Southwestern Kansas Research Articles

Discovery of Paleogene Deposits of the Central High Plains Aquifer In the Western Great Plains, U.S.A.

Abstract: Recent drilling in southwestern Kansas has produced intact cores to investigate the subsurface lithostratigraphy, sedimentary provenance, and chronostratigraphy of strata constituting the central High Plains Aquifer (HPA). In large portions of the HPA, groundwater withdrawals greatly exceed rates of recharge, leading to dramatic water-level declines and growing concerns for long-term sustainability. Two cores, HP1A (98 m) and CMC1 (50 m), are the first and deepest intact cores of the HPA ever collected. The cores show decameter-scale intercalations between suspended-load fluvial deposits composed of fine-grained sands with pedogenically modified overbank deposits, and very coarse-grained sands and gravels consistent with high-energy, bedload-dominated fluvial systems. Six intervals in HP1A and one from CMC1 were analyzed for detrital-zircon U-Pb ages by LA-ICP-MS. The HP1A samples show maximum depositional ages (MDAs) ranging from ∼ 27.5 to 36.4 Ma with depth. A MDA of ∼ 30 Ma was measured in the CMC1 core. These Paleogene zircons likely originated from explosive volcanism associated with the mid-Cenozoic ignimbrite flare-up (44–18 Ma), which blanketed much of western North America with high-volume air-fall tuffs. We propose that a large evaporite-dissolution basin in southwestern Kansas provided the accommodation space to preserve a record of Paleogene strata. The lack of younger middle–late Miocene zircons from cores in southwestern Kansas is striking given that such grains, likely derived from the Snake River Plain–Yellowstone hotspot volcanic provinces (16.1–0.6 Ma), are readily identified in the Ogallala Formation in north-central Kansas and Nebraska. The MDAs suggest Eocene to Oligocene age deposits that are time-equivalent to the Arikaree and White River groups in Nebraska are also present in Kansas.

Calculation of CO2 Storage Capacity for Arbuckle Group in Southern Kansas: Implications for a Seismically Active Region

The total simulated P50 capacity of the 10 sites is 780 million tonnes of supercritical CO2, with some sites, such as Cutter Field in South Western Kansas, providing very low storage capacity (∼ 1 M tonnes) and others, such as Dexter Field in South central Kansas, providing 121 M tonnes of CO2 storage. Most sites with the exception of Cutter Field could be considered as commercial scale CO2 storage reservoirs from a perspective of available pore space. However, the recent increase in earthquakes in South Central Kansas associated with large volume brine disposal could potentially challenge this assessment.

First report of rodents from the late Hemphillian (late Miocene) Zwiebel Channel and a revised late Neogene biostratigraphy/biochronology of the Sand Draw area of Nebraska

A new late Hemphillian (late Miocene) rodent assemblage is reported from Zwiebel Channel, a channel cut into underlying Ash Hollow Miocene sediments along Sand Draw, Brown County, Nebraska. This locality extends the temporal range of rodent history in the Sand Draw area. A new biostratigraphic hypothesis proposes that previously described assemblages with Ogmodontomys are older than those with Ophiomys, as is the case in the Meade Basin of southwestern Kansas. Consequently, two Pliocene temporal zones are recognised. Based on a phylogenetic analysis of Ophiomys, rodent biostratigraphy, and paleomagnetic profiles, Sand Draw assemblages with Ogmodontomys are considered to have been deposited about 3.0–2.8 Ma, while those with Ophiomys were laid down between about 2.8–2.5 Ma. The 1.6 Ma date previously suggested for Ophiomys parvus from Froman Ferry, Idaho is probably too young; it is more likely that O. parvus became extinct in Idaho prior to the North American Microtus immigration event at about 2.0 Ma, inhabiting the Snake River basin until around 2.2 Ma.

