Rolling Plains Of Texas Research Articles

Regenerative Practices Show Promise in Dryland Cotton Systems

AbstractRegenerative practices, such as no‐till and cover crops, are advocated for their positive impacts on soil health and the environment. Nevertheless, there are challenges associated with implementing these practices. The objective of this simulation study was to assess the potential for soil carbon sequestration, soil water storage, and cotton yield response when implementing regenerative practices in the water‐limited environment of the Texas Rolling Plains region. Earn 1 CEU in Sustainability by reading this article and taking the quiz.

Teff grass increases summer forage availability in the Rolling Plains of Texas

AbstractTeff [Eragrostis tef (Zucc.) Trotter] grass has gained popularity in the United States as an emergency summer forage for livestock due to its drought tolerance and rapid growth habit. An alternative forage would benefit Texas Rolling Plains growers due to the summer forage shortage caused by drought conditions. However, among the teff research conducted in the United States, there is great variability in the forage yields and nutritive values depending on the amount of nitrogen and available water. The objective of the study was to evaluate forage productivity and nutritive value of teff in the Texas Rolling Plains under irrigated and dryland conditions with two nitrogen rates and application timings. Nitrogen fertilizer treatments included single applications of either 50 or 100 lb a−1 applied at planting and a split application of either 50 or 100 lb a−1 applied both at planting and after the first harvest. No differences were observed among nitrogen rates and application methods in the irrigated trial (5286 lb a−1). The split application of 100 lb a−1 produced the greatest total yield in the dryland trial (3096 lb a−1) with no yield advantage of 100 lb N a−1 over 50 lb N a−1 at the first cutting. Forage nutritive values were similar to the warm‐season forage species utilized in the region. This study showed that teff can be an alternative forage species in the region. Future research will include planting dates, nitrogen application timing, cutting height, and the interaction of these factors on yield and nutritive values of teff.

EXPLORING A PLANT-DIVERSITY HYPOTHESIS TO EXPLAIN HELMINTH PREVALENCE IN NORTHERN BOBWHITE (COLINUS VIRGINIANUS) IN TEXAS, USA.

Helminths, in particular eyeworms (Oxyspirura petrowi) and cecal worms (Aulonocephalus pennula), may be a factor influencing northern bobwhite (Colinus virginianus) populations in Texas. Previous research has shown a discrepancy in helminth infections between the Rolling Plains and Rio Grande Plains of Texas, US, potentially caused by differences in intermediate host distribution and abundance. We explored an alternative hypothesis centered on plant diversity, given that many plants possess phytochemicals with anthelmintic properties. We predicted that plant diversity would be greater and bobwhite diet more diverse in the Rio Grande Plains than the Rolling Plains, which in turn would potentially expose bobwhites to more plants with anthelmintic properties and therefore result in lower parasite prevalence and intensity. We conducted a literature review of plant diversity, anthelmintic plants, and bobwhite diet in Texas to explore this hypothesis. We also quantified the relationship between helminth prevalence in bobwhites and latitude. We documented trends for higher plant species richness, greater number of anthelmintic plants, and more diverse bobwhite diet in the Rio Grande Plains compared to the Rolling Plains. In addition, we documented a trend for increasing helminth prevalence with latitude for eyeworms but not cecal worms. Our study provides circumstantial evidence supporting the plant-diversity hypothesis and warrants experimental testing.

Development and evaluation of a decision support mobile application for cotton irrigation management

