Swine Lagoon Effluent Research Articles

Evaluation of five bermudagrass cultivars fertigated with swine lagoon effluent

AbstractBermudagrass [Cynodon dactylon (L.) Pers.] hay is an important output from land receiving swine (Sus scrofa) effluent application (also known as spray fields); however, there is limited information about cultivar differences in the upper Southeast United States. Herbage accumulation, nutritive value, tissue nitrate concentration, and stem maggot damage were evaluated for five bermudagrass cultivars (‘Coastal’, ‘Midland 99’, ‘Ozark’, ‘Tifton 44’, and ‘Tifton 85’) fertigated with swine effluent throughout three growing seasons (2016, 2017, and 2018). All cultivars achieved canopy height ≥35 cm by July and cover of 100% by August of year of planting. Based on 3‐yr averages, Tifton 85 (9.3 Mg ha–1) had greater herbage accumulation than cultivars Coastal, Ozark, and Tifton 44 (≈7.9 Mg ha–1), and Midland 99 was intermediate (8.5 Mg ha–1). Bermudagrass stem maggot (Atherigona reversura) damage was consistently lower for Tifton 85 and resulted in larger differences in herbage accumulation in 2017 (11.2 vs. 8.4 Mg ha–1 for Tifton 85 and the other cultivars, respectively). There were moderate differences in crude protein concentration (ranged from 179 to 212 g kg–1) and no difference in total digestible nutrients (622 g kg–1). Tissue nitrate concentrations ranged from 3,433 to 16,168 mg NO3– kg–1. Differences in productivity and nutritive value were moderate among cultivars; however, in areas with potentially high bermudagrass stem maggot damage, greater utilization of Tifton 85, if adapted, is warranted. Hay production from spray fields results in high yields and high nutritive value forage. Frequent nitrate testing, if possible by harvested hay lot, is advised.

Effect of controlled drainage on nitrogen fate and transport for a subsurface drained grass field receiving liquid swine lagoon effluent

Application of livestock manure has become a principal nutrient source in groundwater and surface water. The goal of this research was to investigate the effect of controlled drainage (CD) on nitrogen (N) fate and transport for a subsurface drained grass field receiving liquid swine lagoon effluent (SLE). A four-year field experiment was conducted on a naturally poorly drained pasture in eastern North Carolina. The 1.25 ha experimental field was artificially drained by subsurface drains installed at 1.0 m depth and 12.5 m spacing. Two treatments, replicated twice were implemented: conventional drainage (FD) and CD. The CD management protocol was more intensive compared to previous studies. The drain outlets of CD plot were set at 36 cm below soil surface all year round except several days before irrigation application when water table depth was shallower than 65 cm below surface. Controlled drainage significantly reduced drainage flow and TN loading via subsurface drain lines by an average of 397 mm yr−1 (93%) and 34.5 kg N ha−1 yr−1 (94%), respectively. DRAINMOD hydrologic simulations indicated that 96% of the reduction in predicted drain flow was attributed to increased lateral seepage. The nitrogen that did not drain from the field in response to CD was lost via enhanced denitrification (67%) and lateral seepage to adjacent fields (33%). This study clearly demonstrated how CD management affects the N fate and transport through seepage and denitrification process.

Biomass and Sweet Sorghum Fertilized with Swine Lagoon Effluent for Bioenergy

Core Ideas Dry matter yields were not different between the two sorghums in 11 out of 12 yr–location combinations. Nitrogen, P, and K removals averaged 138, 28, and 313 kg ha–1, respectively. Both sorghum cultivars, ES5200 and M81‐E, were productive biomass crops at swine spray fields and may be a feasible alternative for producers that desire the flexibility of an annual crop and high dry matter yields in a single clipping event at the end of the growing season (15.7 ± 5.1 Mg ha–1 yr–1. Land receiving waste effluent from swine (Sus scrofa domesticus) production systems (also known as spray fields) may provide a unique opportunity for bioenergy feedstock supply from sorghum [Sorghum bicolor (L.) Moench]. Information on dry matter (DM) production and nutrient uptake from on‐farm trials is needed to determine the viability of this practice. The objectives of the study were to compare DM production and nutrient removal of two sorghum cultivars (high biomass Blade ES5200 and sweet sorghum M81‐E) planted at three on‐farm swine effluent spray field locations. The study was conducted in North Carolina for 4 yr (2012–2015). Dry matter yields ranged from 8.1 to 27.7 Mg ha−1 and were no different between sorghum entries in 11 out of 12 location‐year combinations. Nitrogen concentration in the plant tissue ranged from 5.9 to 12.9 g kg−1 reflecting the wide range of N loadings (41–624 kg ha−1). Nitrogen removal ranged from 54 to 287 kg ha−1. Phosphorus concentration in the plant tissue ranged from 1.4 to 2.5 g kg−1 and removal ranged from 15.4 to 51.3 kg ha−1. Potassium concentration and removal were not different between entries and averaged 20.4 g kg−1 and 313 kg ha−1, respectively. The results indicate that if sorghum is to be the only crop per annual cycle, then irrigation management and nutrient loading need to be less intensive (lower amounts), specially for N and K, than in current bermudagrass (Cynodonon dactylon L.)‐based systems to prevent soil nutrient accumulation.

