PSXI-18 Nitrogen fertilization management of winter pastures for stocker cattle production

Bermudagrass is often over-seeded with a cool-season annual grass for grazing purposes. In the Gulf Coast region, summer perennials will not become dormant until there are low soil and ambient temperatures. Nitrogen fertilizer is an expensive input and its split application for winter pastures is recommended. The objective of this experiment was to evaluate the time of application of N fertilizer or its substitution with red clover as a source of N. Three treatments were evaluated in 3 consecutive years (2 replicates per year) on annual ryegrass (cv. Marshall) no-tilled planted (45 kg/ha) on Tifton-85 bermudagrass: 1) Urea in late November and mid-late January; 2) Red clover planted with annual ryegrass; 3) Urea in January only. Thirty crossbred steers (203±24 kg) were blocked by BW and randomly assigned to 1 of 6 groups. Each group were continuously stocked on 1.34 ha pastures for 90 d. Forage mass, botanical composition, and nutritive value of the pastures were determined from the time of the first N application and every 15 d thereafter. There was treatment x year interaction (P = 0.03) in botanical composition. Greater proportions (P = 0.03) of bermudagrass were present on the 2-application treatment on every sampling date until d 15 of the grazing period in Year 1 and 3. This was a result of N absorbed by bermudagrass which impacted its nutritive value (P = 0.01) although not forage production (P = 0.07). In Year 2, annual ryegrass dominated the swards due to a cold artic front in early November. Steers grazing fertilized treatments had greater gains (P = 0.04), while production per ha was greater (P = 0.03) when N was applied in January than when no N was applied. Hay production (kg DM/ha) was similar (P = 0.06) among treatments. Opportunities for improved economics of production and enhanced sustainability appear to be realistic objectives with changes in fertilization strategy.

A Texas-specific VS30 map incorporating geology and VS30 observations

A Texas-specific [Formula: see text] map that uses geostatistical kriging integrated with a region-specific geologic proxy, field measurements of [Formula: see text], and P-wave seismogram estimates of [Formula: see text] is developed. The region-specific geologic proxy is used first to predict [Formula: see text] from the surface geologic conditions across the state, and then geostatistical kriging with an external drift is used to incorporate the local [Formula: see text] measurements/estimates into the map. Compared with the [Formula: see text] map of Texas developed from a topographic slope proxy, the Texas-specific [Formula: see text] map predicts larger [Formula: see text] values across much of Texas, except for the Gulf Coast region where the values are similar. The utilization of kriging brings the Texas-specific [Formula: see text] map into better agreement with the in situ measurements and estimates of [Formula: see text]. The sensitivity of predicted ground motions by ShakeMap to changes in [Formula: see text] values is evaluated with a scenario earthquake in the Dallas–Fort Worth area. The results suggest smaller predicted ground motions due to the generally larger values of [Formula: see text] in the Texas-specific [Formula: see text] map as compared to the [Formula: see text] from the topographic proxy.

First report of cucurbit yellow stunting disorder virus and cucurbit chlorotic yellows virus in cucurbit crops in Alabama