Effects of Tamarix removal on the community dynamics of riparian birds in a semiarid grassland

AbstractInvasion of riparian habitats by non‐native plants is a global problem that requires an understanding of community‐level responses by native plants and animals. In the Great Plains, resource managers have initiated efforts to control the eastward incursion of Tamarix as a non‐native bottomland plant (Tamarix ramosissima) along the Cimarron River in southwestern Kansas, United States. To understand how native avifauna interact with non‐native plants, we studied the effects of Tamarix removal on riparian bird communities. We compared avian site occupancy of three foraging guilds, abundance of four nesting guilds, and assessed community dynamics with dynamic, multiseason occupancy models across three replicated treatments. Community parameters were estimated for Tamarix‐dominated sites (untreated), Tamarix‐removal sites (treated), and reference sites with native cottonwood sites (Populus deltoides). Estimates of initial occupancy (ψ2006) for the ground‐to‐shrub foraging guild tended to be highest at Tamarix‐dominated sites, while initial occupancy of the upper‐canopy foraging and mid‐canopy foraging guilds were highest in the treated and reference sites, respectively. Estimates of relative abundance for four nesting guilds indicated that the reference habitat supported the highest relative abundance of birds overall, although the untreated habitat had higher abundance of shrub‐nesters than treated or reference habitats. Riparian sites where invasive Tamarix is dominant in the Great Plains can provide nesting habitat for some native bird species, with avian abundance and diversity that are comparable to remnant riparian sites with native vegetation. Moreover, presence of some native vegetation in Tamarix‐dominated and Tamarix‐removal sites may increase abundance of riparian birds such as cavity‐nesters. Overall, our study demonstrates that Tamarix may substitute for native flora in providing nesting habitat for riparian birds at the eastern edge of its North American range.

Extinction rates of the Meade Basin rodents: application to current biodiversity losses

Extinction rates for terrestrial rodent species from palaeontological sites in the Meade Basin of southwestern Kansas and an archaeological site in New Mexico are compared with extinction rates for modern rodents from locations affected by anthropogenic activities. Background extinction rates are defined as global extinctions occurring over proscribed intervals in the absence of significant environmental perturbations. Background rates for the Meade Basin are estimated at 0–~1.0 E/MSY (extinctions per million species years). Elevated rates from 1.4 to 6.25 E/MSY are associated with volcanic events and Late Pleistocene environmental change. These rates are considerably less than those for rodent extinction rates promoted by human activities during the Holocene, the latter ranging from 42.3 to 50,000 E/MSY.

Land’s complex role in climate change

To mitigate climate change at local, regional, and global scales, we must begin to think beyond greenhouse gases.

Kansas Windscape - 2016 Status

Kansas has played a significant role for the growth of wind energy in the United States. Kansas ranks sixth among states for wind-energy capacity, and is third in the nation for per-capita production of electricity from the wind. Wind farms are sited in topographically high positions on uplands, drainage divides, escarpments, and other rural sites in which there are few or no obstacles to interrupt near-surface wind flow. The best regions of the state include the High Plains, especially in southwestern Kansas, the Blue Hills and Flint Hills, and on the Missouri-Arkansas drainage divide in the Osage Cuestas. Rapid development of wind energy has taken place in these regions during the past few years, except for the Flint Hills, which is an exclusion zone for new wind farms. Bird and bat mortality remains an issue, but with appropriate wildlife mitigation much more wind energy could be developed in Kansas. Aesthetic issues include visibility and noise. Developing safe and renewable energy resources that have...

Evaluating deficit irrigation management strategies for grain sorghum using AquaCrop

Many wells in the US Central Plains can no longer meet full crop water requirements due to declines in Ogallala aquifer water levels. A study was conducted in Southwest Kansas to determine optimum limited irrigation strategies for grain sorghum. Objectives were to (1) calibrate and validate the AquaCrop model, (2) apply AquaCrop to assess the effect of varying climate, planting dates, and soil types on yield, and (3) evaluate water productivities and optimal irrigation needs. Experimental data of grain sorghum were used to calibrate and validate AquaCrop. Planting date was found to substantially affect biomass and grain yield, and hence, considerably affect water productivities. The highest grain water productivities were obtained with late planting in a wet season. Late planting was associated with lower irrigation requirements. Depending on local conditions, we recommend planting to occur between June 1st and June 10th. Grain sorghum yield was optimized on sandy soils of southwestern Kansas with irrigation of 100–275 mm for early, 150–275 mm for normal and 100–275 mm for late planting. The optimal irrigation on silt loam soils for the corresponding planting dates were 175–350, 175–250 and 125–250 mm, respectively, with the lowest and highest in the range being for the wet and dry climate season conditions. Fluctuations in grain sorghum prices had a substantial impact on economic water productivity. Overall planting grain sorghum under optimum conditions combined with deficit irrigation improved water productivity.

