Southern High Plains Research Articles

The dual role of low-carbon ammonia in climate-smart farming and energy transition

The changing climate poses unprecedented risks and challenges to agricultural production and energy systems worldwide, necessitating innovative technology and policy solutions that transcend traditional boundaries. This paper highlights the critical intersection of energy and agricultural systems and identifies low-carbon intensity ammonia (LCIA) as a pivotal element in reducing the carbon footprint of US agricultural production, particularly in fertilizer use. It presents a comprehensive analysis of the ammonia market and value chain, emphasizing its potential to decarbonize agricultural fertilizers and serve as an alternative clean energy source. The technical review covers various ammonia production methods, from natural gas-based processes with carbon capture and storage to electrolysis using renewable energy. These methods’ economic and environmental implications are examined to provide insights into the levelized costs and emissions of LCIA applications across various scenarios. A case study focusing on the Permian Basin and Southern High Plains regions is conducted to illustrate the regional synergy between the agriculture and energy sectors, proposing a framework for integrating LCIA into the US agricultural sector. The proposed framework, Sustainable Ammonia for Resilient Agriculture, outlines policy recommendations and strategic investments to overcome market and infrastructure barriers, aiming to develop a resillient and sustainable LCIA value chain. Future research direction should emphasize the need for local value chain development plans encompassing agriculture, energy, infrastructure, and workforce development under a unified policy framework.

Influence of Grazing on Canola Grain, Canola Forage Yield, and Beef Cattle Performance

Interest is increasing in grazing winter canola (Brassica napus) as an alternative crop in winter wheat (Triticum aestivum) rotations in the Southern High Plains (SHP) of the USA and similar environments. In this stidy, winter cereal rye (Secale cereale) and winter canola pastures (forage) were compared for two winter growing seasons at New Mexico State University’s Rex E. Kirksey Agricultural Science Center at Tucumcari, NM, USA, to determine the relative effect of pasture type on late-gestation beef cows and growing yearling cattle, along with the effect of grazing on canola grain production. Canola grain yields were reduced by 25% when canola was grazed until removal approximately one month after grazing was initiated, but before the onset of rapid regrowth after winter (641 vs. 486 kg grain ha−1 for never grazed or grazed canola, respectively, p < 0.0256). No differences existed for forage mass, nutritive value, or animal performance, although forage mineral composition of canola could be a concern. Grazing winter canola as a dual-purpose crop in the SHP and similar environments is feasible when proper grazing management is applied; producers should anticipate a 20–25% reduction in grain yield, but expect animal gains to offset that loss.

Diet specialization mediates drivers of Cucurbita herbivory in a semi-arid agroecosystem

Herbivory is a major fitness pressure for plants and a key driver of crop losses in agroecosystems. Dense monocultures are expected to favor specialist herbivorous insects, particularly those who primarily consume crop species; yet, levels and types of herbivory are not uniform within regional cropping systems. It is essential to determine which local and regional ecological factors drive variation in herbivory in order to support functional agroecosystems that rely less on chemical inputs. Crops in the genus Cucurbita host a suite of both generalist and specialist herbivores that inflict significant damage, yet little is known about the relative contribution of these herbivores to variation in herbivory and how local- and landscape-scale Cucurbita resource concentrations, management practices, and natural enemies mediate this relationship. In this study, we tested whether three foundational ecological hypotheses influenced Cucurbita herbivory across 20 pumpkin fields in the semi-arid Southern High Plains Region of Texas. We used generalized linear mixed models and confirmatory path analysis to assess whether the Density-dependent Herbivory Hypothesis, Resource Concentration Hypothesis, or the Natural Enemies Hypothesis, could explain variation in Cucurbita herbivory and insect dynamics in the context of conventional agronomic practices. We found that herbivory increased over time, indicating that herbivores were causing sustained damage throughout the growing season. We also found that fields with higher local Cucurbita resources had lower herbivory, suggesting a resource dilution effect. Natural enemy communities were more abundant and taxonomically rich in sites with greater generalist herbivore abundance, though predator abundance declined over time, indicating that late-season crop fields are most at risk given high herbivory and low natural enemy-based control. Our findings also suggest that while local resource availability may drive the abundance and richness of arthropod communities, additional agronomic and phenological information is needed to anticipate herbivory risk in an agriculturally dominated landscape.

