Yield and quality response of surface and subsurface drip-irrigated eggplant and comparison of net returns

Yield and quality response to various irrigation regimes applied with subsurface and surface drip systems on eggplant and net profit generation in the Mediterranean Region of Turkey was evaluated. Surface drip (DI) and subsurface drip systems (SDI); two irrigation frequencies (IF3: 3-day; IF6: 6-day) and four irrigation regimes (Full irrigation, FI; deficit irrigations, DI50; DI75; and Partial Root-zone Drying PRD50, which received, respectively 50, 75 and 50% of FI) were tested in a split-split plot design. In general, SDI used slightly less water than the surface drip plots due to reduced evaporation losses from the soil surface. Irrigation systems, intervals and regimes resulted in significantly different yields and quality. The results showed that surface drip resulted in higher eggplant yield than SDI by 7.3 and 11% for 3-day and 6-day irrigation frequency in 2013, but the two systems performed similarly in 2014. IF3FI treatments under both drip systems produced significantly greater yields than other irrigation regimes. Water stress reduced eggplant yield significantly and PRD50 treatments resulted in the lowest yields in both growing seasons. Fruit weight, volume and number increased but fruit dry matter, total soluble solids and water productivity decreased with increasing irrigation. The highest water productivity (WP) was found in DI50 under subsurface drip 6-day interval (SDI IF6 DI50) and the lowest in PRD50 under subsurface drip 6-day interval (SDI IF6 PRD50). IF3 FI in the surface drip system generated the highest net income followed by IF3FI in SDI. In case of water scarcity, IF3DI75 is recommended for high yields and higher net income in the Mediterranean region.