Geophysical Studies of the Characteristics of Fluvial and Desert Soils in Rio Grande Valley of West Texas and Southern New Mexico

Agriculture in arid lands, such as in the Rio Grande Valley in west Texas, relies on flood irrigation. However, flood irrigation can cause salt buildup and greenhouse gas emissions associated with pedogenic carbonate precipitation. The ability of irrigation to promote crop growth is influenced by geochemical and hydrological processes controlled, in part, by soil grain size, larger-scale soil structure, and mineralogy. This study investigated soils from 3 regions 1) A pecan orchard in the river valley of Tornillo, TX, with soil derived from fluvial deposits, undergoing flood irrigation every 2 to 3 weeks in spring through fall, 2) The El Paso Water Utilities Well-field in Canutillo, TX, also in the river valley but not farmed in over 70 years and 3) A piedmont – slope site at the Jornada Experimental Range northeast of Las Cruces, NM with upland soil that has been grazed but never farmed. This study utilized shallow geophysical methods (e.g., ground conductivity, magnetics, and resistivity) for 1) measuring various soil properties (soil texture, salt buildup, water table depth, and water flow patterns), 2) determining how texture and structure influence soil changes (e.g., salt buildup, pedogenic carbonate buildup, moisture retention) during irrigation cycles at the pecan grove, and 3) comparing the variability of these properties to understand the impact of agricultural practices on soils and crop growth. Soil texture firmly controls the physical, hydrological, and chemical properties of soils. At the pecan orchard, previous geological, geochemical, and geophysical data indicated finer soils and salt buildup contribute to the pecan trees\u27 unequal growth. However, we note a “Goldilocks effect” because, at the well-field, the fine soil holds the water necessary to support the vegetation at the site that is not already undergoing irrigation or agricultural practices. Finally, at the Jornada experimental range, specifically the Piedmont site, a relationship between the topography, depth to caliche, and vegetation is influenced by hydrological processes where caliche acts as a barrier to water movement