USEPA CALPUFF validation and dispersion modeling of beef cattle feedlot PM10 and PM2.5 emissions factors

Beef cattle feedlots are major sources of criteria air pollutants in the United States. To aid stakeholders in air quality modeling, emissions factors for animal waste-producing facilities are under development by the U.S. Environmental Protection Agency (USEPA). However, beef cattle feeding operations (feedlots) are not among facilities surveyed under the associated USEPA National Air Emissions Monitoring Study (NAEMS). Authors aim to supplement NAEMS through development and validation of particulate matter (PM10 and PM2.5) emission factors from a previous sampling campaign of five large feedlots in the Southern High Plains of North America via USEPA's CALPUFF dispersion model. PM concentrations were higher overall during the warm season (March–August; PM10 = 692 ± 507, PM2.5 = 114 ± 110 μg/m3) relative to cool season (November–January; PM10 = 102 ± 105, PM2.5 = 12.2 ± 8.6 μg/m3), and overall median PM10 and PM2.5 emission factors were 48.2 (day = 33.8, night = 72.4) and 5.22 (day = 8.4, night = 3.1) mg/m2/hr, respectively. Validated emissions factors were then used to model diurnal peaks and long-range transport (100 km maximum extent). Peak concentrations were most frequently observed between 2000 and 0600 h (93.9%; mean 1-hr peak ± SD = 1119 ± 1240 μg/m3) for PM10 and 1600-0600 h (80.0%; mean 1-hr peak ± SD; 178 ± 174 μg/m3) for PM2.5. Four of five feedlots exceeded ≥1 primary PM National Ambient Air Quality Standard (NAAQS) at receptors (2-m height) over a 5-km spatial extent during the modeling period (November 2010–August 2011). Moreover, present estimates of feedlot-derived inhalable PM represent human and environmental exposure pathways currently exempt from Clean Air Act monitoring and reporting standards, and spatial interpolation of federal air quality monitors cannot adequately characterize inhalable PM concentrations in non-metropolitan municipalities and unincorporated rural communities.

Semi-arid soil bacterial communities are refined by altered plant selection pressure under conservation management practices

Plants' ability to select for, and refine, their microbiome over time is well known. In soil, the strength of plant selection pressure on microbial composition can result in distinct rhizosphere, and root-zone communities, but may be masked in soils with lower native diversity such as semi-arid soils. Semi-arid soils are also known for their high potential for wind erosion, which may be mitigated by the implementation of cover crops. These cover crops may also alter the microbial composition of the semi-arid soils, but the strength of this effect, and the resulting changes in the composition of the microbiome, are less well known. This study aimed to address whether the implementation of a single-species wheat cover crop in semi-arid agricultural soils would impact the bacterial composition of the cash crop. We investigated three tillage regimes—no-tillage with a winter wheat cover crop, no-tillage winter fallow, and conventional tillage winter fallow—to determine the effects of tillage removal, and cover crop implementation on the soil bacterial community present in the root zone of the cash crop. It was determined that the composition of the bacterial microbiome was similar between cover cropped and non-cover cropped treatments. The similarity of bacterial composition was likely due to the strong effect of environmental selection reducing overall biodiversity in these soils. However, the variability of bacterial community composition was strongly reduced for the cover cropped treatment compared to the two non-cover cropped treatments. The similarity of bacterial communities with cover cropping, without significant soil physicochemical changes, suggests that plant-selection pressure, rather than management-induced changes in soil physicochemical properties, drove the refinement (decreased dissimilarity compared to non-cover cropped treatments) of the bacterial community. The composition of this refined community under cover cropping was determined to contain an enrichment of several genera of interest including N cycling and potential plant-growth promoting bacteria. In summary, the introduction of cover cropping in the nutrient and microbial-poor soil of the semi-arid Southern High Plains strongly refined the bacterial community and selected for organisms with the potential to improve soil functions associated with greater agronomic sustainability.