During the summer and fall of 2020, foliar yellowing symptoms, including leaf mottle and interveinal yellowing with green veins were observed on several melon, squash, and cucumber plants in commercial fields in Alabama, USA. These foliar symptoms were similar to those caused by the whitefly-transmitted yellowing viruses, cucurbit chlorotic yellows virus (CCYV) and cucurbit yellow stunting disorder virus (CYSDV) (both genus Crinivirus, Closteroviridae). A total of 231 leaf samples showing yellowing, interveinal chlorosis, and mottling (e-Xtra 1, 2) were collected from individual plants from 25 commercial fields in Alabama (70 watermelon, 52 melon, 34 pumpkin, 50 squash, and 25 cucumber) during two sampling periods, June (spring/summer season) and October (fall season) 2020. Total RNA, extracted as described in Tamang et al. (2021), was used in reverse transcription polymerase chain reaction (RT-PCR) with primer sets designed to amplify portions of the CCYV and CYSDV RNA-dependent RNA polymerase (RdRp) genes encoded on RNA1 of these viruses (Mondal et al. 2021, submitted; Kavalappara et al., 2021). Single infections of either CYSDV or CCYV were found in 53 of 57 infected cucurbit samples (of 231 total plants), whereas both viruses were detected in four samples, all squash. In June 2020 near the end of the spring season, CYSDV was identified from 20 of 114 total cucurbit plants tested (17.5%), but CCYV was not identified from any plants. During the fall season, 37 of 117 plants (32%) tested positive for the presence of one or both criniviruses. Of the 37 virus-positive samples from the fall season, 26 were singly infected with CCYV (70%), seven were singly infected with CYSDV (19%), and four were infected with both CYSDV and CCYV (11%). The RdRp amplicon was sequenced from three CCYV-infected plants (2 squash; GenBank Accession No. MZ073347, MZ073348; 1 cucumber, MZ073349) and one CYSDV-infected plant (melon, MZ073350); the 857 nt sequenced portion of the CCYV RdRp gene was found to share 99% identity with the same sequence of CCYV RNA1 isolates from Israel (MH477611.1) and California (MW680157), whereas the 494 nt CYSDV amplicon shared 100% sequence identity with the comparable sequence from RNA1 of a CYSDV isolate from Arizona (EF547827.1). In addition, all of the CYSDV and CCYV infections were confirmed using a second set of primers that amplified 394 and 372 nt sections of the coat protein gene of each virus, respectively (Wintermantel et al., 2009; 2019), encoded on RNA2 of each viral genome. Furthermore, a recently developed multiplex RT-qPCR method (Mondal et al. 2021, submitted) was used to confirm four representative CYSDV and CCYV infections each. This is the first report of CYSDV and CCYV in cucurbit crops from Alabama. Surprisingly, CYSDV was only found in melon plants (20 of 52, 38%), whereas CCYV was only found in squash, pumpkin, and cucumber (26 of 109, 24%); no watermelon plants were infected with either virus, even though watermelon is a known host of both viruses. The identification of CCYV and CYSDV in Alabama, along with a recent report of both criniviruses from nearby Georgia (Kavalappara et al., 2021) illustrates the need for a more thorough sampling of cucurbit crops, further monitoring of the whitefly vector, Bemisia tabaci, and the identification of alternate hosts of these viruses to better understand the epidemiology of these viruses in Alabama and throughout the Gulf Coast region.

Historic and Contemporary Environmental Justice Issues among Native Americans in the Gulf Coast Region of the United States

Settler-colonialism is founded in environmental racism, and environmental justice is foundational to all forms of decolonialization. Native American groups located in the Gulf Coast Region of the United States are particularly vulnerable to environmental justice issues such as climate change and oil spills due to their geographic location and reliance on the coastal region for economic and social resources. This study used the framework of historical oppression, resilience, and transcendence (FHORT) to explore the historic and contemporary forms of environmental injustice experienced by a Native American tribe in the Gulf Coast region of the United States. This critical ethnography analyzeda series of individual, family, and focus group semi-structured qualitative interviews with a total of 208 participants. Following the critical ethnographic method, data were interpreted through reconstructive analysis using NVivo. Findings of this study reveal the continuing impact of the BP oil spill and difficulty accessing resources following the spill, complicated by the tribe’s lack of federal recognition. Additional themes include the continuing impact of coastal erosion, historical and contemporary land loss, geographic marginalization, and concerns about a loss of tribal identity when tribal members are forced to relocate. Lack of federal tribal recognition has exacerbated all of these issues for this tribe. This study supports national findings that Native American groups experience extensive historic and contemporary environmental injustices and contextualizes these findings for a Native American tribe in the Gulf Coast region of the United States. Recognizing Native American sovereignty is key to addressing the environmental justice issues described.

