Flue gas desulfurization gypsum: implication for runoff and nutrient losses associated with broiler litter use on pastures on ultisols.

Gypsum has been shown to reduce runoff on soils prone to crust formation in the southeastern United States. Increased infiltration from gypsum applications could therefore help reduce runoff P and other nutrient losses from application of broiler litter (BL), a nutrient-rich fertilizer. In rainfall simulation experiments in June 2009 and May 2011, runoff and nutrient (N, P, Ca, Mg) losses in runoff were compared among treatments consisting of 0, 2.2, 4.5, and 9.0 Mg ha flue gas desulfurization gypsum (FGDG) combined with 13.5 Mg ha of BL and two control treatments of (0-0) and (9.0-0.0) Mg ha (FGDG-BL). A randomized block design with three replications was set up on a Cecil (Typic Kanhapludult) soil growing Coastal bermudagrass ( L.) for hay near Watkinsville, Georgia. Amendments were applied each April from 2009 to 2011. A reduction in runoff of 30% each year from the (9.0-13.5) compared with the (0-0) treatment was not statistically significant. Gypsum was effective in reducing concentration and load in one of the two study years: P and NH-N in 2009 (up to 83%) and NO-N in 2011 (up to 73%). A combination of factors related to weather extremes, timing of FGDG and BL applications, and their implication on soil and vegetation responses at different landscape positions might have caused the different responses between years. Additional studies focused on isolating the impacts of such factors would be helpful to ascertain the effectiveness of multiyear applications of FGDG as a best management practice to reduce P and other nutrient losses in soils of the southeastern United States.

Survival dynamics of fecal bacteria in ponds in agricultural watersheds of the Piedmont and Coastal Plain of Georgia.

Animal agriculture in watersheds produces manure bacteria that may contaminate surface waters and put public health at risk. We measured fecal indicator bacteria (commensal Escherichia coli and fecal enterococci) and manure pathogens (Salmonella and E. coli 0157:H7), and physical-chemical parameters in pond inflow, within pond, pond outflow, and pond sediments in three ponds in agricultural watersheds. Bishop Pond with perennial inflow and outflow is located in the Piedmont, and Ponds A and C with ephemeral inflow and outflow in the Coastal Plain of Georgia. Bromide and chloride tracer experiments at Bishop Pond reflected a residence time much greater than that estimated by two models, and indicated that complete mixing within Bishop Pond was never obtained. The long residence time meant that fecal bacteria were exposed to solar UV-radiation and microbial predation. At Bishop Pond outflow concentrations of fecal indicator bacteria were significantly less than inflow concentrations; such was not observed at Ponds A and C. Both Salmonella and E. coli 0157:H7 were measured when concomitant concentrations of commensal E. coli were below the criterion for surface water impairment indicating problems with the effectiveness of indicator organisms. Bishop Pond improved down stream water quality; whereas, Ponds A and C with ephemeral inflow and outflow and possibly greater nutrient concentrations within the two ponds appeared to be less effective in improving down stream water quality.

Runoff water quality during drought in a zero-order georgia piedmont pasture: nitrogen and total organic carbon.

Approximately 11% of the Southern Piedmont (1.8 million ha) is used for pasture and hay production, mostly under low-input management. Few studies have investigated in the region long-term nitrogen and carbon losses in surface runoff, which can be significant. We present 1999 to 2009 hydrologic and water quality data from a rotationally grazed, 7.8-ha, zero-order pasture (W1) near Watkinsville in the Georgia Piedmont. Annual rainfall was 176 to 463 mm below the long-term average (1240 mm) in 7 of the 11 yr. There were 20 runoff events during 86 mo of below-average rainfall (deficit period), compared with 54 events during 46 mo of nondeficit period. Mean event flow-weighted concentration (in mg L) was 0.96 for nitrate-nitrogen (NO-N), 0.97 for ammonium-nitrogen (NH-N), 3.70 for total nitrogen (TN), and 9.12 for total organic carbon (TOC) ( = 43-47; limited due to instrument problem). Nutrient loads (in kg ha per event) averaged 0.04 for NO-N, 0.03 for NH-N, 0.19 for TN, and 0.54 for TOC. Total loads for N and TOC were 6 to 11 times greater from nondeficit than from deficit periods. The observed N concentrations, while well below maximum drinking water standard limits, could pose risk for eutrophication, which can be stimulated at lower concentrations. However, the ability of headwater streams, such as the one downstream of W1, to reduce nutrient concentrations might partially alleviate this concern. The results of this study point to the need to use a long-term dataset that includes measurements made in drought and wet years when evaluating the efficacy of water quality standards.

Comparative die-off of Escherichia coli O157:H7 and fecal indicator bacteria in pond water.

In situ and in vitro experiments were performed to assess the effects of solar radiation and predation by indigenous microflora on the relative die-off rates of a toxigenic strain of Escherichia coli O157:H7, commensal E. coli, and fecal enterococci in surface waters from ponds in agricultural watersheds. The objective of these experiments was to discern a mechanism of persistence of E. coli O157:H7 in surface waters compared to fecal indicator bacteria. Results of these experiments indicated that E. coli and fecal enterococci were affected by both insolation and apparent predation; whereas E. coli O157:H7 appeared to be resistant to both of these environmental stressors. The number of days to reach 99% die-off (T(99)-values) for E. coli O157:H7 was significantly greater than that for the indicator bacteria. The capacity to prolong die-off may be connected to the apparent persistence of E. coli O157:H7 in surface waters.

