Enhancing Water Use Efficiency in Subsurface Drip Irrigated Citrus Trees Using Wrapped Drip Irrigation Lines and Soil Covers

Water scarcity and climate change significantly affect food production in Egypt. To better understand and limit these effects, this study aims to investigate new technology for water saving under climate change conditions. Subsurface drip irrigation integrated with regulated deficit irrigation (RDI) helps reduce crop evapotranspiration (ETc) by 25% compared to full irrigation requirement (FI) in the six soil cover materials studied: sand (C1); clay (C2, control); compost (C3); 50% sand+50% clay (C4); 50% compost +50% clay (C5); and 50% sand+50% compost (C6). Soil cover materials were used to reduce the evaporation from the soil surface under wrapped drip lines and inline drippers (at 2.2 L h−1 at 1 bar). The results revealed that yield as well as water use efficiency (kg m−3) significantly increased (p-value 0.05) under C6 due to improved soil moisture distribution in the root zone. The yield under C6 was 21% and 18% higher than the control for 2021 and 2022, respectively. The soil cover type also significantly affected the amount of seasonal crop water consumption. Significant savings in applied irrigation water by 12.8% and 12.5% were observed under C6 as compared to the control, in the growing seasons 2021 and 2022, respectively. Wrapped drip lines were better than inline drippers for all tested parameters. The RDI has led to a significant (p<0.05) increase in water savings by 14.7% and 13.2% in 2021 and 2022, respectively. The highest soil water content values in soil profile after irrigation event after 2 days were 30.35±0.86 (cm3 cm−3) achieved under C6, while the lowest values were 27.8±0.45 (cm3 cm−3) under C3 and C1.