Fig. 6. Total water measured in the soil for the top 10 m using one layer (triangle), two-layer (cross), three-layer (square), and three-layer plus interface (circle) calibrations vs. the cumulative applied water (bold line) at all nine monitoring locations during Exp. 2. Between Days 6 and 20, mean RMSE values for the soil measured, using one-layer, two-layer, three-layer, and three-layer plus interface calibration equations, vs. surface applied water are 0.095, 0.067, 0.071, and 0.039 m water, respectively.