Controlled drainage in the Nile delta of Egypt: A promising approach for decreasing drainage off-site effects and enhancing yield and water use efficiency of wheat

Authors: EL-GHANNAM, MOHAMED - Soil, Water And Environment Research Institute (SWERI); WASSAR, FATMA - University Of Gabes; MORSY, SABAH - Damanhour University; HAFEZ, MOHAMED - Icar-Indian Institute Of Maize Research; PARIHAR, CHITTAR - Icar-Indian Institute Of Maize Research; Burkey, Kent; ABDALLAH, AHMED - Damanhour University

Submitted to: Journal of Arid Land
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2022
Publication Date: 3/10/2023
Citation: El-Ghannam, M.K., Wassar, F., Morsy, S., Hafez, M., Parihar, C.M., Burkey, K.O., Abdallah, A.M. 2023. Controlled drainage in the Nile delta of Egypt: A promising approach for decreasing drainage off-site effects and enhancing yield and water use efficiency of wheat. Journal of Arid Land. 15:460-476. https://doi.org/10.1007/s40333-023-0095-3.
DOI: https://doi.org/10.1007/s40333-023-0095-3

Interpretive Summary: Conservation of water resources and efficient use of fertilizers are both critical issues for agriculture in the coming decades. In this study, a USDA-ARS scientist at Raleigh, North Carolina collaborated with colleagues from Egypt, Tunisia, and India to test the effectiveness of a controlled drainage irrigation system in limiting water input into an irrigated wheat crop. The experimental site was a series of agricultural fields with tiled drainage in the Nile Delta of Egypt where the ground water level was at a soil depth of 1.2 meters. When dams were placed in the drain tiles to raise the ground water in test plots to 0.4 meters, irrigation water use was reduced by 40% without affecting wheat yields while retaining a greater proportion of nitrogen fertilizer to support plant growth. The results suggest that, where applicable, controlled drainage is an effective tool to reduce irrigation water inputs and reduce off-site fertilizer contamination.

Technical Abstract: North Africa is one of the most regions impacted by water shortage. The implementation of controlled drainage (CD) in the northern Nile River delta of Egypt is one strategy to decrease irrigation, thus alleviating the negative impact of water shortage. This study investigated the impacts of CD at different levels on drainage outflow, water table level, nitrate loss, grain yield, and water use efficiency (WUE) of various wheat cultivars. Two levels of CD, i.e., 0.4 m below the soil surface (CD-0.4) and 0.8 m below the soil surface (CD-0.8), were compared with subsurface free drainage (SFD) at 1.2 m below the soil surface (SFD-1.2). Under each drainage treatment, four wheat cultivars were grown for two growing seasons (November 2018–April 2019 and November 2019–April 2020). Compared with SFD-1.2, CD-0.4 and CD-0.8 decreased irrigation water by 42.0% and 19.9%, drainage outflow by 40.3% and 27.3%, and nitrate loss by 35.3% and 20.8%, respectively. Under CD treatments, plants absorbed a significant portion of their evapotranspiration from shallow groundwater (22.0% and 8.0% for CD-0.4 and CD-0.8, respectively). All wheat cultivars positively responded to CD treatments, and the highest grain yield and straw yield were obtained under CD-0.4 treatment. Using the initial soil salinity as a reference, the soil salinity under CD-0.4 treatment increased two-fold by the end of the second growing season without negative impacts on wheat yield. Modifying the drainage system by raising the outlet elevation and considering shallow groundwater contribution to crop evapotranspiration promoted water-saving and WUE. Different responses could be obtained based on the different plant tolerance to salinity and water stress, crop characteristics, and growth stage. Site-specific soil salinity management practices will be required to avoid soil salinization due to the adoption of long-term shallow groundwater in Egypt and other similar agroecosystems.