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Traffic simulators are often utilized when researching turfgrass wear tolerance and recovery. However, the availability of a durable traffic simulator capable of producing dynamic force is limited. Therefore, the objectives of this research were to: (i) evaluate a novel traffic simulator with improved durability and capable of producing dynamic force and (ii) evaluate the biophysical effects of the traffic simulator on a native soil turfgrass system. The Baldree traffic simulator is a modified Ryan GA 30 (Jacobsen, A Textron Company, Charlotte, NC) riding aerification unit, equipped with fabricated, spring loaded steel plate feet studded with screw in cleats. The effects of this unit on a 'Tifway' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] system established on a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) were evaluated at the Coastal Plains Experiment Station, Tifton, GA. Factors included location (1 and 2) and traffic rate (0, 12, and 24 passes applied over a 6 wk period). Field data included soil bulk density, turf density, and percent green turf cover. An in-ground force plate at the McPhail Equine Performance Center, East Lansing, MI was used to quantify vertical and net shear ground reaction force produced by the Baldree traffic simulator when operated in the forward and backward direction. The Baldree traffic simulator produced more cleat marks per pass than the Brinkman and Cady traffic simulators. At the low traffic rate the Baldree traffic simulator increased soil bulk density, while turf density and percent green turf cover decreased; therefore, the tool can be used to simulate heavy traffic conditions with a minimum number of passes. [ABSTRACT FROM AUTHOR]

Management zones (MZs) for southern root-knot nematode (RKN) from the integration of terrain (TR) and edaphic (ED) field features might facilitate variable rate nematicide applications. This study was conducted on 11 coastal plain fields in the USA. The relationships between RKN populations and five soil ED and TR attributes (apparent soil electrical conductivity [shallow (ECa-s) and deep (ECa-d)], elevation (EL), slope (SL), and changes in bare soil reflectance) were analyzed using canonical correlation. Using two ED and TR data sets, canonical predictors were used for zone delineation. Although the results showed that the zones with RKN population above the RKN field average were associated with the lowest values of ECa-s, ECa-d, normalized difference vegetation index (NDVI), and SL with respect to field average values, zone segregation was enough using ECa-s and ECa-d data. The results suggest the potential for using soil properties to identify RKN risk zones. [ABSTRACT FROM AUTHOR]

Abstract: Conservation tillage is a commonly adopted best management practice for improving soil quality and reducing erosion. However, there are currently no methods in place to monitor conservation tillage adoption at the watershed scale. The primary objective of this study was to evaluate the usefulness of Landsat TM data as a tool to depict conservation tillage in a small Coastal Plain watershed. Satellite imagery was used to calculate four commonly used indices: Normalized Difference Vegetation Index, Crop Residue Cover Index, Normalized Difference Tillage Index, and the Simple Tillage Index. Ground truth data consisted of a windshield survey, assigning each site a tillage regime (conventional or conservation tillage) at 138 locations throughout the watershed and surrounding areas. A logistical regression approach was used on two subsets of the data set (n = 20 or n = 44) to determine the influence of the number of ground control points on the success of modeling the occurrence of Conservation tillage. The most accurate model was re-applied to the satellite image and evaluated using an independent sample of 94 survey sites. Results indicate that the normalized difference tillage and simple tillage indices performed best, with an overall accuracy of 71% and 78% for models developed using n = 20 and n= 44 sample locations, respectively. Errors were typically in the form of commission. Results are encouraging and suggest that currently available satellite imagery can be used for rapid assessment of conservation tillage adoption using minimal a priori information. [ABSTRACT FROM AUTHOR]