Soil Health Assessment to Evaluate Conservation Practices in SemiArid Cotton Systems at Producer Site Scale

Maintaining soil health and sustainable crop production has been challenged by climate variability and wind erosion in semi-arid regions. To understand the initial effects of the transition of tilled cotton systems to no-tillage with winter wheat as a cover crop, we sampled 18 commercial grower sites from 2019 to 2022 in the Southern High Plains (SHP). We evaluated the soil biological component, which often responds rapidly to changes in residue additions or minimized soil disturbance providing an early indication of changes in soil health, especially in the low organic matter soils in this region. After two years, compared to tilled systems, no-till systems had significant increases in ester-linked fatty acid methyl ester (EL-FAME) bacterial and saprophytic and AMF fungal markers, enzyme activities of nutrient cycling, and various SOM pools, under both center-pivot irrigation and dryland. Similar increases were also observed in two dryland sites sampled before and up to two years after transition to no-till. Our study demonstrates the potential of no-tillage and cover crops to improve soil health in cotton production in semiarid regions, and a framework for a soil health assessment that links different soil health indicators with functions related to soil organic matter, soil water, and biogeochemical cycling.

Seasonal Abundance and Habitat Associations of American Kestrels on the Southern High Plains of Texas

ABSTRACT American Kestrel (Falco sparverius) populations are generally declining across the species' North American distribution but the population in the Southern High Plains region currently appears to be stable. Historical evidence suggests the region formerly had a low abundance of kestrels, and that their current numbers are due to landscape changes associated with European settlement. We conducted monthly surveys for American Kestrels across 2 yr to estimate seasonal densities and identify land cover associations in the Southern High Plains of Texas. We found an overall estimated density of 0.99 birds/km2 (95% CI = 0.406, 1.582) across the 2-yr period, with seasonal estimated densities highest in autumn and winter (0.92–2.53/km2), and lowest in spring (0.49–0.67/km2). Whereas other studies have found that temperature influenced detection of wintering kestrels, we found an interaction of drought conditions and snow most strongly influenced the number of kestrels in our study area. Kestrels largely used land cover types in proportion to availability but there was some evidence of seasonal shifts. Generally, they tended to avoid cotton fields and sometimes selected for areas with woodlots, abandoned or occupied houses, and barns, all of which likely provided nesting and roosting opportunities. Our study provides the first contemporary assessment of seasonal abundance and habitat associations of American Kestrels in the Southern High Plains, where their presence and abundance has been unintentionally facilitated by landscape changes following settlement. We provide a baseline for population monitoring and studies assessing response to additional landscape changes (e.g., development of wind energy facilities) and a changing climate.

Small rails from the late Quaternary of the Southern High Plains and their palaeoenvironmental context

The fossil record of birds from the Quaternary Period (2.58 mya to present) of North America sheds light on modern patterns of diversity and geographical distribution. Fossils from the late Pleistocene and early Holocene document the presence of multiple species of small rails on the Southern High Plains. Black Rails, Virginia Rails and Soras occurred throughout regional drainages from ~ 11 000 to 8500 years ago. Age and palaeoenvironmental data associated with the rail remains provide temporal and ecological context. Those data link the past populations to extant populations occurring as migrants to the region today. The total record reveals that Black Rails, Virginia Rails and Soras occur on the Southern High Plains today despite major changes in climate, environments, biota and habitats since the late Pleistocene–early Holocene. Anthropogenic changes to regional wetlands in the present day threaten the occurrence of small rails across the Southern High Plains.

Collecting Rocks on the Frontier: Investigating the Geodiversity Significance of Historical Building Stones and Rock Collecting at the Maxey Homestead, Northwest Texas, USA

The geoheritage importance of the stones used in the construction of buildings in urban landscapes has been documented by several scholars around the world. Building stones can provide an ex situ cross-section of a region’s geodiversity and illuminate its cultural significance. Research at the historic Maxey Homestead (1902–1907), located along the eastern escarpment of the Southern High Plains near Post, Texas, has uncovered a rock collection gathered from local sources. In addition, rocks from the eastern escarpment were used to construct and decorate a house in 1938 (~9 km to the north) after the Maxeys moved from their original homestead. A combination of GIS and 3D mapping using an unmanned aerial vehicle were used to assess and analyze the geodiversity significance of the rock collection and rock-decorated house. Rock collecting and the use of local stones in building construction provide insights into the geodiversity of the Southern High Plains’ eastern escarpment and the historical geoheritage of northwest Texas in the early 20th century. The results of this study also demonstrate the importance of examining non-urban and historical landscapes for elucidating the significance of geodiversity to past peoples.

