Visualization of the three-dimensional water-flow paths in calcareous soil using iodide water tracer

► We modified a spray method to visualize iodide water tracer in high pH soil. ► The method identified 3-D water-flow paths in calcareous soil after pH adjustment. ► We combine multiple sections to establish 3-D visualization modeling. ► The method is simple, time-saving, low-cost, and widely applicable.