Turbidite lobe deposits in a canyon-fill system

The lower Wilcox turbidite lobe deposits located above the Cretaceous carbonate shelf edges in the Central Gulf Coast region of Texas are considered as prominent targets for petroleum production. Reliably interpreting lobe deposits is challenging due to their complex seismic geometries and isolated occurrences. The Paleogene Wilcox Group hosting the lobe deposits is a thick sequence, consisting of terrigenous clastic sediment deposits formed in marine and terrestrial environments. Multi-phase regression and transgression during the late Paleocene to the early Eocene complicated the local depositional structures and developed the incised canyon features. The turbidity-flow deposits, originated from canyon-margin deltas, formed lobes in the lower onlap fill of the canyon. We analyze both seismic data and well logs to determine the morphology and rock properties of the depositional facies along the canyon system. We also utilize seismic attributes to identify the shape and lateral variations of the sandy turbidite lobe deposits inside the canyon-fill sequence. Analyses of the selected attributes, including instantaneous phase, RMS amplitude, and spectral decomposition, indicate that the prograding deltaic sediments crawled over the steep canyon walls, followed by retrograding and consequential excavation of the canyon walls, resulting in an elongated funnel shaped canyon. During the process, the sand bodies were transported into the underwater distributary channels across the basin floor, and generated the turbidite lobe deposits within the lower onlapping canyon fill.

Tolerance of rhizoma perennial peanut to glyphosate and triclopyr

Rhizoma perennial peanut (RPP) is well adapted to the Gulf Coast region of the United States, but its varietal tolerance to glyphosate and triclopyr is not well defined. The research was conducted to determine the effect of various rates of glyphosate and triclopyr on established RPP, and the response of common RPP varieties to these herbicides. The RPP sward was approximately 7 yr younger at Zolfo Springs than at the Ona location. RPP showed moderate tolerance to glyphosate and triclopyr application, and injury level did not differ with the age of RPP sward. However, biomass production was negatively influenced by the age of the RPP sward. Overall, injury from glyphosate applications did not exceed 40% at either site. The glyphosate rate for 20% biomass reduction was predicted to be 0.53 and 2.17 kg ae ha−1 at Zolfo Springs and Ona, respectively. RPP injury from triclopyr was greater at the Zolfo Springs location than at Ona, and the triclopyr rate predicted to result in a 20% biomass reduction was 0.45 and 0.99 kg ae ha−1 at the Zolfo Springs and Ona locations, respectively. There was a difference on RPP varieties response to glyphosate and triclopyr application. ‘Florigraze’ and ‘Ona 33’ were less tolerant to glyphosate compared to ‘UF-Tito’ and ‘Ecoturf’ at 30 d after treatment. Likewise, UF-Tito and Florigraze were less tolerant to triclopyr compared to Ona 33 and Ecoturf. Overall, Florigraze showed highest injury and at least 2-fold reduction on biomass compared to the other three varieties from glyphosate or triclopyr application. Results from this research indicate that glyphosate and triclopyr appear to be safe to apply to long-established RPP stands, but herbicide rate and RPP varieties should be considered if stands are <5 yr old.

PSVIII-26 Extending the grazing season for grass-fed beef production into the spring transition period

In the Gulf Coast region, the spring transition period is a 45–60 d period between late April and mid-June. Red and white clovers’ growth pattern is delayed compared to winter grasses making them suitable for this transition period; however, an appropriate rest period allowing stockpiling is needed. Three treatments were evaluated on pastures planted in September of three consecutive years: 1) grazed until mid-February (MF); 2) grazed until first week of March (EM); and 3) grazed until last week of March (LM). Grazing re-started on May 1. Pasture was a mixed of annual ryegrass, red, white and berseem clover. Each year, 24 crossbred steers (330 ± 11 kg) were blocked by BW, allotted to 1 of 6 groups (2 replicates/treatment), and continuously stocked at 995 kg BW/ha. Forage mass at the beginning of the grazing period was greater (P &lt; 0.05) in MF, followed by EM and LM. This represented a forage allowance of 2.0, 1.6, and 1.1 kg DM/kg BW. On d0, the proportion of annual ryegrass was greater (P &lt; 0.05) in MF than in EM and the smallest in LM. Proportion of clovers was greater (P = 0.04) in EM in Year 2 while MF and LM were similar but greater for MF in Year 1. Berseem clover represented 59% of the clover biomass in MF while red clover was 72% of the clover biomass in LM. Proportion of clovers decreased with time while annual ryegrass became mature affecting its palatability. Steers that grazed on MF and EM had greater ADG (1.83 and 1.71 kg) than those on LM (1.41 kg). Grazing season was longer (P = 0.03) for MF (66 days) than for LM (39 days) while EM was intermediate (50 days). A rest period from early March to late April would allow grazing of high-quality pastures during the spring transition period.