Stratigraphy, morphology, and geochemistry of late Quaternary buried soils on the High Plains of southwestern Kansas, USA

This study investigated two stratigraphic sequences that record the complex interplay of sedimentation and pedogenesis over the past ca. 84ka on the High Plains of southwestern Kansas. Up to eight eolian sand and loess units with associated soils were identified in two cores collected from an upland setting. Soil morphological and geochemical data were used to quantitatively assess and compare soil development between multiple buried soils. Chronostratigraphic relationships indicate that 1) loess and eolian sands were episodically deposited during late Marine Isotope Stage (MIS) 5 (ca. 84–70ka), 2) the Sangamon soil at this site formed between MIS 3/4 (ca. 70–52ka), which is consistent with age estimates for renewed Sangamon pedogenesis in the Mississippi River valley, and 3) soil development in the Gilman Canyon Formation began at ca. 44ka and continued until at least 29.2ka. Multiple lines of evidence, including grain-size distributions, structure, clay content, and chemical weathering index data, indicate that the morphology and chemistry of the Ak horizon developed in the Gilman Canyon Formation is a product of cumulization by slow loess additions. Similar evidence suggests that cumulization processes are also responsible for the morphology and chemistry of other buried soils in the stratigraphic sequence. Overall, loess inputs during pedogenesis complicate the quantification of weathering processes in these soils.

Geomys tyrioni, a new species of early Pleistocene dwarf pocket gopher from the Meade Basin of southwestern Kansas

A new early Pleistocene dwarf pocket gopher species is described from the Short Haul, Aries A, and Nash 72 assemblages in the Borchers Badlands of Meade County, Kansas. Geomys tyrioni is defined by its diminutive size and modern dental and mandibular masseter muscle configuration. G. tyrioni , currently known from the interval of about 2.0–1.70 millions of years ago (Ma), replaced the larger G. floralindae and G. quinni of the slightly earlier (2.11 Ma) Borchers assemblage. Mandibular and dental characters place G. tyrioni in the group of Geomys including the extant Great Plains G. bursarius . Within about 24,000 years after the Nash 72 assemblage, G. tyrioni was replaced by modern-sized Geomys cf. G. bursarius in the Rick Forester assemblage, the earliest record of the extant plains pocket gopher in the Meade Basin and North America. G. tobinensis Hibbard is synonymized with G. bursarius . An evolutionary scenario is provided for the Meade Basin geomyines based on current information, and it is suggested that ashfalls may have played a significant role in geomyine cladogenesis and turnover.

Evidence of Field-Evolved Resistance to Bifenthrin in Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) Populations in Western Nebraska and Kansas.

Pyrethroid insecticides have been used to control larvae or adults of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, a key pest of field corn in the United States. In response to reports of reduced efficacy of pyrethroids in WCR management programs in southwestern areas of Nebraska and Kansas the present research was designed to establish a baseline of susceptibility to the pyrethroid insecticide, bifenthrin, using susceptible laboratory populations and to compare this baseline with susceptibility of field populations. Concentration-response bioassays were performed to estimate the baseline susceptibility. From the baseline data, a diagnostic concentration (LC99) was determined and used to test adults of both laboratory and field populations. Larval susceptibility was also tested using both laboratory and field populations. Significant differences were recorded in adult and larval susceptibility among WCR field and laboratory populations. The highest LC50 for WCR adults was observed in populations from Keith 2 and Chase Counties, NE, with LC50s of 2.2 and 1.38 μg/vial, respectively, and Finney County 1, KS, with 1.43 μg/vial, as compared to a laboratory non-diapause population (0.24 μg/vial). For larvae, significant differences between WCR field and laboratory populations were also recorded. Significant differences in mortalities at the diagnostic bifenthrin concentration (LC99) were observed among WCR adult populations with western Corn Belt populations exhibiting lower susceptibility to bifenthrin, especially in southwestern Nebraska and southwestern Kansas. This study provides evidence that resistance to bifenthrin is evolving in field populations that have been exposed for multiple years to pyrethroid insecticides. Implications to sustainable rootworm management are discussed.

