Evaluating Soil Water Redistribution under Mobile Drip Irrigation, Low-Elevation Spray Application, and Low-Energy Precision Application Using HYDRUS

A study to assess soil water redistribution under mobile drip irrigation (MDI), low-energy precision application (LEPA), and low-elevation spray application (LESA) was conducted under a center-pivot irrigation system. Water application devices included MDI (${\mathrm{MDI}}_1$ and ${\mathrm{MDI}}_2$ flow rates of 3.7 and $7.6\mathrm{L}/\mathrm{h}$, respectively), LEPA bubbler, and LESA spray. Measured soil water content was used to calibrate HYDRUS (2D/3D) version 2.05.0270, which was then used to simulate water redistribution within the soil profile after irrigation by MDI, LESA, and LEPA. Results showed that for all the devices, the effect of irrigation was mostly limited to the top 60 cm of the soil profile 72 h after irrigation. MDI driplines and LEPA showed the highest lateral soil water redistribution. The mean soil water contents for ${\mathrm{MDI}}_1$, ${\mathrm{MDI}}_2$, LEPA, and LESA at a depth of 30 cm were 0.31, 0.31, 0.31, and $0.33\mathrm{cm}·{\mathrm{cm}}^{-3}$ respectively; at a depth of 60 cm the corresponding values were 0.28, 0.28, 0.26, and $0.28\mathrm{cm}·{\mathrm{cm}}^{-3}$, respectively. The interquartile range of soil water content at 30 cm for ${\mathrm{MDI}}_1$ and ${\mathrm{MDI}}_2$ was $0.04\mathrm{cm}·{\mathrm{cm}}^{-3}$; the value for LEPA was $0.02\mathrm{cm}·{\mathrm{cm}}^{-3}$. The results indicated greater nonuniformity under MDI than under LESA. The results also showed that the MDI water redistribution pattern was similar to that of LEPA, but horizontal uniformity was less than with LESA. MDI had 48% and 19% less runoff potential compared with LEPA and LESA, respectively. Although soil water redistribution uniformity under MDI was less than under LESA and LEPA, it enabled better infiltration and lessened runoff potential.