Irrigation decision support tools are a means by which crop producers can improve the efficiency of water they apply. However, the available tools generally have poor adoption rates due to high costs, requirement for technical background and skills, need for extensive input data, lack of economic analysis support, and/or low accuracy. Here, we aimed to develop an inexpensive and easy-to-use decision support mobile app called Irrigation Decision-support for Conserving Resources and Optimizing Production (idCROP), to aide cotton producers in the Texas Rolling Plains and High Plains regions to increase water-use efficiency while maintaining higher crop yields. The app was built based on the crop simulation model, Decision Support System for Agrotechnology Transfer (DSSAT), and a newly developed economic model to provide real-time irrigation schedules and projected economic outcomes based on water use and production goals. The app integrates real-time management information from users with historic, real-time, and forecasted short-term and seasonal weather data. This integration enables output of efficient and situationally relevant irrigation schedules and forecasts of associated cotton yield and economic returns. This enables users to choose an irrigation strategy that best suits their irrigation capacities and expected returns. The irrigation schedules can be improved by optional remote detection of plant water stress using a sensor platform mounted on a pivot irrigation system, but the app can be used without the sensors in conjunction with any type of irrigation system. The crop model-based irrigation scheduling in idCROP was validated at the Texas A&M AgriLife Chillicothe Research Station in the Texas Rolling Plains region and acceptable results were obtained. The idCROP app provides producers with a simple but powerful tool that takes the guess work out of irrigation management, helping them apply limited irrigation water more efficiently.

Winter cover crop impact on soil health in Texas Rolling Plains dryland cotton

AbstractThe Rolling Plains of Texas are historically semi‐arid with sporadic, high intensity storms followed by periods of long drought. Fallow management is a common practice intended to store soil water, but leaves the bare soil exposed to erosive forces that can diminish the soil productivity. Cover crops in no‐till (NT) agriculture have been proposed to increase soil health under environments with low precipitation as an alternative to fallow management. This study evaluated multiple treatments in a dryland cotton system including: (1) conventional tillage (CT); (2) NT; and NT with the following cover crops: (3) wheat; (4) Austrian winter pea; (5) crimson clover; (6) hairy vetch; and (7) mixed species cover. Soil samples were collected at 0, 3, and 6 weeks after cover crop termination and analyzed for soil organic carbon, total nitrogen, inorganic N, water‐extractable organic carbon, water‐extractable organic nitrogen, carbon mineralization, and phospholipid fatty acid analysis. For all parameters tested, there was no significant difference between CT and NT at any date or depth, so the addition of cover crops to NT cotton systems might be needed in order to enhance NT in regard to soil function. The multi‐species mixed treatment was predicted to perform the best out of the cover crop treatments due to its combined benefits from grasses and legumes. However, the single‐species Austrian winter pea treatment had 24% and 28% higher soil carbon and nitrogen than no‐till without a cover crop, and can be a useful alternative to fallow management under these dryland agriculture conditions.

Influence of cropland on resource selection by pronghorn

AbstractPronghorn (Antilocapra americana) are a grassland specialist that have experienced a >60% reduction in their historical range due to habitat fragmentation and encroachment of woody vegetation. Pronghorn populations are increasing in the Texas Panhandle despite conversion of grassland to cropland (27–43% of the regional landscape) and associated fragmentation. We hypothesized that pronghorn avoid cropland when selecting seasonal home ranges and avoid cropland within their home ranges. We captured 64 adult pronghorn of equal sex ratios in both the High Plains (n = 32) and Rolling Plains (n = 32) ecoregions of Texas, USA, during February 2017 and fitted them with iridium satellite global positioning system (GPS) collars. We collared 27 additional pronghorn in 2018 to account for mortalities and collar failures. We estimated resource selection functions for the High Plains and Rolling Plains populations using mixed‐effects logistic regression at the home range (second order) and within home range (third order) scales separately for each ecoregion and season (fawning, summer, rut, and winter). Our hypothesis that pronghorn avoid cropland was supported in the Rolling Plains ecoregion at the home range scale; otherwise, cropland was inconsistently and seasonally important in resource selection. Furthermore, pronghorn often avoided paved roads more strongly than cropland. At the home range scale during 2017–2019, female pronghorn in the High Plains selected cropland during rut and winter. Males exhibited weak selection for cropland during rut. Within home ranges in the High Plains, female pronghorn avoided cropland during fawning in 2017, during rut in 2017 and 2018, and during winter 2019 but selected areas closer to cropland in winter 2017 and fawning 2018. Males selected areas farther from cropland during all sampling dates in 2017 and winter 2019. Avoidance and selection of cropland within home ranges also varied among seasons and years in the Rolling Plains. Overall, pronghorn avoided cropland when selecting home ranges in the Rolling Plains and cropland was otherwise inconsistently and only seasonally important in resource selection at the home range and within home range scales. We speculate that loss of pronghorn habitat to cropland in the High Plains and Rolling Plains of Texas may outweigh temporary nutritional benefits from seasonal use of crops.