Nitrogen fertilizer driven nitrous and nitric oxide production is decoupled from microbial genetic potential in low carbon, semi-arid soil

IntroductionNitrous oxide (N2O) emission from soil is a major concern due to its contribution to global climate change and its function as a loss mechanism of plant-available nitrogen (N) from the soil. This is especially true in intensive agricultural soils with high rates of N fertilizer application such as those on the semi-arid Southern High Plains, USA.MethodsThis study examined emissions of N2O, pore-space concentrations of N2O and nitric oxide (NO), soil chemical properties, water content, and the genetic potential for N cycling five years after conservation system and N management implementation.ResultsFor these semi-arid soils with low N, carbon, and water contents, large soil N2O emissions (up to 8 mL N2O-N m-2 day-1) are directly related to the application of N fertilizer which overwhelms the N2O reducing capacity of the soil. When this fertilizer N is depleted, N2O flux is either low, non-existent, or net-negative and has been observed as early as mid-season for preplant applied N fertilizer (-0.1 mL N2O-N m-2 day-1). Soil pore-space gas concentrations (N2O and NO) remained relatively constant across the growing season (average N2O: 0.78 µL N2O L-1 soil air; NO: 3.3 µL NO L-1 soil air, indicating a base-level of N-cycle activity, but was not directly related to surface emissions of N2O which decreased across the growing season. In addition, genetic potential for N cycle activities increased across the growing season simultaneously with stagnant/reduced N cycle activity. This reflects the difficulty in relating genetic potential to in-situ activity in field research.ConclusionIt is likely that in a nutrient and carbon-poor soil, such as the semi-arid agricultural soil in this study, the microbial processes associated with N cycling are mostly limited by inorganic-N and less directly related to genetic potential at the time of sampling.

Characterizing Evaporative Losses From Sprinkler Irrigation Using Large Weighing Lysimeters

Highlights Losses for MESA and LESA were comparable on the day of irrigation and oftentimes greater for the subsequent day. Losses were greater due to incomplete canopy conditions for both MESA and LESA on both days. Evaporative losses from irrigation extended to at least the subsequent day following irrigation in most cases. Losses over two days accounted for as much as 39.5% and 28.0% of irrigation depth for MESA and LESA, respectively. Abstract. Effective irrigation systems that increase crop water productivity by minimizing evaporative losses are paramount for extending the longevity of finite groundwater resources in the semi-arid U.S. Southern High Plains (SHP). Although subsurface drip irrigation (SDI) acreage has increased in recent years, center-pivot sprinkler systems still account for greater than 85% of the irrigated area in the SHP. Modern sprinkler configurations are typically classified according to application height as either mid-elevation spray application (MESA) or low-elevation spray application (LESA). While application drift and evaporative losses are easily measured under fallow conditions, quantifying evaporative losses under cropped conditions is difficult. Lysimeter-derived daily evapotranspiration (ET) values for SDI-irrigated and sprinkler-irrigated fields planted to corn in 2016 (MESA) and 2018 (LESA) near Bushland, TX, were compared for days when sprinkler irrigation events occurred and for subsequent days, when possible. Differences (extra ET) were attributed to evaporative losses associated with MESA and LESA irrigation. Average daily extra ET values for both sprinkler irrigation methods were similar on the day of irrigation, although MESA was slightly larger than LESA at 1.4 and 1.2 mm, respectively. The average daily extra ET values for incomplete canopy conditions were 2.2 mm for MESA and 1.9 mm for LESA, while values were identical for both methods at 0.6 mm for full canopy conditions. Average daily extra ET values were also expressed as a percentage of daily standardized grass reference ET (ETos) values. Average values for MESA and LESA were 20.1% and 13.5%, respectively, for the season, with similar findings of 29.3% and 19.4% for incomplete canopy conditions. Average extra ET/ETos values for incomplete canopy conditions were similar at 7.5% and 7.7% for MESA and LESA, respectively. Evaporative irrigation losses, calculated as the percentage of extra ET to irrigation depth, were slightly larger overall for the day of irrigation for MESA (5.4%) than LESA (5.2%). Losses of 7.9% and 7.0% were observed for incomplete canopy conditions for MESA and LESA, respectively. Average losses for LESA (3.5%) under full canopy conditions were greater than those for MESA (1.9%). A comparison of extra ET values for days following irrigation revealed that evaporative losses from irrigation events extended beyond the day of irrigation. MESA extra ET values for the day following irrigations increased by 57.1% (2.2 mm) overall, 13.6% (2.5 mm) for incomplete canopy conditions, and 150.0% (1.5 mm) for full canopy conditions. The same was true for LESA, with increases of 125.0% (2.7 mm) overall, 78.9% (3.4 mm) for incomplete, and 216.7% (1.9 mm) for full canopy conditions. Summing of extra ET values for the day of irrigation and the subsequent day yielded average values more than double those for the day of irrigation only, at 3.9 and 4.3 mm for MESA and LESA, respectively. Similarly, values for extra ET as a percentage of irrigation depth were also more than double those for the day of irrigation only, with the greatest loss values of 39.5% for MESA and 28.0% for LESA. These findings suggest that although LESA appears to mitigate evaporative losses marginally more in corn than MESA on the day of irrigation, considerably more evaporative losses occurred for both methods during the subsequent day, with slightly increased losses for LESA, resulting in little difference between overall losses over the two days. This may in part be explained by the temporary cooling effect of the irrigation inside the canopy on the day of irrigation, which is diminished by the second day. A greater discrepancy between evaporative losses for MESA and LESA is likely to be observed for crops having shorter stature or lower leaf density, such as cotton, although more study is needed to corroborate this claim. Knowledge of these findings provides useful information for both producers and water managers when considering irrigation management and water planning strategies. Keywords: Evaporation, Evapotranspiration, LESA, MESA, Semi-arid, Sprinkler Irrigation, Subsurface Drip Irrigation, Transpiration, Weighing Lysimeters.