Underpressure in Mesozoic and Paleozoic rock units in the Midcontinent of the United States

Potentiometric surfaces for Paleozoic strata, based on water well levels and selected drill-stem tests, reveal the control on hydraulic head exerted by outcrops in eastern Kansas and Oklahoma. From outcrop in the east, the westward climb of hydraulic head is much less than that of the land surface, with heads falling so far below land surface that the pressure:depth ratio in eastern Colorado is less than 5.7 kPa/m (0.25 psi/ft). Permian evaporites separate the Paleozoic hydrogeologic units from a Lower Cretaceous (Dakota Group) aquifer, and a highly saline brine plume pervading Paleozoic units in central Kansas and Oklahoma is attributed to dissolution of Permian halite. Underpressure also exists in the Lower Cretaceous hydrogeologic unit in the Denver Basin, which is hydrologically separate from the Paleozoic units. The data used to construct the seven potentiometric surfaces were also used to construct seven maps of pressure:depth ratio. These latter maps are a function of the differences among hydraulic head, land-surface elevation, and formation elevation. As a consequence, maps of pressure:depth ratio reflect the interplay of three topologies that evolved independently with time. As underpressure developed, gas migrated in response to the changing pressure regime, most notably filling the Hugoton gas field in southwestern Kansas. The timing of underpressure development was determined by the timing of outcrop exposure and tilting of the Great Plains. Explorationists in western Kansas and eastern Colorado should not be surprised if a reservoir is underpressured; rather, they should be surprised if it is not.

Forces driving late Pleistocene (ca. 77–12 ka) landscape evolution in the Cimarron River valley, southwestern Kansas

This study presents stratigraphic, geomorphic, and paleoenvironmental (δ13C) data that provide insight into the late Pleistocene landscape evolution of the Cimarron River valley in the High Plains of southwestern Kansas. Two distinct valley fills (T-1 and T-2) were investigated. Three soils occur in the T-2 fill and five in the T-1 fill, all indicating periods of landscape stability or slow sedimentation. Of particular interest are two cumulic soils dating to ca. 48–28 and 13–12.5 ka. δ13C values are consistent with regional paleoenvironmental proxy data that indicate the prevalence of warm, dry conditions at these times. The Cimarron River is interpreted to have responded to these climatic changes and to local base level control. Specifically, aggradation occurred during cool, wet periods and slow sedimentation with cumulic soil formation occurred under warmer, drier climates. Significant valley incision (~25 m) by ca. 28 ka likely resulted from a lowering of local base level caused by deep-seated dissolution of Permian evaporite deposits.

Kochia Suppression with Cover Crops in Southwestern Kansas

Kochia (Kochia scoparia L.) is a well‐adapted weed found throughout the semiarid Great Plains and has increased in concern because biotypes with resistance to numerous herbicide modes of action are present, thus reducing options for control. The objectives of the research were to determine if cover crops growing during the fallow phase of a no‐till winter wheat (Triticum aestivum L.)–fallow cropping system could reduce kochia density and biomass without reducing subsequent winter wheat yields. Five fall‐sown cover crops of Austrian winter pea (Pisum sativum ssp. arvense), hairy vetch (Vicia villosa Roth.), winter triticale (Triticale hexaploide Lart.), and mixtures of Austrian winter pea‐winter triticale and hairy vetch‐winter triticale were evaluated and compared with chemical fallow and to five spring‐sown cover crops of spring lentil (Lens culinaris Medik.), spring pea (Pisum sativum L.), spring triticale, and mixtures of spring lentil‐spring triticale and spring pea‐spring triticale. Fall‐sown triticale alone or in mixture reduced kochia density by 78 to 94% and reduced kochia biomass by 98% compared with kochia in chemical fallow. Spring‐sown cover crops and kochia emerged together in early March; thus kochia density and biomass were not affected by these cover crops. Fall‐sown cover crops that produced more biomass were most effective at suppressing kochia density and biomass. All cover crops were terminated by either forage harvest or chemical application by June 1. Subsequent winter wheat yields varied by cover crop across years, and in general winter wheat after cover crops yielded comparable to or less than chemical fallow.