Water quality effects of cover crop, grazing and tillage implementation in a long-term no-till wheat system

Agricultural anthropogenic nitrogen (N) and phosphorus (P) continue to be major surface and subsurface water pollutants in developed countries. Integrated crop-livestock systems in the semi-arid Texas Rolling Plains are characterized by continuously cultivated monoculture combined with grazing. Improperly managed grazing can increase soil compaction, and subsequently, decrease infiltration, which leaves the soil exposed to erosion. Grazing is therefore of paramount importance to water quality. Cover crop (CC) use improves soil ecosystem services and functions. The objective of the current study was to characterize soil water quality following CC under continuous wheat (Triticum aestivum), grazing, tillage, and no-till practices under a typic Haplustepts, Rotan clay loam soil type. Treatments evaluated include 1) conventional tillage without a CC (CT); 2) no-till without a CC (NT); 3) no-till with a CC (NTC); and 4) no-till with a grazed CC (NTCG). Portable rainfall simulators were used to assess surface runoff water quantity and quality after CC implementation in a long-term no-till continuous wheat system. Cover crop treatments, both grazed and un-grazed, reduced the amount of runoff by 4–6 times compared to no CC treatments (NT and CT). Converting 12-year-old NT to CT reduced infiltration by at least 43 % and increased runoff by 58 % compared to long-term NT. Consequently, total solids load and concentration for CT were 4–14 times greater than all NT treatments (NT, NTC, NTCG). Conventional tillage (CT) also increased total P loads and concentrations by 2–11-fold compared to all NT treatments (p < 0.05). Rainfall events occurring within three weeks after CC termination resulted in about 6 times greater soluble reactive P (SRP) (except NTCG) and about 2–3 times greater dissolved organic C (DOC) concentrations from CC treatments than non-CC treatments, although this was not observed for subsequent runoff events. Tilling the soil had more deleterious effects compared to flash grazing CC. Adopting NT, either alone, or long-term in combination with CC (either flash grazed or un-grazed) are potentially sustainable viable practices in semiarid regions that can reduce environmental contamination.

Modeling the impacts of cover crops and no-tillage on soil health and cotton yield in an irrigated cropping system of the Texas Rolling Plains

An interest to grow cover crops is increasing in the semi-arid Texas Rolling Plains (TRP) region, where cotton ( Gossypium hirsutum L.) is a major cultivated crop. Under conservation tillage systems, cover crops are expected to enhance ecosystem services, including improved soil health and erosion reduction. However, there is a concern that cover crops could deplete soil water content and affect the subsequent cotton production. This study evaluated the efficacy of growing winter cover crops in a continuous cotton production system under irrigated conditions at Chillicothe, TX with the Denitrification Decomposition (DNDC) model. Treatments included: conventional tillage (CT), no-till (NT), no-till with mixed-species cover crop (Mixture), and no-till with winter wheat ( Triticum aestivum ) cover crop (Wheat) . The DNDC model was calibrated and validated against observed data from 2012 to 2020. Seed cotton yield prediction during model calibration had a percent bias (PBIAS) of 4.4 %, root mean square error (RMSE) of 385 kg ha −1 , r 2 of 0.55, d-index of 0.84, and a Nash–Sutcliffe model efficiency (NSE) of 0.92. Seed cotton yield during model validation had PBIAS of − 2.0 %, RMSE of 279 kg ha −1 , r 2 of 0.75, d-index of 0.93, and a NSE of 0.72. Simulated soil organic carbon (SOC) stock had a PBIAS of 8.6 % and 3 %, RMSE of 1.8 and 0.74 Mg ha −1 , r 2 of 0.92 and 0.98, d-index of 0.97 and 0.99, a NSE of 0.89 and 0.98 during model calibration and validation, respectively. Daily trends of simulated soil water content at 0–100 cm depth were within the acceptable range. Long-term simulations (25 years) revealed: (1) planting cover crops could accrue 11–19 % more SOC and 4–14 % more TN compared to no-cover crops, (2) cotton yield under cover crops was not significantly different from that under no-cover crops, (3) cover crop biomass increased immoblisation of nitrogen (N), which led to a decline in available N and hence, N-stress was simulated during the initial cotton growth period. In nutshell, results showed the potential of conservation management systems such as no-till and cover crops in improving soil health indicators without affecting cotton yields. • Simulated effect of mixture and winter wheat cover crops on seed cotton yield was not significant. • Cover crops sequestered 11–19 % more soil organic carbon (SOC) compared to no-cover crops. • Cover crops accrued 4–14 % more total nitrogen (TN) compared to no-cover crops. • Rate of SOC and TN accrual was highest under mixed species cover crop followed by winter wheat. • Soil N availability was declined in early stages of cotton due to increased N immobilization by cover crop biomass.