Single and combination diagnostic test efficiency and cost analysis for detection and isolation of avian influenza virus from wild bird cloacal swabs.

Effective laboratory methods for identifying avian influenza virus (AIV) in wild bird populations are crucial to understanding the ecology of this pathogen. The standard method has been AIV isolation in chorioallantoic sac (CAS) of specific-pathogen-free embryonating chicken eggs (ECE), but in one study, combined use of yolk-sac (YS) and chorioallantoic membrane inoculation routes increased the number of virus isolations. In addition, cell culture for AIV isolation has been used. Most recently, real-time reverse transcriptase (RRT)-PCR has been used to detect AIV genome in surveillance samples. The purpose of this study was to develop a diagnostic decision tree that would increase AIV isolations from wild bird surveillance samples when using combinations of detection and isolation methods under our laboratory conditions. Attempts to identify AIV for 50 wild bird surveillance samples were accomplished via isolation in ECE using CAS and YS routes of inoculation, and in Madin-Darby canine kidney (MDCK) cells, and by AIV matrix gene detection using RRT-PCR. AIV was isolated from 36% of samples by CAS inoculation and 46% samples by YS inoculation using ECE, isolated from 20% of samples in MDCK cells, and detected in 54% of the samples by RRT-PCR. The AIV was isolated in ECE in 13 samples by both inoculation routes, five additional samples by allantoic, and 10 additional samples by yolk-sac inoculation, increasing the positive isolation of AIV in ECE to 56%. Allantoic inoculation and RRT-PCR detected AIV in 14 samples, with four additional samples by allantoic route alone and 13 additional samples by RRT-PCR. Our data indicate that addition of YS inoculation of ECE will increase isolation of AIV from wild bird surveillance samples. If we exclude the confirmation RT-PCR test, cost analysis for our laboratory indicates that RRT-PCR is an economical choice for screening samples before doing virus isolation in ECE if the AIV frequency is low in the samples. In contrast, isolation in ECE via CAS and YS inoculation routes without prescreening by RRT-PCR was most efficient and cost-effective if the samples had an expected high frequency of AIV.

Rainfall and tillage effects on transport of fecal bacteria and sex hormones 17beta-estradiol and testosterone from broiler litter applications to a Georgia Piedmont Ultisol.

Poultry litter provides nutrients for crop and pasture production; however, it also contains fecal bacteria, sex hormones (17beta-estradiol and testosterone) and antibiotic residues that may contaminate surface waters. Our objective was to quantify transport of fecal bacteria, estradiol, testosterone and antibiotic residues from a Cecil sandy loam managed since 1991 under no-till (NT) and conventional tillage (CT) to which either poultry litter (PL) or conventional fertilizer (CF) was applied based on the nitrogen needs of corn (Zea mays L) in the Southern Piedmont of NE Georgia. Simulated rainfall was applied for 60 min to 2 by 3-m field plots at a constant rate in 2004 and variable rate in 2005. Runoff was continuously measured and subsamples taken for determining flow-weighted concentrations of fecal bacteria, hormones, and antibiotic residues. Neither Salmonella, nor Campylobacter, nor antimicrobial residues were detected in litter, soil, or runoff. Differences in soil concentrations of fecal bacteria before and after rainfall simulations were observed only for Escherichia coli in the constant rainfall intensity experiment. Differences in flow-weighted concentrations were observed only for testosterone in both constant and variable intensity rainfall experiments, and were greatest for treatments that received poultry litter. Total loads of E. coli and fecal enterococci, were largest for both tillage treatments receiving poultry litter for the variable rainfall intensity. Load of testosterone was greatest for no-till plots receiving poultry litter under variable rainfall intensity. Poultry litter application rates commensurate for corn appeared to enhance only soil concentrations of E. coli, and runoff concentrations of testosterone above background levels.

Variation in Ruminant Preference for Alfalfa Hays Cut at Sunup and Sundown.

Diurnal variation in the concentration of total nonstructural carbohydrates (TNC) occurs in plants as a result of photosynthesis. Ruminants have been shown to prefer tall fescue (Festuca arundinacea Schreber) hays cut in the afternoon but the effect of morning vs. evening cutting had not been tested in legumes. To test for diurnal variation in preference for alfalfa (Medicago sativa L.), we harvested six times in the midbud stage. Harvests were paired so that each time a cutting of alfalfa was made at sundown (PM) another was made the next morning at sunup (AM). We harvested in this manner three times resulting in six hays. The hays were field dried, baled, and chopped prior to their use 3 to 6 mo after harvest. Three experiments were conducted [Exp. 1, sheep (Ovis aries); Exp. 2, goats (Capra hircus hircus); and Exp. 3, cattle (Bos taurus)] utilizing six animals in each case. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (15 pairs) was presented for a meal. Data were analyzed by multidimensional scaling as well as by traditional analyses. Multidimensional scaling indicated that the animals were basing selection on at least two criteria. Variables associated with preference through multiple regression varied across experiments but significant coefficients were found between preference and nitrate, protein, carbohydrate fractions, lignin, and cellulose. Coefficients varied depending on which other variables were in the model; however, carbohydrates were associated with positive coefficients. Shifting hay mowing from early in the day to late in the day was effective in increasing forage preference as expressed by short-term dry matter intake.