T. J. Kelleners

Drastic Disturbance of Salt-Affected Soils in a Semi-Arid Cool Desert Shrubland

Disturbing soils in arid regions can mix subsurface materials with surface soils salvaged for reclamation. Pre-disturbance assessment of soils can minimize impacts of disturbance, and better understanding of drastic disturbance in arid soils will improve reclamation success. Reclaimed well pads have undergone stockpiled soil respreading, tillage, and seeding after drilling is complete. Soil texture and chemical properties were analyzed at 0–15 cm depth in saline and sodic soils from eight paired undisturbed and recently reclaimed sites in the Great Divide Basin of Wyoming. Soil organic matter and structural properties were analyzed in additional samples from two of the paired sites (one sodic, one saline-sodic). Paired difference analysis across the eight well pads indicated that disturbed/reclaimed soils had higher electrical conductivity (EC) than undisturbed soils (12.2 and 3.0 dS m−1, respectively) and higher sodium adsorption ratios (SAR) (26.1 and 1.3, respectively). Analysis of variance of soil organic C (SOC), total N, and soil structural properties indicate that disturbed soils had nearly one-third less total N and two-thirds less SOC than undisturbed soils, and over 65 times more >9.5 mm dry aggregates by weight, representing predominance of large clods in disturbed soils on both sites. Disturbed soils contained significantly smaller proportions of smaller dry aggregate fractions (<53 µm, 53–250 µm, and 250 µm–1 mm) than undisturbed soils, and saturated hydraulic conductivity (Ksat) was about 25% of that in undisturbed soils. Disturbed soils exhibited lower organic materials, higher salt contents, altered soil structure, and low potential for eventually supporting successful native plant communities.

Effects of Cropping Practices on Water-Use and Water Productivity of Dryland Winter Wheat in the High Plains Ecoregion of Wyoming

The conventionally tilled winter wheat (Triticum aestivum L.)-fallow system is often water-use inefficient as its fallow phase has frequently less storage efficiency than no-till and organic production practices. While such alternatives may increase yield while enhancing the health and the water holding capacity of soils, the major limiting factor for dryland production in the semi-arid regions is water. The objectives of this study were to a) determine the water-use and water productivity of dryland winter wheat under conventional, no-till, and organic production practices, and b) study the impact of improved soil-water storage on no-till winter wheat yield. A field experiment consisting of three tillage practices with three replicates was conducted at the University of Wyoming Sustainable Agricultural Research and Extension Center, near Lingle, Wyoming, USA. The wheat yield was higher in the conventional practice than in the other two production practices, and water-use in the former system was higher than the no-till. Water productivity of dryland winter wheat was not affected by the cropping practices. The CERES-Wheat model in the Decision Support System for Agrotechnology Transfer (DSSAT) was used to simulate long-term effects of no-till and conventional-till cropping practices for yield, water conservation, and water productivity. The simulations showed a good agreement between the observed and simulated crop yield and more efficient water conservation and yield production in the no-till than in the conventional practice.

Rainfall, evapotranspiration, and soil moisture as herbage production predictors for Wyoming rangelands

ABSTRACT Rangelands are an important ecosystem in the western US, and herbage and livestock production are important issues throughout the western states. Making stocking rate decisions early in the growing season is difficult because of high variation in annual herbage production. In this study, regression analysis was used to relate herbage biomass to monthly and growing season predicator variables (rainfall, actual evapotranspiration, and soil moisture) using data collected from fifteen Wyoming rangeland sites. Both predictor and response variables were scaled before regression to correct for different physical and environmental conditions between sites. Growing season precipitation was the strongest predictor of herbage biomass production (r2 = 0.79), followed by growing season actual evapotranspiration (r2 = 0.69), and growing season profile-average soil water content (r2 = 0.59). April profile-average (0–90 cm) and April surface (0–30 cm) soil moisture also predicted herbage biomass (r2 = 0.53–0.54), indicating that early growing season soil moisture can be used to inform stocking rate and grazing management decisions as it provides information at the onset of the growing season.

Capillary barriers improve reclamation in drastically disturbed semiarid shrubland

ABSTRACT Soils in arid climates affected by drastic disturbance do not recover without reclamation efforts, and saline-sodic conditions caused by development activities are especially problematic. To improve reclamation success, we created seeded depressions that held three types of sand capillary barriers in October 2013. Sand was placed above (mulch), below (capillary barrier), and encompassing (dual barrier) seeded native soil at ridge and depression sites near Wamsutter, WY, representative of natural gas extraction areas. We compared grass growth, salinity, and moisture among the treatments and under depressions without sand amendments (pit) and plots seeded by standard procedures (control). At the ridge site, the mulch treatment supported 249 stems m−2 in the seeded patches surviving to August 2014, compared with 110 and 89 stems m−2 in the pit and lower barrier treatments, respectively, less than 50 stems m−2 in the dual barrier treatments, and none in the control. The dual barrier and mulch treatments performed best at the depression site, with 40–50 stems m−2 in August compared with none in the other three treatments. Changes in soil moisture and salinity were variable, but indicate positive effects of capillary barriers. Capillary barriers led to reductions or smaller increases in salinity than in treatments without a capillary barrier. While mulch treatments effectively increased grass growth at both sites, the dual barriers only showed positive impact at the depression site, possibly due to adequate moisture. Sand is readily available in many regions, and scaling up from test plots may be achieved with existing equipment.

Analysis of snowpack dynamics during the spring melt season for a sub-alpine site using point measurements and numerical modeling

Snowpack dynamics through October 2014 – June 2017 were described for a forested, sub-alpine field site in southeastern Wyoming. Point measurements of wetness and density were combined with numerical modeling and continuous timeseries of snow depth, snow temperature, and snowpack outflow to identify five major classes of distinct snowpack conditions. Class (i) is characterized by no snowpack outflow and variable average snowpack temperature and density. Class (ii) is characterized by short durations of liquid water in the upper snowpack, snowpack outflow values of 0.0008-0.005 cm hr-1, an increase in snowpack temperature, and average snow density between 0.25-0.35 g cm-3. Class (iii) is characterized by a partially saturated wetness profile, snowpack outflow values of 0.005-0.25 cm hr-1, snowpack temperature near 0°C, and average snow density between 0.25-0.40 g cm-3. Class (iv) is characterized by strong diurnal snowpack outflow pattern with values as high as 0.75 cm hr-1, stable snowpack temperature near 0°C, and stable average snow density between 0.35-0.45 g cm-3. Class (v) occurs intermittently between classes (ii)-(iv) and displays low snowpack outflow values between 0.0008-0.04 cm hr-1, a slight decrease in temperature relative to the preceding class, and similar densities to the preceding class. Numerical modeling of snowpack properties with SNOWPACK using both the Storage Threshold scheme and Richards’ equation was used to quantify the effect of snowpack capillarity on predictions of snowpack outflow and other snowpack properties. Results indicate that both simulations are able to predict snow depth, snow temperature, and snow density reasonably well with little difference between the two water transport schemes. Richards’ equation more accurately simulates the timing of snowpack outflow over the Storage Threshold scheme, especially early in the melt season and at diurnal time scales.