A Simple Capillary Device for Real-Time Water Requirement Monitoring of Barley under Arid Conditions 

Abstract Irrigation is crucial for crop production, especially in arid and semi-arid regions. Poor irrigation management leads to low water use efficiency, particularly in areas vulnerable to the adverse effects of climate change, where water resources are diminishing. In Algeria, agriculture accounts for 64% of freshwater withdrawals, irrigation faces major challenges such as water wastage, soil salinization, and groundwater overexploitation. Commonly effective irrigation requires indirect estimation of crop water needs, which relies on crop coefficient Kc and reference evapotranspiration ET₀. This study aims to develop and test a simple, low-tech irrigation scheduling system based on wick irrigation technic. The proposed system, a low-tech self-watering capillary device (LTSWCD), enables real-time measurement of crop water needs (ETc) of a selected crop (barley) grown in a one-square-meter micro-plot. Then the amount of water consumed over a few days is directly applied to larger experimental blocks. The daily measurements were evaluated relative to barley’s standard estimates, recommended in FAO56 paper, and irrigation scheduling were studied under two irrigation treatments: 100% (full irrigation) and 130% (over-irrigation) of the water depth recorded by the LTSWCD. The main results indicate that the measured crop evapotranspiration (ETc) follows the same trend as the FAO56-PM-based ETc across different time intervals, with a correlation coefficient (R) of 0.95 at the weekly scale and an RMSE of 4 mm per week. The seasonal measured ETc for barley was 327 mm, and the obtained crop coefficient (Kc) was consistent with the FAO standard values. Moreover, under two irrigation treatments (100% and 130% of crop water requirements), no significant differences (p > 0.05) were observed in barley grain and straw yields. This suggests that increasing irrigation beyond the measured crop water needs does not significantly enhance barley yields under the conditions of this experiment. These findings highlight the effectiveness of the LTSWCD as a simple and reliable tool for accurately measuring real-time irrigation water requirements.