Effects of root watering system on yield, water use efficiency and fruit quality of date palm (c.v. Siwi): a case study in the arid climate, Egypt

The objective of the study is to determine the effects of root watering systems (RWS) with drip irrigation systems (DIS) and bubbler irrigation systems (BIS) on yield, water use efficiency (WUE) and fruit date palm (Phoenix dactylifera L.) quality under the different water regimes of 60, 80 and 100% of total water requirements (TWR). The experimental fieldwork was conducted during two successive seasons (2019/2020–2020/2021) in a farm at El-kharga Oasis, New Valley Governorate, Egypt. The evapotranspiration (ETo) was calculated based on the Penman–Monteith (P–M) equation from which the climatic data was retrieved from the El-kharga climatic station. The results showed that, the maximum productivity was 103 kg/tree in the second season under RWS at 100% of TWR, while, the minimum productivity was 62 kg/tree in the first season under BIS at 60% of TWR. Furthermore, the maximum WUE was 1.61 kg/m3 under RWS for 60%. The minimum WUE was 0.94 kg/m3 under BIS for 100%. The percentage of increase in WUE between the maximum and minimum values under three systems was 41.6%. The results indicated that the amounts of applied water markedly decreased in the order of RWS < DIS < BIS and increased productivity and WUE in the order of RWS > DIS > BIS. Fruit quality was significantly affected by the type of irrigation system, with the best quality obtained with the RWS followed by the DIS and then by the BIS. The RWS system, through its positive impact on water use efficiency and enhancement on fruit yield and fruit quality of date palm, seems quite suitable for the irrigation of palm trees in arid and semi-arid regions.