Quail and rain in semiarid rangelands: Does management matter?

AbstractRainfall is a strong driver of quail populations on southwestern rangelands and can account for a large portion (~70–95%) of the variability in regional quail production and abundance. Landowners have attempted to moderate these boom‐and‐bust fluctuations via management; however, presently it is unknown whether management can increase or stabilize quail populations in semiarid environments or whether rainfall remains as influential at small spatial extents. Our objectives were to evaluate the efficacy of management at mitigating the effects of rainfall on northern bobwhite (Colinus virginianus) populations on semiarid rangelands and to quantify the influence of rainfall on bobwhite density at smaller spatial extents. We conducted a study to evaluate these objectives during 2014–2020 in the Rio Grande Plains (n = 11 sites; 1,100‒6,500 ha) and Rolling Plains (n = 4 sites; 1,900‒4,000 ha) of Texas, USA. We estimated bobwhite density during late autumn (Dec‒Jan) on all sites using helicopter surveys within a distance‐sampling framework. We also obtained site‐level seasonal rainfall (Apr‒Aug) and quantified management intensity via landowner surveys and a scoring rubric to categorize sites into 3 classes (low, medium, and high management intensity). Bobwhite populations during this study experienced a boom‐bust cycle in both the Rio Grande Plains and Rolling Plains, with mean bobwhite density fluctuating considerably (0.57‒2.96 bobwhites/ha and 0.02‒2.88 bobwhites/ha, respectively). In the Rio Grande Plains, mean bobwhite density significantly increased from low to high management intensity in 2015 (1.12 ± 0.17 bobwhites/ha vs. 2.87 ± 0.39 bobwhites/ha, respectively), 2016 (1.06 ± 0.20 bobwhites/ha vs. 2.96 ± 0.36 bobwhites/ha, respectively), 2017 (0.73 ± 0.16 bobwhites/ha vs. 1.91 ± 0.32 bobwhites/ha, respectively), and 2019 (0.42 ± 0.14 bobwhites/ha vs. 1.01 ± 0.26 bobwhites/ha, respectively; P &lt; 0.05). In addition, rainfall at the site level accounted for a low amount of the variation in bobwhite density (r2 = 0.09; P &lt; 0.01). Similarly, in the Rolling Plains, mean bobwhite density significantly increased from low to high management intensity in 2015 (1.30 ± 0.27 bobwhites/ha vs. 2.20 ± 0.29 bobwhites/ha, respectively) and 2016 (1.26 ± 0.26 bobwhites/ha vs. 2.88 ± 0.34 bobwhites/ha, respectively; P &lt; 0.05). Rainfall at the site level also accounted for a low amount of the variation in bobwhite density (r2 &lt; 0.02; P = 0.82). Our findings suggest that management can increase bobwhite density beyond that of less‐managed properties but does not completely eliminate inter‐annual fluctuations in semiarid environments. In addition, rainfall appears to exert less of an influence on bobwhite density at a site level (e.g., 2,000 ha) than has been documented at a regional level (e.g., ≥8 million ha).

