress), and S4 (severe water stress). The research was conducted in 2019 and 2020 in a clay loam soil under Mediterranean climate conditions, with irrigation water quantities adjusted according to the percentage of plant cover. The average evapotranspiration values recorded for D1 at S1, S2, S3, and S4 were 338.5, 241, 143.5, and 14 mm, respectively; for D2 the values were 263, 188.5, 113.5, and 14 mm; and for D3, they were 257, 184, 111, and 14 mm. In the first year, the highest water use productivity (WUP) was recorded at D3 for S2 (8.4 kg ha⁻¹ mm⁻¹), and in the second year, the highest WUP was again at D3 for S2, measuring 9.0 kg ha⁻¹ mm⁻¹. Over both years, the WUP for S2 at D3 was significantly higher. In contrast, the lowest WUP values were obtained from D1 at S1, with values of 4.2 and 4.6 kg ha⁻¹ mm⁻¹ in the respective years. The highest irrigation water use productivity (IWUP) was achieved at D3 for S2, yielding 12.5 kg ha⁻¹ mm⁻¹ in the first year and 13.1 kg ha⁻¹ mm⁻¹ in the second year. Coversely, the lowest IWUP values were found at D1 for S1 measuring 5.1 and 5.6 kg ha⁻¹ mm⁻¹ in two years. The yield response factor (Ky) for sesame plants was determined to be 1.27 in the first year and 1.21 in the second year. In conclusion, the findings of this study highlight the significant impact of lateral depth in subsurface drip irrigation on evapotranspiration and water use productivity in Muganlı-57 sesame cultivation. The results indicate that optimizing lateral depth, particularly at 40 cm with mild water stress conditions, can enhance water productivity and overall crop performance under Mediterranean climate conditions.