Conservation tillage is a well known best management practice that improves soil quality, reduces runoff and erosion, and increases infiltration. However, a rapid assessment strategy for quantifying the rate and spatial distribution of conservation tillage practices is lacking. This study was designed to evaluate the sensitivity of a remotely derived crop residue cover index for depicting conventional tillage (CT), strip tillage (ST), and no-tillage (NT). systems in a cotton-corn-peanut rotation in tile southeastern Coastal Plain. Treatments consisted of CT (rip and bed operation), NT, NT with subsoiling, and STE. Remotely sensed data were acquired three times prior to canopy closure, using a handheld multispectral radiometer (485 to 1,650 nm) and thermal imager (7,000 to 14,000 nm). Using a combination of visible and near-infrared spectra, a crop residue cover index was calculated and evaluated. Results showed that crop residue cover is greatest in years, planted with peanut or cotton--likely due to the later winter cover crop termination date compared to years when corn is planted. The. crop residue cover index outperformed the thermal infrared, accurately separating conventional from conservation tillage treatments in four out of six data acquisitions in 2004 and 2006. Differentiation among conservation tillage treatments was inconsistent. Regression analyses showed that a strong linear relationship existed between tile crop residue cover index and measured crop residue cover (r² = 0.51 to 0.86, alpha = 0.10).These data suggest that remotely sensed data may be used as a rapid, field-scale indicator of conservation tillage adoption. Rapid assessment methodologies are necessary to quantify the impact of conservation practice adoption on Water quality/quantity, assess adoption rates, and improve the placement of conservation tillage practices at local, watershed and regional scales. [ABSTRACT FROM AUTHOR]

Airborne thermal infrared (TIR) imagery is a promising and innovative tool for assessing canopy response to a range of stressors. However, the expense associated with acquiring imagery for agricultural management is often cost-prohibitive. The objective of this study was to evaluate a less expensive system, an unmanned airvehicle (UAV) equipped with a TIR sensor, for detecting cotton (Gossypium hirsutum L.)response to irrigation and crop residue management. The experimental site was located on a 6.1 ha field in the Tennessee Valley Research and Extension Center located in Belle Mina, Alabama, where landscapes are gently rolling and soils are highly weathered Rhodic Paleudults. Treatments consisted of irrigation (dryland or subsurface drip irrigation) and crop residue cover (no cover or winter wheat (Triticum aestivum L.)). TIR (7 to 14 µm) imagery was acquired on 18 July 2006 at an altitude of 90 m and spatial resolution of O.5 m. Coincident with image acquisition, ground truth data consisting of soil water content (0-25 cm), stomatal conductance, and canopy cover were measured within a 1 m radius of each sample location. All sample locations were georeferenced using a real-time kinematic (RTK) GPS survey unit. Analysis of sample locations acquired in multiple flight lines was used to assess the stability and repeatability of the UAV system during an acquisition. Compared to field measurements of stomatal conductance with CVs ranging from 2% to 75%, variability in TIR emittance (CV < 40%) was within the observed tolerance of ground truth measurements of stomatal conductance. Significant differences in canopy cover and stomatal conductance across irrigation treatments allowed testing of the sensitivity of the UAV system. A negative correlation was observed between TIR emittance and stomatal conductance (r = -0.48) and canopy closure (r = -0.44), indicating increasing canopy stress as stomatal conductance and canopy closure decreased. TIR emittance exhibited greater sensitivity to canopy response compared to ground truth measurements, differentiating between irrigation and crop residue cover treatments. TIR imagery acquired with a low-altitude UAV can be used as a tool to manage within-season canopy stress. [ABSTRACT FROM AUTHOR]