Modeling management of continuous dryland cotton with an intervening winter wheat cover crop in a semiarid climate

Although winter cover crop residue can mitigate the stresses of dryland production in semi-arid regions, cover crops can also reduce soil moisture and cash crop yields. In some field studies of dryland cotton grown after terminated winter wheat in the U.S. Southern High Plains (SHP) and Texas Rolling Plains cotton yields were increased relative to continuous cotton, while others had no significant yield or soil water effect. These uncertain outcomes may be due to the trial's limited sampling of seasonal rainfall conditions. To estimate the probabilities of cover crop effects under more representative SHP climate conditions, 294 station-years of crop model simulations of terminated winter wheat followed by dryland cotton were conducted. These simulations were driven by weather data from 21 SHP weather stations during 2005–2019. Each station-year's simulations were repeated under 54 combinations of wheat planting, termination, and cotton planting dates, 2 soil series with different water capacities, and 10 initial soil moisture conditions. When simulations begin with fall soil moisture at field capacity optimal management options for both soils plant wheat early and cotton late, but have different wheat termination dates. Before cotton planting winter cover crop effects are dominated by reduced surface evaporation and increased transpiration, with greater transpiration effects producing decreased column soil moisture (CSM) at wheat termination. Some soil moisture recharge occurs between termination and cotton planting, but cover crops reduce CSM at cotton planting in both soils in ~75% of simulations. Reduced soil evaporation and soil moisture recovery continues after cotton planting, resulting in positive effects on seed cotton yield in 50% of the silty clay loam simulations and in 67% of the fine sandy loam simulations. Gradually reducing initial fall soil moisture in the silty clay loam reduces wheat biomass but increases the incidence of positive effects on seed cotton yields and CSM at cotton planting and harvest. By contrast, drier initial soil moisture in the fine sandy loam had relatively minor yield and CSM effects. In both soils terminated wheat residue led to increased CSM at cotton harvest in at least 70% of the simulations regardless of soil moisture at wheat planting.

Reconstructing late Miocene depositional environments in the central High Plains, USA: Lithofacies and architectural elements of the Ogallala Formation

The late Miocene Ogallala Formation hosts much of the High Plains aquifer of North America, though it is poorly studied in the central High Plains region where only a small fraction of its total thickness is exposed. One exception is in western Kansas, where up to 40 m of the Ogallala Formation crop out along the bluffs of Ladder Creek Canyon. These deposits consist of stacked and laterally extensive, multistory channel bodies dominated by sandy bedforms with little or no intervening floodplain mudstone. We interpret each ~2–4 m-thick story as a sandstone bed that formed during a single depositional episode and infilled a broad and relatively shallow braided river channel. Each story preserves elements suggesting high discharge conditions, followed by low discharge or the complete abandonment of the river channel after active streamflow either migrated away from the study area or ceased regionally for a relatively long period of time. High discharge conditions are characterized by channel-filling, current-formed transverse bars, gravel-rich longitudinal bars, and sand sheets deposited while the channel was largely flooded and nearly the entire riverbed mobilized. Low discharge conditions are indicated by lens-shaped, trough cross-stratified channels scoured into previously deposited bars. Channel-fill deposits were formed when the remaining flow was confined to one or more narrow streams that braided across the exposed channel belt. Persistent low discharge conditions are suggested by channel-belt-wide subaerial exposure of bar surfaces for a period of time sufficient to promote colonization by soil-burrowing organisms and moderate soil development. Abandonment of the broader channel belt is indicated by advanced calcretization within a story and the presence of aerially restricted and fossiliferous mud-filled channel pools where the final repositories of surface water attracted local paleofauna before infilling or drying completely. The depositional environment of the Ogallala Formation in the study area is most similar to “Platte type” fluvial systems characterized as shallow, perennial, and sand-dominated braided rivers. Comparisons with previously studied localities in the northern and southern High Plains reveal differences in fluvial style, sediment source areas, cut-and-fill geometries, and eolian input.