Biological nitrogen fixation of cool‐season legumes in agronomic systems of the Southern Great Plains

AbstractBiological nitrogen fixation (BNF) is a key ecosystem service rendered by legumes, but quantitative information is lacking regarding BNF in the Texas Rolling Plains (TRP), an easterly portion of U.S. Southern Great Plains where cool‐season legumes can typically be grown as cash or cover crops in dryland conditions. Using three diverse cropping systems studies (Site 1, long‐term cotton [Gossypium hirsutum L.]‐cover crop systems; Site 2, short‐term cotton‐cover crop systems; and Site 3, transitional organic wheat [Triticum aestivum L.] system), our research objective was to quantify and compare BNF and associated parameters among four cool‐season legumes (Austrian winter pea [Pisum sativum subsp. Arvense], hairy vetch [Vicia villosa], crimson clover [Trifolium incarnatum], and lentil [Lens culinaris]) in different settings. At Sites 1 and 2, winter pea had growth of 2.73 to 3.44 Mg ha−1, the greatest percent N derived from the atmosphere (%Ndfa; 57.2–72.6%) and, depending on site, the greatest level of BNF (67–74 kg N ha−1). Results from the organic system (Site 3) demonstrated winter pea was also productive in growth and BNF when intercropped with wheat in N‐poor soil, with exceptionally high %Ndfa (92.7%). Hairy vetch and lentil differed in growth and %Ndfa, but had comparable BNF (46–51 kg N ha−1) at Sites 1 and 2. Growth of crimson clover was poor. This data provides insights on how cool‐season legumes differ in BNF in the TRP in a year when legume growth was average for the region. The TRP has a volatile climate, however, indicating further study is needed to fully understand the BNF benefit cool‐season legumes can provide in the region.

Examination of an Anecdotal “October Disappearance” of Northern Bobwhite in the Rolling Plains of Texas Through Demographic Data

Landowners and wildlife managers in the Rolling Plains ecological region of Texas, USA often report encountering northern bobwhite (Colinus virginianus; hereafter, bobwhite) in summer but observe what they perceive as a decrease in quail by early to mid-fall. As most bobwhite research in the Rolling Plains is focused on either breeding season or overwinter survival and movement, researchers rarely record demographic data during this late summer and early fall period. We examined weekly survival probabilities of bobwhite (n = 244) across 7 sites in the western Rolling Plains Ecoregion from August to late November in 2016, 2017, 2019, and 2020. Bobwhites were captured and equipped with very high frequency (VHF) transmitters and tracked 1–5 times/week. We used Akaike’s Information Criterion adjusted for small sample sizes (AICc) to evaluate a suite of candidate models comparing survival among and between years and survival between individual weeks to determine whether an unreported population decrease occurred during the study years. Our comparison of weekly survival probabilities considered survival to be different if 95% confidence intervals did not overlap. Our best supported model held survival constant among years and allowed survival to vary week by week. All other models received little support (ΔAICc > 14.0). Examination of weekly survival probabilities failed to support a demographically driven hypothesis for decreased bobwhite observations from August to November. Though there was an observed decrease of weekly survival in the fourth week of September, it was not different than 16 of the 17 other weeks. We conclude that, for the years we measured, there was no support for a mass die-off hypothesis. Factors outside survival (e.g., a change in bobwhite behavior) may be driving the difference in detectability between late summer and late fall in the Rolling Plains of Texas.

Assessing the Effects of a Winter Wheat Cover Crop on Soil Water Use, Cotton Yield, and Soil Organic Carbon in No-Till Cotton Production Systems

