Project Number: 3096-13000-009-02-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2018
End Date: Jun 30, 2022
This agreement supports the Ogallala Aquifer Program, an ARS led research program, in cooperation with different scientists at Texas Tech University. The decline of the water table in the Ogallala Aquifer has prompted us to address the following two questions. First, what are the seasonal changes of ground water quality in selected irrigation wells in the Ogallala Aquifer? Second, as this region transitions from deficit irrigation to dryland production how can we make better use of the rainfall? These objectives and resulting research results are in line with the action plan of ARS’ NP-211 Water Availability and Water Management.
This cooperative project, between ARS Lubbock and Texas Tech University, will address research on the two objectives, i.e., continue the sampling of 20 irrigation wells and to process collected soil samples. This information is key to understand how the quality of the water from the Ogallala Aquifer may impact crop production and how to increase the storage of rain in the soil so that it can subsequently be used for crop production. The results from this research are applicable to other regions that are subject to an increasing demand on the water supply. Experimental approaches for each of the two objectives follow. For the first objective, twenty irrigation wells across five counties in the Texas High Plains were sampled on a two-week interval for depth to the water table and water samples were collected from each well and placed in 60 mL vials. The electrical conductivity (EC) of each water sample was measured with a conductivity sensor and the sample was stored for subsequent analysis of salts, i.e., sodium, calcium and magnesium. We plan to continue this sampling protocol to establish a time-series of emerging patterns that develop and provide guidelines of the suitability of the irrigation water for crop production. For the second objective we will process soil samples that were collected in 2017 and 2018. These samples were obtained along two 300-m transects. One transect, was in a North to South direction and the other transect was in an East to West direction. The sampling interval was 10 m, i.e., 30 sampling points per transect for a total of 60. Every 10 m, samples were obtained to a 1.8 m depth. The first 0.15-m depth was sampled every 0.05 m (6 sub-samples), and from 0.3 to 1.8 m depth, every 0.15 m (10 sub-samples). This translates to 16 sets per 10 m, or 480 samples per transect for a total of 960 samples. These transects were obtained near Littlefield, TX on an Olton soil series across a field that was enrolled in the Conservation Reserve Program for more than 20 years and dryland production. For each soil sample we will measure, gravimetric water content, soil texture, pH, EC, total N and C. On selected samples we will measure the saturated hydraulic conductivity and the soil water content release curve. All these measurements will be done using standard and recommended laboratory procedures. In addition, the volumetric soil water content in the 0.05 m surface layer was measured using a dielectric based sensor that allows the calculation of the surface soil density. The surface soil layer at each 10 m will be sampled for soil micro-organisms. Data analysis will be done using spatial statistics, e.g., cross correlation, semi-varianceand, auto regression and standard statistical procedures, all the moments of the mean.