Reduced tillage and surface residue increases infiltration, soil water content, and plant available water, while at the same time decreasing runoff and sedimentation. However, there is a general lack of knowledge and appreciation regarding the impact conservation tillage has on sustainable water resources. The objective of this study was to estimate water savings as a result of conservation tillage adoption in Georgia. Total acreages by crop (cotton, corn, and peanut) and tillage (conventional and conservation) were obtained via the Conservation Technology Information Center for the 2004 growing season. Rainfall simulation studies conducted over row-cropped lands in conventional and conservation tillage were obtained for soils in the Coastal Plain and Piedmont physiographies. Data were integrated within a geographical information system. In 2004, cotton, corn, and peanuts represented 85% of row crop production in Georgia, with nearly 90% of the acreage in the Coastal Plain. Conservation tillage systems are currently in place on approximately 30% of those acreages, primarily in the form of strip tillage. Results from rainfall simulation studies indicate that conservation tillage can reduce runoff and increase infiltration in these systems by 29% to 46%. Extrapolating these results to the state, conservation tillage reduced estimated statewide, irrigated water requirements from 4% to 14%. Increasing conservation tillage to 40% in intensively row-cropped counties where conservation tillage adoption rates were less than the national average (40%) increased estimated water savings by an additional 1% to 6%. [ABSTRACT FROM AUTHOR]

Conservation programs developed and implemented by the USDA have led to land-use changes of large areas throughout the U.S. These changes in land-use may lead to changes in evapotranspiration and infiltration and subsequently to dramatic differences in hydrologic response. The impact of recent land-use changes was evaluated using observed precipitation and streamflow data from the Little River watershed in south-central Georgia in the U.S. Land-use patterns within the watershed were, examined through classification of satellite images collected from 1975 to 2003. While some changes in land-use were determined, analysis of the data indicated that the overall changes were less than the typical classification errors obtained. Based on the analysis of the satellite imagery, conservation practices implemented in the Little River watershed have not significantly altered total forest acreage. It addition, 34 years of hydrologic data collected from this watershed do not indicate any significant changes in hydrologic patterns. The long-term average ratio of annual flow to annual precipitation for the Little River watershed has remained stable at approximately 0.27. Year-to-year variation of the ratio varied from a high of 0.41 observed during a year with above-normal winter rainfall to 0.06 observed during a year with very low annual rainfall. When subwatersheds of the Little River were compared, significant differences in their responsiveness to rainfall were found. Linear regression between precipitation and streamflow produced regression coefficients between 0.62 and 0.90. These differences were attributed to differences in physical characteristics and land-use. Long-term data from the watersheds indicate that streamflow response is dominated by annual and seasonal precipitation characteristics. [ABSTRACT FROM AUTHOR]

The watershed-scale effects of agricultural conservation practices are not well understood. A baseline calibration and an input parameter sensitivity analysis were conducted for simulation of watershed-scale hydrology in the Little River Experimental Watershed (LREW) in the Coastal Plain near Tifton, Georgia. The Soil and Water Assessment Tool (SWAT) was manually calibrated to simulate the hydrologic budget components measured for the 16.9 km² subwatershed K of the LREW from 1995 to 2004. A local sensitivity analysis was performed on 16 input variables. The sum of squares of the differences between observed and simulated annual averages for baseflow, stormflow, evapotranspiration, and deep percolation was 19 mm²; average annual precipitation was 1136 mm. The monthly Nash-Sutcliffe model efficiency (NSE) for total water yield (TWYLD) was 0.79 for the ten-year period. Daily NSE for TWYLD was 0.42. The monthly NSE for three years with above-average rainfall was 0.89, while monthly NSE was 0.59 for seven years with below annual average rainfall, indicating that SWAT's predictive capabilities are less well-suited for drier conditions. Monthly average TWYLD for the high-flow winter to early spring season was underpredicted, while the low-flow late summer to autumn TWYLD was overpredicted. Results were negatively influenced when seasonal tropical storms occurred during a dry year The most sensitive parameters for TWYLD were curve number for crop land (CN2(crop)), soil available water content (SOL_AWC), and soil evaporation compensation factor (ESCO). The most sensitive parameters for storm flow were CN2(crop), curve number for forested land (CN2(forest)), soil bulk density (SOL_BD), and SOL_AWC. The most sensitive parameters for baseflow were CN2(crop), CN2(forest), ESCO, and SOL_AWC. Identification of the sensitive SWAT parameters in the LREW provides modelers in the Coastal Plain physiographic region with focus for SWAT calibration. [ABSTRACT FROM AUTHOR]