HighlightsSoil water depleted by the cover crop was quickly replenished by spring precipitation.Higher soil water was maintained during the cotton growing season under the cover crop treatment.Cover crops improved soil organic carbon under both irrigated and dryland conditions.Cover crops enhanced crop water productivity under both irrigated and dryland conditions.Abstract. Cover crops provide many soil health benefits to agricultural systems. An interest in growing cover crops in cotton (Gossypium hirsutum L.) production systems has been increasing in the Texas Rolling Plains (TRP) region. Due to limited rainfall and groundwater availability, producers in this semi-arid region are concerned that winter cover crops can reduce soil water availability for a subsequent cotton crop. In addition, the long-term effects of cover crops on soil organic carbon (SOC) are not well studied in this region. The overall goal of this study was to assess the long-term effects of growing a winter wheat (Triticum aestivum) cover crop on soil water, SOC, seed cotton yield, and crop water productivity (CWP) under irrigated and dryland cotton production systems using the Decision Support System for Agrotechnology Transfer (DSSAT) model. Measured data from cover crop experiments conducted at the Texas A&amp;amp;M AgriLife Research Station at Chillicothe from 2011 to 2020 were used to evaluate the CROPGRO-Cotton and CERES-Wheat modules in the DSSAT Cropping System Model. The average percent error (PE) between the simulated and measured seed cotton yield was 0.3% and -0.9%, and that between the simulated and measured aboveground wheat biomass was 1.4% and -3.4% during the calibration and evaluation periods, respectively. For the simulation of SOC, the PE was 8.5% and 7.6% during the calibration and evaluation periods, respectively. Long-term (2001 to 2020) simulations showed that soil water was reduced substantially by the winter wheat cover crop before its termination. However, depleted soil water was quickly replenished by spring precipitation and maintained at a higher level during the cotton growing season. Winter wheat cover crops can potentially improve SOC in irrigated and dryland cotton production systems. The CWP of cotton also improved with a winter wheat cover crop under both irrigated and dryland conditions. We concluded that cover crops could potentially improve soil health and provide a sustainable environment for TRP cotton production. Keywords: CERES-Wheat, CROPGRO-Cotton, DSSAT, Soil health, Texas Rolling Plains (TRP).

Assessing the Effects of a Winter Wheat Cover Crop on Soil Water Use, Cotton Yield, and Soil Organic Carbon in No-Till Cotton Production Systems

HighlightsSoil water depleted by the cover crop was quickly replenished by spring precipitation.Higher soil water was maintained during the cotton growing season under the cover crop treatment.Cover crops improved soil organic carbon under both irrigated and dryland conditions.Cover crops enhanced crop water productivity under both irrigated and dryland conditions.Abstract. Cover crops provide many soil health benefits to agricultural systems. An interest in growing cover crops in cotton (Gossypium hirsutum L.) production systems has been increasing in the Texas Rolling Plains (TRP) region. Due to limited rainfall and groundwater availability, producers in this semi-arid region are concerned that winter cover crops can reduce soil water availability for a subsequent cotton crop. In addition, the long-term effects of cover crops on soil organic carbon (SOC) are not well studied in this region. The overall goal of this study was to assess the long-term effects of growing a winter wheat (Triticum aestivum) cover crop on soil water, SOC, seed cotton yield, and crop water productivity (CWP) under irrigated and dryland cotton production systems using the Decision Support System for Agrotechnology Transfer (DSSAT) model. Measured data from cover crop experiments conducted at the Texas A&amp;amp;M AgriLife Research Station at Chillicothe from 2011 to 2020 were used to evaluate the CROPGRO-Cotton and CERES-Wheat modules in the DSSAT Cropping System Model. The average percent error (PE) between the simulated and measured seed cotton yield was 0.3% and -0.9%, and that between the simulated and measured aboveground wheat biomass was 1.4% and -3.4% during the calibration and evaluation periods, respectively. For the simulation of SOC, the PE was 8.5% and 7.6% during the calibration and evaluation periods, respectively. Long-term (2001 to 2020) simulations showed that soil water was reduced substantially by the winter wheat cover crop before its termination. However, depleted soil water was quickly replenished by spring precipitation and maintained at a higher level during the cotton growing season. Winter wheat cover crops can potentially improve SOC in irrigated and dryland cotton production systems. The CWP of cotton also improved with a winter wheat cover crop under both irrigated and dryland conditions. We concluded that cover crops could potentially improve soil health and provide a sustainable environment for TRP cotton production. Keywords: CERES-Wheat, CROPGRO-Cotton, DSSAT, Soil health, Texas Rolling Plains (TRP).

