Growth and Physiological Responses of Pepper in Different Soil Water Regimes and Nitrogen Applications in a Semiarid Agricultural Ecosystem Using Surface and Sub-surface Drip Irrigation and Its Economic Returns

The objectives of this study were to determine the effects of different soil water regimes and nitrogen applications on the yield, leaf water potential (LWP), leaf area index (LAI), stomatal conductance (gs), and chlorophyll content of pepper by applying surface drip (DI) and sub-surface (SDI) drip irrigation during 2015 and 2016 in the Continental region of Turkey. Treatments included three different soil water regimes (full irrigation, FI; deficit irrigations, I₇₅ and I₅₀, receiving 75% and 50% of FI, respectively) and four different nitrogen (N) fertilizer doses (N₀: unfertilized, N₇₀: 70 kg N ha⁻¹, N₁₄₀: 140 kg N ha⁻¹, and N₂₁₀: 210 kg N ha⁻¹). SDI had significantly higher yields in comparison to those obtained by the DI. Yields varied between 21.3 t ha⁻¹ in DI‑I₅₀ and 50.1 t ha⁻¹ in SDI-FI. The highest (4.59 m² m⁻²) and least (1.26 m² m⁻²) LAI were observed in SDI‑I₇₅ N₂₁₀ and DI‑I₅₀ N₀, respectively. FI N₂₁₀ had higher gs in SDI (354.4 mmol H₂O m⁻² s⁻¹) and DI (312.5 mmol H₂O m⁻² s⁻¹), as compared to deficit irrigation treatments. The high yields could be obtained by irrigation using the DI (−1.45 to −1.86 MPa LWP), and the SDI (−1.14 to −1.47 MPa LWP), respectively. The pepper irrigation could be managed by the SDI‑I₇₅ N₁₄₀, leading to the maximum net income. Therefore, pepper irrigation in semiarid regions could be managed by applying the SDI‑I₇₅ N₁₄₀ without negative impacts on the physiological and yield parameters.