Dense dendritic stream networks in the Tifton Upland (southeastern U.S. coastal plain) provide an opportunity to determine the effects of land management practices on individual farms on downstream hydrology and water quality. A typical farm will be drained by two or three small streams. The streams may be bordered by riparian forests or impounded into farm ponds. Two adjacent farm-scale basins, both of which were 50 to 60 ha (124 to 148 ac) in size were compared for seven years to determine the effects of upstream agricultural land uses, downstream riparian zones, and small impoundments on stream water quality and hydrology. Stream water quality was sampled at four points on the two basins and at a downstream outlet where the two streams came together in a farm pond. The north basin had more cropland than the south basin and had much more area in plastic-covered beds for vegetable production. The south basin had less land in crop production and much more of the total basin area in farm ponds used to supply irrigation water. The north basin had more surface runoff and higher loads of all nutrients and sediment. The south basin had only 55% of the total runoff of the north basin, probably due to the presence of about 6% of the total watershed area in farm ponds. Up to 26% of the north basin (38% of total cropland) was occupied by wide plastic-covered beds in the last two years of the study. Large quantities of sediment transported in surface runoff from these fields on the north basin led to increases in sediment concentrations and loads of over 100 times compared to both the south basin and to earlier years of the study. Based on reductions in differences in loads and concentrations between upstream and downstream sites, there is less potential to reduce nutrients and sediment once these materials are in stream flow than when water is moving to streams through a riparian buffer. A downstream pond that received inputs from both the north and south basins had significantly lower concentrations of most nutrients and sediments than either of the upstream sampling sites. [ABSTRACT FROM AUTHOR]

Background: Hepatitis C virus infection persists after liver transplantation and causes recurrent liver injury in the majority of patients. Standard dose interferon therapy has been largely unsuccessful for hepatitis C in transplant recipients., Methods: Twelve patients, at least 7 months posttransplant, with detectable hepatitis C virus RNA in serum and features of hepatitis C on liver biopsy were randomized to interferon-alpha2a, 3 mU daily for 12 months (n=8) or no treatment (n=4). The tolerability of daily interferon dosing in liver transplant recipients was evaluated and effects on hepatitis C virus RNA level, quasispecies evolution, and liver histology were studied., Results: Treated patients had an improvement in histological activity index at the end of therapy relative to controls (median reduction of 2 versus median increase of 1.5) (P=0.04). Four treated patients had a virological response (all bDNA negative, one qualitative polymerase chain reaction negative) compared with none of the untreated patients. Only two of six treated patients tested had evidence of quasispecies diversification on therapy. Seven of eight patients in the treatment group required dose reduction for fatigue and/or depression. They tolerated 1.5 mU of interferon-alpha2a daily. Two treated patients developed graft dysfunction, one of who had histological evidence of rejection and subsequent graft loss., Conclusions: Low daily doses of interferon were tolerated by liver transplant recipients and provided histological benefit without associated quasispecies diversification in most cases. These findings provide a rationale to study low dose daily or pegylated interferon maintenance therapy for the management of hepatitis C posttransplant.

Resistance of the hepatitis C virus (HCV) to interferon-alpha (IFN-alpha) therapy in patients with hepatitis C may be genetically controlled by an IFN sensitivity-determining region (ISDR) within the non-structural 5A (NS5A) gene. To assess whether HCV 1b strains carrying a 'resistant' type of ISDR are selected during unsuccessful IFN therapy, we analysed the evolution of the NS5A quasispecies, as detected by the clonal frequency analysis technique, and of the ISDR sequence by nucleotide sequence determination, in 11 patients showing no virological response during two consecutive cycles of IFN-alpha therapy. IFN-resistant patients had a homogeneous ISDR quasispecies with sequences identical to those described as 'resistant-' or 'intermediate-' type ISDR. After retreatment with IFN, further selection towards a homogeneous viral population was observed and 10 out of 11 patients had only one variant of HCV with no or just one single amino acid mutation within the ISDR sequence. Treatment and retreatment with IFN was associated in our non-responder patients with evolution of the ISDR quasispecies towards a rather homogeneous viral population carrying a conserved or minimally mutated ISDR motif, supporting the idea that this motif may be relevant for IFN resistance in HCV 1b-infected individuals.