Attractiveness of Drought-tolerant Plants to Insect Pollinators in the Southern High Plains Region

Urban and rural landscapes are important for providing floral resources to pollinating insects, yet determining the attractiveness of specific plants to a variety of pollinators remains a need in many regions. The objective of this study was to determine the attractiveness of 30 different plants to foraging insects. On 14 dates in 2016 and 2017, floral abundances were measured and the number of insect visitors recorded. A total of 57 insect morphospecies were recorded, with bees (Apoidea: Anthophila) the most abundant pollinator and honey bees the most frequently observed forager. Russian sage (Salvia farinacea) and Catmint (Nepeta × faassenii ‘Walker’s Low’) attracted the greatest number of pollinators. Native plants adapted to the region attracted the highest diversity of pollinators. Thirteen plants, some that are considered good pollinator plants, attracted low numbers of insects. Five pollinator taxa (Anthophora californica/urbana, Apis mellifera, Agapostemon angelicus/texanus, Lasioglossum spp., and Bombyliidae) were attracted to 10 or more different plants, while approximately 65 percent of the taxa were attracted to three or fewer plants. Results support strategies for both grassland restoration and the selection of plants when resources and habitat for pollinators are considered in the management of urban green spaces.

Cropping system diversity and tillage intensity affects wheat productivity in Texas

AbstractWheat (Triticum aestivum L.) production in Texas depends heavily on conventional tillage (CT) and a long summer fallow period, which contributes to soil degradation. This study compared the impact of reducing tillage intensity (CT, no‐tillage, and strip‐tillage) combined with summer cropping to CT–summer fallow on wheat establishment, grain production, and herbage mass from 2016 to 2020 in three Texas ecoregions (Coastal Plains, Southern High Plains, and Blackland Prairie). Tillage and summer cropping resulted in variable impacts on wheat stand establishment, grain yield, and herbage mass across years and locations. At Beeville, in the Coastal Plains, wheat grain and herbage mass yields were not impacted by tillage. Sorghum (Sorghum bicolor [L.] Moench) cropping resulted in less wheat grain yield in 2020. In 1 yr at Lubbock in the Southern High Plains, wheat grain yield was greater with CT than reduced tillage. Sorghum summer cropping resulted in lower wheat grain yield than cover crop mixture or cowpea (Vigna unguiculata [L.] Walp.) in 2017, but yield was greater in 2020. At Thrall, in the Blackland Prairie, wheat stand establishment and yield with reduced tillage were greater than CT in 2016, whereas CT was greater in 2017 and 2020. Sorghum or cover cropping resulted in reduced wheat grain yield compared with fallow in 2018, but sorghum and sesame (Sesamum indicum L.) resulted in increased yield compared with fallow in 2019 and 2020. Summer cropping in wheat production systems rarely had a negative impact on wheat production compared with summer fallow in all three ecoregions.

Employing machine learning to quantify long-term climatological and regulatory impacts on groundwater availability in intensively irrigated regions

