INNOVATIVE SUBSURFACE DRIP IRRIGATION CONFIGURATIONS ENHANCE WATER USE EFFICIENCY AND OLIVE PRODUCTIVITY IN SANDY SOILS

Efficient irrigation management is essential for sustainable olive production in semi-arid regions with sandy soils. This study evaluated three irrigation configurations—conventional surface drip, vertical subsurface drip, and inclined subsurface drip in terms of soil water distribution, crop yield, water productivity (WP), and fruit quality during the 2022–2023 seasons in Egypt. Soil moisture monitoring revealed that the inclined subsurface system provided the most favorable distribution, achieving deeper infiltration (up to 120 cm) and broader lateral spread compared to the vertical and surface systems. Crop yield analysis showed significant improvements under subsurface methods, with the inclined system producing the highest yields (17.9 and 21.9 ton/ha in 2022 and 2023, respectively), significantly outperforming the surface and vertical treatments. Water productivity followed a similar trend, increasing from 2.0 to 2.8 kg/m³ under the inclined configuration, compared to 1.1–1.6 kg/m³ for surface drip. Fruit quality attributes, including fruit, pulp, and seed weights, were also significantly enhanced under subsurface irrigation, with the inclined system consistently producing the largest fruits and heaviest pulp. These findings highlight the superiority of inclined subsurface drip irrigation in optimizing soil moisture dynamics, improving water use efficiency, and enhancing yield and fruit quality, thereby offering a promising strategy for sustainable olive production in arid and semi-arid environments.