Assessment of current and future (under climate change) crop water requirement and irrigation strategies under bubbler irrigation system for date palm in Jemna oasis, Southern Tunisia

Oases of southern Tunisia are located in a hostile arid environment. Despite the environmental situation, oases are the place of specific knowledge developed by indigenous populations. Theses agroecosystems, where date palm tree is the dominant crop, are a characteristic example of Saharan arid climate region. Nowadays, oasis land is threatened by soil and water degradation under salinity risk as well as water scarcity, identified as the most important problem for regional and national socio-economic security. The advancement of technologies that ensure efficient use of irrigation water may be needed. This work is evaluating the bubbler irrigation system in Jemna Oasis (southern Tunisia) for date palm for current and future climate. The objective was to quantify root water uptake, yield production and root zone salinity under current and future climate change. Mid and long term precipitations, temperature and date palm water needs were determined from 2 regional climate models forced by general circulation model (GCM-RCMs) issued from EURO-CORDEX project. Field experiments and modelling approach were developed within this work. Different scenarios regarding irrigation frequencies and quantities were tested using Hydrus-1D model. In context of water scarcity, implementing an irrigation schedule in which crop growth stages and soil salinity are considered is strongly recommended for date palm tree. The bubbler irrigation system using 100 % ETc and T₃ as irrigation schedule could be considered as a save irrigation method under current and future climate change, if water allocated for irrigation do not exceed 3.2 dSm^-1 with crop yield reaching equal to 80% as a mean value and soil salinity about 12dSm^-1. Results indicated that  climate change from 2020 to 2090 would increase temperatures and decrease annual rainfall. An increase in events with rainfall amounts exceeding 100 mm/day is noted. During this future period, using both saline irrigation water (5 and 5.5 dSm^-1) and irrigation lower than 100% ETc, the date palm crop yield is expected to vary from an average value of 81% in 2020 to about 70 % in 2050 and 55% in 2090 and an increase of soil salinity to 20 dSm^-1 will occur.