Subterranean Red by Kathleen Johnson (review)

Reviewed by: Subterranean Red by Kathleen Johnson Elizabeth Toombs Subterranean Red. By Kathleen Johnson. Norman, OK: Mongrel Empire Press, 2012. 61 pages, $14.00. The poetry of Kathleen Johnson, a native Oklahoman of Cherokee and Scots-Irish ancestry, grasps onto snapshots of generational memory and rhythms of imagination to explore roots and home. Red earth, the central element of Johnson’s second poetry collection, Subterranean Red, underscores the connection of identity with the color of creative passion, place, and people. Some selected poems and characteristics from Johnson’s first poetry book, Burn, a 2009 Kansas Notable Book, continue to emit textual light in this collection. At times, the characters in “Mixed Blood Messages,” the first of two sections in Subterranean Red, struggle in balancing light as a generative force with the darkness of unknowing. Many poems in this section end in darkness where characters often “look to the shadows” (6). “In Wildwood Cemetery” illustrates a desire for knowledge from ancestors who literally have returned to the earth: “tonight we share / the same November moonlight, / but we’re both still in the dark” (13). This section closes with a Cherokee legend, “Raven Mocker,” an extreme expression of darkness where a witch and “harbinger of fear and final dark” steals away the heart of the dying to extend her own life (17). Photographs often drive the narratives of these poems and serve as entryways to memory reinforced by language. Here, relationships to kin and land serve as sources of survival and strength. For example, “Cherokee Grandfather” adds dimension to the past that creatively informs the present and serves as a guide for the future. However, the most lasting and impressionable relationships are not captured visually. “Wild Sand Plums” recalls songs in the “old language” about faith and survival traced back to Cherokee homelands in Georgia and shared through four generations of women (9). These ancestral lives remind [End Page 479] us about the importance of one’s relationship between physical and spiritual worlds. Earth also looms in the second section, “Cimarron Breaks,” named for an ecoregion in southwestern Kansas that extends into central Oklahoma. The breaks reference the broken ground where Johnson’s great-great-grandfather, the poet known as the Pilgrim Bard, homesteaded. These breaks may also express the ruptures in Johnson’s family, such as her father’s alcoholism and infidelity, the destructive capacity of landscape noted in “Dust Bowl Diary, 1935” and “Tornado Warning,” or the cultural scarring and subsequent development that resulted from the Cherokee Strip Land Run in 1893. Rather than dwelling on these conflicts, however, Johnson continually stresses the importance of language as a source of regeneration: “But because we have your words, the wonder holds. / Nothing, not even prairie cyclones, can whisk it all away” (26). Through vivid imagery, heavy symbolism, and skillful form, Johnson offers an appreciation of issues related to mixed-blood identity that defies neat categorization. Even though Subterranean Red is anchored to earth, Johnson’s impressions of the Oklahoma landscape through poetry reveal a sense of home that denies fossilization. She artfully engages in a homecoming of the imagination, a dynamic spiritual process that grows from a sense of connection. Elizabeth Toombs University of Oklahoma Copyright © 2014 Western Literature Association

Evaluation with Dynamic Simulations of the Volumetric Curvature Tool for Modelling Reservoir Compartments and Leakage Pathways in the Arbuckle Saline Aquifer

Abstract The Arbuckle saline aquifer in southwestern Kansas, a siliceous dolomite with interbedded shales, is an ideal candidate for CO 2 sequestration because of thickness (600–1000 ft), supercritical depth (>3500 ft), stratigraphic isolation from freshwater aquifers, and very limited oil and gas production. The Arbuckle Group (Cambro-Ordovician) consists dominantly of shallow shelf carbonates overprinted by karstic features, such as paleokarst compartments and associated fracture systems, developed during repeated subaerial exposure. Volumetric curvature (VC) tool improves identification and numerical characterization of karst features in seismic volume. This paper discusses how seismic and well data were integrated into a geocellular model, and a discrete fracture model and dynamic numerical simulation of CO 2 injection.

Patterns of size change in late Neogene pocket gophers from the Meade Basin of Kansas and Oklahoma

A dense late Neogene history of pocket gophers from the Meade Basin of south-western Kansas and north-western Oklahoma preserves a detailed record of size change, as indicated by mean length of the lower fourth premolar. A ‘time for space substitution’ interpretation results in the tentative recognition of a pattern analogous to character displacement, in which the small to medium-sized Pliogeomys buisi, P. louderbachi, Geomys minor and G. floralindae are considered ecological analogues and treated as a single ecological entity, Avatar A. The larger G. jacobi and G. quinni are combined as Avatar B. Statistical analyses confirm that populations of Avatar A are of equal size when allochronic from Avatar B, and significantly smaller when synchronic (and sympatric) with Avatar B. However, this pattern is complicated by the observation that Avatar A began dwarfing before the appearance of Avatar B. This historical perspective suggests that static size patterns among modern taxa may have a complex history. Occasional diminutive geomyid transients (G. adamsi, Thomomys cf talpoides) are always paired with significantly larger, medium-sized Geomys. Although a random walk explanation for the pattern of size changes is unlikely, we are currently unable to distinguish between environmental change and competition as the likely forcing mechanisms.