Alpha interferon (IFN-alpha) treatment is effective on a long-term basis in only 15 to 25% of patients with chronic hepatitis C. The results of recent trials indicate that response rates can be significantly increased when IFN-alpha is given in combination with ribavirin. However, a large number of patients do not respond even to combination therapy. Nonresponsiveness to IFN is characterized by evolution of the hepatitis C virus (HCV) quasispecies. Little is known about the changes occurring within the HCV genomes when nonresponder patients are retreated with IFN or with IFN plus ribavirin. In the present study we have examined the genetic divergence of HCV quasispecies during unsuccessful retreatment with IFN or IFN plus ribavirin. Fifteen nonresponder patients with HCV-1 (4 patients with HCV-1a and 11 patients with HCV-1b) infection were studied while being retreated for 2 months (phase 1) with IFN-alpha (6 MU given three times a week), followed by IFN plus ribavirin or IFN alone for an additional 6 months (phase 2). HCV quasispecies diversification in the E2 hypervariable region-1 (HVR1) and in the putative NS5A IFN sensitivity determining region (ISDR) were analyzed for phase 1 and phase 2 by using the heteroduplex tracking assay and clonal frequency analysis techniques. A major finding of this study was the relatively rapid evolution of the HCV quasispecies observed in both treatment groups during the early phase 1 compared to the late phase 2 of treatment. The rate of quasispecies diversification in HVR1 was significantly higher during phase 1 versus phase 2 both in patients who received IFN plus ribavirin (P = 0.017) and in patients who received IFN alone (P = 0. 05). A trend toward higher rates of quasispecies evolution in the ISDR was also observed during phase 1 in both groups, although the results did not reach statistical significance. However, the NS5A quasispecies appeared to be rather homogeneous and stable in most nonresponder patients, suggesting the presence of a single well-fit major variant, resistant to antiviral treatment, in agreement with published data which have identified an IFN sensitivity determinant region within the NS5A. During the entire 8 months of retreatment, there was no difference in the rate of fixation of mutation between patients who received combination therapy and patients who were treated with IFN alone, suggesting that ribavirin had no major effects on the evolution of the HCV quasispecies after the initial 2 months of IFN therapy.

To investigate the role of hepatitis C virus (HCV) quasispecies mutation in the pathogenesis of HCV infection, we analyzed changes in the genetic diversity of HCV genomes in 22 patients before and after liver transplantation by using heteroduplex mobility assay (HMA) technology. All patients were infected with HCV genotype 1 and developed high-titer posttransplant viremia. Each patient was classified according to the severity of posttransplant hepatitis, as assessed by standard biochemical and histological criteria. HCV quasispecies were characterized by HMA analysis of eight separate subgenomic regions of HCV, which collectively comprise 44% of the entire genome. The glycoprotein genes E1 and E2, as well as the nonstructural protein genes NS2 and NS3, had the greatest genetic divergence after liver transplantation (the change in the heteroduplex mobility ratio [HMR] ranged from 2.5 to 7.0%). In contrast, genes encoding the core, NS4, and NS5b proteins had the least amount of genetic divergence after liver transplantation (range, 0.3 to 1.2%). The E1/E2 region showed the greatest change in genetic diversity after liver transplantation, and the change in HMRs was 2.5- to 3.3-fold greater in patients with asymptomatic or moderate disease than in those with severe disease. The E1-5' region of HCV quasispecies isolated from patients in the asymptomatic group had a significantly greater degree of diversification after liver transplantation than the same regions of HCV quasispecies isolated from patients in the severe disease group (P = 0.05). While changes in the genetic diversity of some nonstructural genes were also greater in asymptomatic patients or in patients with mild disease than in patients with severe disease, the results were not significant. Data from this cohort demonstrate that greater rates of HCV quasispecies diversification are associated with mild or moderate liver disease activity in this immunosuppressed population.

