A simple Capillary Device for Real-time Monitoring of barley water requirements under arid environment

Abstract In Algeria, as in many other developing countries, irrigation faces major challenges, including water wastage, overexploitation of groundwater, and soil salinization—primarily due to inadequate water management practices. Achieving efficient irrigation relies on the precise estimation of crop water requirements. However, this is often lacking, as it depends on accurate assessments of the reference evapotranspiration (ET₀) and the experimental determination of crop-specific coefficients using high resolution lysimeters. This study aims to develop and evaluate a simple, low-tech irrigation scheduling system based on the wick irrigation technique. The proposed system—a Low-Tech Self-Watering Capillary Device (LTSWCD)—enables real-time measurement of the crop evapotranspiration (ETc) of a selected crop (barley) grown in a one-square-meter micro-plot under arid conditions. The amount of water consumed over several days is then directly applied to larger experimental blocks. Daily measurements were compared to the standard barley estimates recommended in the FAO-56 guidelines, and irrigation scheduling was studied under two treatments: 100% (full irrigation) and 130% (over-irrigation) of the water depth recorded by the LTSWCD. The main results reveal that the measured crop evapotranspiration (ETc) captured the same trend as the based FAO56-PM ETc at different time intervals, with a correlation coefficient R = 0.95 at weekly and RMSE = 4 mm week -1 . The seasonal Bareley’s measured ETc was 327 mm, and the obtained Kc shows a good agreement with the standard Kc. Moreover, under two irrigation treatments (100 and 130%), barley’s grain and straw yields show no significant differences at a 0.05 significance level, which demonstrates that increasing irrigation beyond the measured crop water needs does not significantly enhance barley yields under the conditions of this experiment. These results highlight, in the absence of high-resolution lysimetric data, the effectiveness of the LTSWCD as a simple device that farmers could use to directly measure real-time irrigation water requirements under conditions similar to those in the study area.