Relationships between Height, Diameter, and Crown for Eastern Cottonwood (<I>Populus Deltoides</I>) in a Great Plains Riparian Ecosystem

Models were developed for tree height and crown characteristics of eastern cottonwood (Populus deltoides Bartr. Ex. Marsh). Equations related cottonwood height to dbh and crown condition category (less than 50% live, at least 50% but less than 100% live, and 100% live). Crown width equations related crown width to dbh, crown condition category, and basal area per hectare. Additional equations related crown length to total height, basal area per hectare, and crown condition category. Data were obtained during a sample of trees located in a riparian area surrounding the Cimarron River on the Cimarron National Grassland. The band of trees on either side of the Cimarron River channel was surrounded by treeless, semiarid grassland typical of southwestern Kansas. Many trees were growing in scattered clumps or nearly open grown. In addition, there was variability in proportions of live crown present, as classified by crown condition category. These factors influence crown dimensions and are typical of cottonwood trees found in Great Plains riparian areas. Since height measurement trees were sampled on plots, mixed-effects models with random effects representing plot effects were developed for the height-diameter relationships (a model developed using ordinary least squares is also presented). Models of crown width and crown length were developed using ordinary least squares.

Identification of “ever-cropped” land (1984–2010) using Landsat annual maximum NDVI image composites: Southwestern Kansas case study

A time series of 230 intra- and inter-annual Landsat Thematic Mapper images was used to identify land that was ever cropped during the years 1984 through 2010 for a five county region in southwestern Kansas. Annual maximum Normalized Difference Vegetation Index (NDVI) image composites (NDVIann-max) were used to evaluate the inter-annual dynamics of cropped and non-cropped land. Three feature images were derived from the 27-year NDVIann-max image time series and used in the classification: 1) maximum NDVI value that occurred over the entire 27year time span (NDVImax), 2) standard deviation of the annual maximum NDVI values for all years (NDVIsd), and 3) standard deviation of the annual maximum NDVI values for years 1984–1986 (NDVIsd84–86) to improve Conservation Reserve Program land discrimination.Results of the classification were compared to three reference data sets: County-level USDA Census records (1982–2007) and two digital land cover maps (Kansas 2005 and USGS Trends Program maps (1986–2000)). Area of ever-cropped land for the five counties was on average 11.8% higher than the area estimated from Census records. Overall agreement between the ever-cropped land map and the 2005 Kansas map was 91.9% and 97.2% for the Trends maps. Converting the intra-annual Landsat data set to a single annual maximum NDVI image composite considerably reduced the data set size, eliminated clouds and cloud-shadow affects, yet maintained information important for discriminating cropped land. Our results suggest that Landsat annual maximum NDVI image composites will be useful for characterizing land use and land cover change for many applications.

Relationships between feedlot health, average daily gain, and carcass traits of Angus steers

<h2>ABSTRACT</h2> Angus steers (n = 17,919) fed at a single feedlot in southwestern Kansas between 1997 and 2007 were used to evaluate the relationships between feedlot health, ADG, and carcass traits. Cattle were not commingled and were predominantly preconditioned and backgrounded before shipment to the feedlot. Morbidity decreased and ADG increased with increasing initial BW (P < 0.01); percentage Choice was related (linear P=0.02) to arrival BW in steers that were not treated for disease, but with only 2.8% units separating the least (<295 kg) and the greatest percentage Choice groups (375–409 kg). There were linear and quadratic decreases in ADG, final BW, HCW, QG, and YG with increased number of times treated (P < 0.02). With decreasing QG there were linear and quadratic decreases in ADG, final BW, HCW, and YG. Increasing YG from YG 1 and 2 to YG 3 increased percentage Choice by 16.1 points, and there was an additional 1.6-point increase moving to YG 4 and 5 (linear and quadratic, P < 0.01). Average daily gain was very similar among cattle that graded Prime, Choice, and Select, suggesting that performance and QG are not genetically linked; instead, much of the difference in QG can be explained by differences in YG.