To study hepatitis C virus (HCV) genetic mutation during interferon (IFN) therapy, the temporal changes in HCV quasispecies heterogeneity were compared before and after treatment for nine patients infected with HCV genotype 1, including four nonresponders, four responders who relapsed after therapy, and one responder who experienced a breakthrough of viremia during therapy. Nine untreated patients with an average time between specimens of 8.4 years served as controls. Sequences from the second envelope glycoprotein gene hypervariable region 1 (HVR1) and the putative IFN sensitivity-determining region (ISDR) of the nonstructural NS5A gene were analyzed by heteroduplex mobility assays and nucleotide sequencing. A strong positive correlation was found between the percent change in a heteroduplex mobility ratio (HMR) and percent change in nucleotide sequence (r = 0.941, P < 0.001). The rate of fixation of mutations in the HVR1 was significantly higher for IFN-treated patients than for controls (6.97 versus 1.31% change in HMR/year; P = 0.02). Similarly, a higher rate of fixation of mutations was observed in the ISDR for IFN-treated patients than for untreated controls, although the result was not significant (1.45 versus 0.15 amino acid changes/year; P = 0.12). On an individual patient basis, IFN therapy was associated with measurable HVR1 and ISDR mutation in nine of nine (100%) and two of nine (22.2%) patients, respectively. Evolution to IFN-resistant ISDR sequences was observed in only one of nine IFN-treated patients. These data suggest that IFN therapy frequently exerts pressure on the HCV envelope region, while pressure on the ISDR was evident in only a subset of patients. Thus, the selection pressures evoked on HCV genotype 1 quasispecies during IFN therapy appear to differ among different patients.

Previous studies from Japan have described an association between a conserved sequence within the hepatitis C virus (HCV) genome and resistance to interferon (IFN) therapy for patients infected with HCV genotype 1b [Enomoto et al. (1995): Journal of Clinical Investigation 96: 224-230; Enomoto et al. (1996): New England Journal of Medicine 334:77-81]. The present study examines amino acid sequences surrounding the putative Interferon Sensitivity Determining Region (ISDR) of the NS5A gene of HCV in 21 North American patients with genotype 1a or 1b infection receiving recombinant IFN therapy. The ISDR consensus or intermediate pattern was observed in 13 of 14 NS5A clones from North American patients infected with genotype 1b. However, we found no evidence of the consensus ISDR sequence in any NS5A clones isolated from 15 patients with genotype 1a infection. In select cases, gel shift analysis showed no significant changes in the clonal frequency of the putative ISDR domain of HCV genotype 1a or 1b infected patients who were either nonresponsive to IFN therapy, or relapsed following withdrawal of IFN therapy. These results suggest that a conserved ISDR domain is neither associated with, nor responsible for, IFN resistance in North American patients infected with HCV genotype 1a, and demonstrate a need for further investigation into the reported association between ISDR consensus sequences and IFN resistance in genotype 1b clones.

Although nonverbal cues of dominance and the emotional responses they elicit have been well known since antiquity, the facial displays associated with successful political leadership have a direct political impact on the electorate in the television age. The effects of these stimuli can be studied experimentally from the perspective of human ethology. Recent findings indicate that expressive displays like those of nonhuman primates have similar effects when exhibited by human leaders in France and the United States but that cultural differences in expected behavior may significantly modify their effects., (Copyright © 1989. Published by Elsevier B.V.)