Field Measurements and Simulation of Deep Percolation in Two Different Soils.

Deep percolation below the crop root zone is important for groundwater recharge in irrigated lands with shallow aquifers. This study took place at New Mexico State University’s Sustainable Agriculture Science Center in Alcalde, NM.  The objectives of this study were to determine deep percolation below the root zone in two different soils after surface irrigation and to evaluate the performance of HYDRUS-1d in simulating field-measured results. One oat field was established in each of two predominant local soil types that overlie a shallow aquifer. The depth to water table ranged from 2.6 to 4.0 m depending on the proximity to a nearby river. Two 100 m by 100 m fields were instrumented to measure soil water content and shallow groundwater level in a Fruitland sandy loam field and in a Werlog clay loam field. The two fields were flood irrigated with irrigation depths ranging from 4 to 22 cm. Field data were used to calculate velocity of propagation of the wetting front, water fluxes, deep percolation below the root zone, and water level response following irrigation. Water transport was simulated after surface irrigation using HYDRUS-1d. Field-measured results showed relatively higher levels of propagation of the wetting front and water flux in the sandy loam soil when compared to the clay loam soil. Also, deep percolation was higher in the sandy loam than in the Werlog clay loam soil. Minimal shallow ground-water response was only observed towards the end of the irrigation season in the clay loam soil. HYDRUS-1d was able to simulate water transport through the root zone successfully.