The steady overexploitation of the Ogallala Aquifer underlying the U.S. High Plains Region has put irrigated crop production at risk, particularly in the Southern and Central High Plains. To manage this issue properly, a data-driven modeling framework is developed and tested that is fast to employ and yet provides reliable long-term groundwater level (GWL) forecasts as a function of climatological and anthropogenic factors. The modeling framework uses the random forests (RF) technique in combination with ordinary kriging, and is tested in Finney County in southwest Kansas. The introduction of groundwater withdrawal potential as a new surrogate for pumping intensity enables the RF model to capture decline in groundwater depletion rate as the system progresses towards aquifer depletion and/or as a result of well retirement policies. The RF model is executed from 2017 to 2099 for 20 different downscaled global climate models (GCMs) for the two representative concentration pathways (RCP) scenarios of 4.5 and 8.5. The results show the aquifer will cease to support irrigated agriculture in most of the county by 2060 under status quo management and average climate conditions. Moreover, climate will likely shift the aquifer’s depletion time frame by 15 years or less in most of the study area. The long-term combined impact of well retirement plans and climate conditions on groundwater depletion trends imply well retirement policies do not lead to sustained groundwater savings. This study demonstrates the capacity of machine learning models to serve as a rapid assessment tool, informing policymakers about future groundwater availability in intensively irrigated regions and under different climate and management conditions.

Late Quaternary aeolian environments, luminescence chronology and climate change for the Monahans dune field, Winkler County, West Texas, USA

• Thermal transfer luminescence dating indicates Monahans aeolian record spans 550 ka. • Chronostratigraphic analyses identified at least six aeolian depositional periods (ADP). • Prominent ADP occur at 545 to 475, 300 to 260, 70 to 45, and post 16 ka. • A Playa lake deposit dated to 235 to 195 ka identified adjacent to Monahans dune field. • ADPs occur preferential during stadials, when the Laurentide ice is <80 % maximum volume. Dune fields on the Southern High Plains such as the Monahans in West Texas are archives of Quaternary environmental variability. Stratigraphic analyses and sixty-one optically stimulated luminescence (OSL) ages from seven Geoprobe cores and one section from the Monahans reveal a ∼ 550 ka old aeolian sedimentary record with seven carbonate/argillic paleosols and a playa-lake margin deposit. OSL ages on quartz-grains from aeolian sediments by two protocols, single aliquot regeneration (SAR) and thermal transfer (TT), yield congruent ages between 50 and 250 ka, and the oldest ages of ca. 550 ka, potentially minima. This chronostratigraphic analysis and finite-mixture modeling of the OSL-age distribution identify-four aeolian depositional periods (ADP) at 545 to 475, 300 to 260, 70 to 45, and post 16 ka and possibly-two additional ADPs 460 to 420 ka and 350 to 320 ka. Playa lake deposits identified west of the Monahans and correlative to carbonate-rich paleosols indicate that wetter conditions prevailed during interglacial MIS 7, 235 to 195 ka. Another wetter period, 25 to 16 ka, with the formation of Lake King in the adjacent Rio Grande Valley is correlative with a pedogenically-modified <2 m-thick aeolian sand. This study underscores that there may be multiple climatic states, during glacials and interglacials, associated with wetter conditions. In turn, the thickest, preserved aeolian deposits are associated with transitional climate periods, penecontemporaneous with stadials, when the Laurentide ice sheet was <80 % of the last glacial maximum volume, with precipitation-bearing zonal circulation shifted northward and weakened meridional moisture flux.

Trends in Lesser Prairie-Chicken Habitat Extent and Distribution on the Southern High Plains

The lesser prairie-chicken (Tympanuchus pallidicinctus) is a species of prairie grouse that occupies grassland ecosystems in the Southern and Central High Plains of the Great Plains. Reduced abundance and occupied ranges have led to increased conservation efforts throughout the species’ range. Habitat loss is considered the predominant cause of these declines. In the Southern High Plains of Texas and New Mexico, lesser prairie-chicken habitat corresponds to the Sand Shinnery Oak Prairie Ecoregion, which is comprised of a mixture of sand shinnery oak (Quercus havardii)-dominated grasslands, sand sagebrush (Artemisia filifolia)-dominated grasslands, and mixed grasslands. In sand shinnery oak–grassland communities, conversion to row-crop agriculture, continuous unmanaged livestock grazing, restriction of natural fire, invasive plant species (e.g., mesquite (Prosopis spp.)), extensive use of herbicides, energy development, and a variety of other factors have also negatively affected ecosystem extent and function. We integrated historical maps and remote sensing-derived information to measure trends in the extent and geographical distribution of sand shinnery oak prairies in eastern New Mexico and northwest Texas. Potential lesser prairie-chicken habitat was reduced by 56% from a potential of 43,258 km2 to 18,908 km2 in ~115 years (since pre-settlement). Our assessment indicated both mixed grasslands and sand shinnery oak-dominated grasslands were transformed from large parcels of existing vegetation communities to urban settlements, row crops, roads, and industrial land uses by the 1970s. Currently, potential habitat is highly fragmented and restricted to isolated locations in Texas and New Mexico, with an increasing dominance in mixed grasslands, especially in the southeastern portion of the lesser prairie-chicken range. Sand shinnery oak-dominated grasslands have been declining rapidly, from 69% of its potential extent in 1985, 65% in 1995, 54% in 2005, to 42% in 2015. Mixed grasslands drastically declined to 50% of its potential distribution by 1985. Since then, it has been stable until the 2005–2015 period when it declined to 45% of its potential extent. Based on the 2015 assessment, the current potential habitat for lesser prairie-chicken is estimated at 18,908 km2 (1,890,800 ha or 4.6 million acres), where 13,126 km2 corresponds to mixed grasslands and 5782 km2 corresponds to sand shinnery oak-dominated grasslands.