Evaluation of a Solar-Recharged Micro-GPS Datalogger for Northern Bobwhite in the Rolling Plains of Texas

The use of Global Positioning Systems (GPS) transmitters on northern bobwhite (Colinus virginianus; hereafter, bobwhite) could increase our understanding of fine-scale movements and habitat use for a declining game bird species. We evaluated solar-recharged micro-GPS dataloggers to determine the effectiveness of the units on free-ranging bobwhite and we conducted a controlled experiment to determine the accuracy of the dataloggers under a variety of canopy cover. We deployed the micro-GPS dataloggers on 25 bobwhites between August 2016 and April 2017 across 4 different ranches in the Rolling Plains of West Texas, USA. Accuracy (± standard error) for the 8 dataloggers across 3 trials for the stationary tests was 25.4 ± 3.8 m. Daily movement of bobwhite averaged 0.96 ± 0.09 km and morning movements averaged 0.49 ± 0.07 km. Average 95% and 50% minimum convex polygons for bobwhite area utilization were 15.2 ha and 3.6 ha, respectively. Our data indicate that solar-recharged micro-GPS dataloggers can be used to monitor bobwhites’ short-term fine-scale movements in West Texas.

Winter Cover Crop Impact on Soil Health and Nutrients in Texas Rolling Plains Dryland Cotton

Winter Cover Crop Impact on Soil Health and Nutrients in Texas Rolling Plains Dryland Cotton

Evaluation of the DSSAT‐CANEGRO model for simulating the growth of energy cane (Saccharumspp.), a biofuel feedstock crop

AbstractThe Decision Support System for Agrotechnology Transfer for sugarcane (DSSAT‐CANEGRO) was evaluated for simulating the growth of energy cane (Saccharumspp. hybrid), a perennial biofuel feedstock crop. Plant growth data collected from a field experiment conducted in the semi‐arid Texas Rolling Plains was used for model calibration and validation. All model performance indicators showed good agreement between simulated and measured biomass accumulation. After calibration, model was used for simulating plant cane and ratoon biomass yield using long‐term (i.e., 33‐year) historic weather data under rainfed and two irrigation levels. The irrigated treatments were a) 300 mm seasonal supplementary irrigation and b) auto‐irrigation to replenish soil water in the profile to field capacity. The long‐term average biomass yield of plant cane (6.4 ± 0.47 Mg ha–1) and ratoon (14.4 ± 0.92 Mg ha–1) were the lowest when simulated under rainfed conditions. Supplemental irrigation with 300 mm irrigation water significantly increased yield of both crops (14.6 ± 0.53 Mg ha–1for plant cane and 29.5 ± 1.33 Mg ha–1for ratoon). The auto‐irrigation option substantially increased the amount of water applied and resulted in an average biomass of 16.7 ± 0.24 Mg ha–1for plant cane and 44.4 ± 0.36 Mg ha–1for ratoon. Biomass water use efficiency was the highest for ratoon due to its longer growing season. This modeling study showed reasonable performance of DSSAT‐CANEGRO for simulating energy cane growth. Irrigation experiments using historical data showed energy cane as a competitive biomass crop in the Texas Rolling Plains region.

A Helminth Survey of Northern Bobwhite Quail (Colinus virginianus) and Passerines in the Rolling Plains Ecoregion of Texas.

The Northern bobwhite quail (Colinus virginianus) is a popular game bird that has been experiencing a well-documented decline throughout Texas since the 1960s. While much of this decline has been attributed to habitat loss and fragmentation, recent studies have identified other factors that may also contribute to decreasing quail populations. Parasites, in particular, have become increasingly recognized as possible stressors of quail, and some species, particularly the eyeworm (Oxyspirura petrowi) and cecal worm (Aulonocephalus pennula) are highly prevalent in Texas quails. Eyeworm infection has also been documented in some passerines, suggesting helminth infection may be shared between bird species. However, the lack of comprehensive helminth surveys has rendered the extent of shared infection between quail and passerines in the ecoregion unclear. Thus, helminth surveys were conducted on bobwhite, scaled quail (Callipepla squamata), Northern mockingbirds (Mimus polyglottos), curve-billed thrashers (Toxistoma curvirostre), and Northern cardinals (Cardinalis cardinalis) to contribute data to existing parasitological gaps for birds in the Rolling Plains ecoregion of Texas. Birds were trapped across 3 counties in the Texas Rolling Plains from March to October 2019. Necropsies were conducted on 54 individuals (36 quail and 18 passerines), and extracted helminths were microscopically identified. Nematode, cestode, and acanthocephalan helminths representing at least 10 helminth species were found. Specifically, A. pennula and O. petrowi had the highest prevalence, and O. petrowi was documented in all of the study species. This research adds to the body of knowledge regarding parasitic infections in quail and passerines of the Rolling Plains ecoregion and highlights the potential consequences of shared infection of eyeworms among these bird species.

Evaluating a herpetofaunal monitoring program in the Rolling Plains of Texas.

We evaluated the herpetofaunal monitoring program on a state-owned property in the Rolling Plains ecoregion of Texas to determine whether the current study design and survey effort are meeting the following monitoring objectives: (1) inventory herpetofaunal diversity on the property, (2) improve understanding of herpetofaunal habitat preferences, and (3) track herpetofaunal response to land management activities. We used the iChao1 species richness estimator to evaluate the sample completeness of the current dataset, which was collected intermittently from 2004 to 2016. Species richness was evaluated by site and year as well as pooled across sites and years. Observed species richness across all sites and years was 23 species, and estimated richness was 23.999 (23.090-34.052, 95% CI). Observed species richness for each year was less than the cumulative total, with 20 species observed in 2004, 6 species observed in 2013, 11 species observed in 2014, and 19 species observed in 2016. The estimated species richness for individual years of sampling ranged from 6.250 to 39.320 species. Our analysis suggests that inadequate sampling design and effort prevents all three objectives from being addressed using the existing dataset. Necessary improvements to the monitoring program to meet all objectives include increasing the spatial and temporal scale of the monitoring effort and utilizing a random sampling protocol. Monitoring methods that address variation in detection probability, such as occupancy and mark-recapture, will also need to play a role. Our findings show that monitoring programs require substantial investment in materials and personnel to obtain datasets sufficient for rigorous biodiversity monitoring.

Effective Management Practices for Increasing Native Plant Diversity on Mesquite Savanna-Texas Wintergrass-Dominated Rangelands

Throughout the Rolling Plains and Cross Timbers ecoregions of Texas, native grassland plant communities have been converted into low-diversity plant communities by long-term, intensive overgrazing by cattle and fire suppression. Much of the historical plant community has become dominated by annuals, Texas wintergrass (Nassella leucotricha), and honey mesquite (Prosopis glandulosa). This degradation has been so severe that many native bird species, including Northern bobwhite (Colinus virginianus), have experienced drastic population declines. We conducted a small-plot study to determine effective management actions for transforming mesquite savanna−Texas wintergrass communities to diverse native plant communities supportive of native wildlife species. We tested multiple management practices following mechanical mesquite brush removal, including seeding, timed treatments of herbicide, prescribed burns, and high-intensity, short-duration cattle grazing. Results indicated that plots receiving early spring treatments of herbicide followed by burning and grazing over 2 consecutive yr best reduced cool-season grasses and promoted overall restoration goals by increasing native warm-season grass and forb establishment.

Assessment of the helminth fauna in northern bobwhites (Colinus virginianus) occurring within South Texas.

Populations of northern bobwhites (Colinus virginianus; hereafter bobwhite) have been declining across their geographic range in North America, prompting consideration of the role parasites may play. We conducted this study to learn about the helminth fauna in South Texas, a region that supports a sustainable bobwhite population. Helminths were examined from 356 bobwhites collected during the 2014-2015 (n = 124) and 2015-2016 (n = 232) hunting seasons, when increasing trends in precipitation were observed in comparison with the previous two years. Ten helminth species were found, consisting of 14,127 individuals. Of these, all are heteroxenous parasites and three are pathogenic (Dispharynx nasuta, Tetrameres pattersoni and Oxyspirura petrowi). Aulonocephalus pennula numerically dominated the component community (81% prevalence, 99% of the total helminths found), whereas each of the remaining species occurred rarely (≤9% prevalence) and contributed few individuals (≤0.4%) to the helminth community. Prevalence and abundance of A. pennula were not influenced by host age, sex or body mass, but abundance was higher during the 2014-2015 than the 2015-2016 hunting season. Our findings indicate that the helminth community in bobwhites from South Texas can vary during long-term, highly variable precipitation conditions and these communities are more similar to those found in the Rolling Plains of Texas than those found in the eastern part of the bobwhite's geographic range in the US.