Guar resilience in water‐restricted production

AbstractGuar [Cyamopsis tetragonoloba (L.) Taub] is an alternative crop in the Southern High Plains that thrives in semi‐arid regions, due to its low water input requirements. Field experiments were conducted in 2017 and 2018 at New Deal, TX, to evaluate the response of guar (‘Matador’) to four levels of deficit irrigation (DI; extreme, 51 mm; severe, 127 mm; moderate, 203 mm; and mild, 279 mm). Soil moisture extraction patterns, plant height, leaf area index, yield components, seed yield, harvest index (HI), agronomic water use efficiency (AWUE), and irrigation WUE (IWUE) were measured among the irrigation levels. In both years, guar grown under extreme and severe DI extracted a major portion of the water from the 50‐to‐100‐cm soil depth. Water deficit reduced plant height, leaf area index, and number of pods per plant in both years. However, the IWUE and 1,000‐seed weight increased with reduced irrigation. There were no significant differences in seed yield, HI, and AWUE among treatments as a result of a tradeoff between increased seed weight with low pod production under lower DI treatments and increased pod production with low seed weight under higher DI treatments. Guar extracted water deeper in the soil and produced adequate numbers of pods per plant in balance with the source organ capacity to allocate resources toward optimal seed development. Our research offers valuable information about root exploration and development of larger seeds as compensatory mechanisms that can be further explored to improve the adaptability of guar under water‐restricted production conditions.

Particle size distribution and particulate matter concentrations during synoptic and convective dust events in West Texas

Abstract. Dust events are an important and complex constituent of the atmospheric system that can impact Earth's climate, the environment, and human health. The frequency of dust events in the Southern High Plains of West Texas has increased over the past 2 decades, yet their impact on air quality in this region is still unclear. This is due to the fact that there is only one air quality monitoring station that measures only PM2.5 concentrations (particulate matter with an aerodynamic diameter &lt; 2.5 µm), and there is no information on other PM sizes or the particle size distribution. The Aerosol Research Observation Station (AEROS) unit provides insight into the local variation in particle concentration during different dust events and allows for a better understanding of the impact of dust events on air quality. As this area is prone to dust events, we were wondering if dust events generated by different meteorological causes (synoptic vs. convective) would present similar particle concentrations or particle size distributions. Thus, in this project, three different dust events were measured by AEROS and compared. Each dust event originated from a different direction and lasted a different duration. One of the dust events was synoptic (10 April 2019) and two were convective (5 and 21 June 2019). Measurements of particle mass and number concentration, size distribution, and meteorological conditions for each dust event were compared. The synoptic dust event (on 10 April) was longer (12 h) and had stronger wind speed conditions (up to 22.1 m s−1), whereas the two respective convective dust events on 5 and 21 June lasted only 20 and 30 min and had lower wind speeds (up to 16.5 and 13.4 m s−1). Observation of PM based on daily and hourly values showed an impact on air quality, yet measurements based on daily and hourly values underestimate the impact of the convective dust events. Observations based on a shorter timescale (10 min) reveal the true impact of the two convective dust events. A comparison of the particle size distribution showed that all three dust events presented an increase in particles in the 0.3–10 µm size range. Comparisons of the particle concentration for particles &gt; 5 and &gt; 10 µm show very high values during the dust events. Some particle sizes even increase in concentration by ∼ 2 orders of magnitude compared with the time before the dust event. This leads us to speculate that the impact of convective dust events on air quality in this region is underestimated with the current (hourly basis) method.