Yield and Nutrient Removal by Bioenergy Grasses on Swine Effluent Spray Fields in the Coastal Plain Region of North Carolina

Bioenergy grasses such as giant miscanthus (Miscanthus × giganteus) and switchgrass (Panicum virgatum L.) are promising alternatives to the traditional coastal bermudagrass [Cynodon dactylon (L.) Pers.] at spray fields in Eastern North Carolina. The objective of this study was to determine the impact of different harvest practices on yield and nutrient removal of miscanthus and switchgrass in a swine (Sus scrofa domesticus) lagoon effluent spray field environment. Field trials of grasses under six single-cut and double-cut harvest practices (May/October, June/October, July/October, Aug/October, October only, and December only) were established at three commercial swine farms in Eastern North Carolina in either 2011 or 2012. Throughout the 4-year experimental period (2012–2015), both miscanthus and switchgrass produced significantly higher biomass yield than coastal bermudagrass. Two-cut harvest systems significantly improved the yields of miscanthus and switchgrass relative to a single harvest in December at spray fields. The maximum yields were 24 Mg ha−1 year−1 for miscanthus and 18 Mg ha−1 year−1 for switchgrass. Bioenergy grasses removed more nutrients under two-cut systems than under a single harvest. The significantly greater nutrient removals under two-cut harvest systems would result in lower requirements for receiver crop acreage and are more desirable from a spray field nutrient management perspective.

Short-term and seasonal soil nitrogen dynamics and recovery by bermudagrass irrigated with 15N labelled swine lagoon effluent

Aim Rapid and efficient utilization of swine (Sus scrofa domestucus) lagoon effluent nitrogen (N) by crops is necessary to minimize N losses and environmental pollution. The objective of this study was to determine the dynamics and fate of effluent N applied to bermudagrass (Cynodon dactylon (L.) pers.) using 15N tracer technology as influenced by irrigation date.

Decay rates of zoonotic pathogens and viral surrogates in soils amended with biosolids and manures and comparison of qPCR and culture derived rates

AimsThe purpose of this study was to establish inactivation decay constants of foodborne pathogens and coliphage in clay and sandy soils for future "downstream" analyses such as quantitative microbial risk analysis and to compare cultivation-dependent and -independent (e.g. qPCR) methods. Methods and resultsSalmonella enterica, Campylobacter jejuni, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium perfringens, were seeded together with MS2 and ØX174 phages, into three waste matrices (Class B biosolids, swine lagoon effluent, cattle manure), and phosphate buffered saline (PBS) as a control, and applied to two soil types (sandy loam, clay loam) using two management practices (incorporated, surface applied). S. enterica and L. monocytogenes inactivation rates were positively affected (e.g. slower rate) by solid wastes, while C. jejuni was quickly inactivated by day 7 regardless of waste type. The use of qPCR provided more conservative inactivation rates, with qPCR-based rates typically twice as slow as cultivation-based. The effect of soil type and management were less apparent as rates were variably affected. For instance, incorporation of waste negatively impacted (e.g. faster rate) inactivation of Salmonella when measured by qPCR, while the opposite was true when measured by cultivation. Inactivation rates were organism∗waste∗soil∗management dependent since the interactions of these main effects significantly affected most combinations. ConclusionsClass B biosolids and cattle manure most often slowed inactivation when measured by cultivation, but the complex interactions between variables and organism made sweeping conclusions difficult. On the contrary cultivation-independent inactivation rates were negatively affected by solid wastes. Inactivation rates developed by cultivation-dependent and -independent assays needs further scrutiny as interprerations can vary by orders of magnitude depending on the organism∗environment combination. Significance and impact of the studyThis study compares decay rate data based on waste, soil, management and assay type which can be further used in risk assessments.

Effects of reclaimed water matrix on fate of pharmaceuticals and personal care products in soil

Reclaimed water is increasingly used to supplement water resources. However, reclaimed water has a complex matrix, which includes emerging chemical contaminants, that is introduced to the soil when this water is used for irrigation. The effects of microbial activity, dissolved matter, nutrients, and particulate matter in reclaimed water on half-life of 11 pharmaceutical and personal care products (PPCPs) in soil were investigated with 7 treatment waters, namely swine lagoon effluent (either unaltered, sterilized, or filtered and sterilized) and nanopure water (either unaltered or with added nitrogen, phosphorus, or potassium). The extractable residues of the parent PPCPs were measured over 35 d. Lagoon microbial activity was significantly (p ≤ 0.05) related to increased half-life of 4 PPCPs (carbamazepine, fluoxetine, ibuprofen, sulfamethoxazole) by 14–74%, and to decreased half-life of 3 others (caffeine, gemfibrozil, naproxen) by 13–25%. The presence of lagoon dissolved matter was significantly correlated with a 20–110% increase in half-life for 6 PPCPs (caffeine, estrone, gemfibrozil, ibuprofen, naproxen, triclocarban). However, lagoon particulate matter was significantly correlated with 9–52% decrease in half-life for these same compounds, as well as trimethoprim. The levels of nitrogen, phosphorous, and potassium in the lagoon effluent were not significantly related to half-life for most PPCPs, except caffeine. Overall, specific components of reclaimed water matrix had different effects on the soil half-lives of PPCPs, suggesting that the composition of reclaimed water needs to be considered when evaluating PPCP fate after land application.

Using broiler litter and swine manure lagoon effluent in sawdust-based swine mortality composts: Effects on nutrients, bacteria, and gaseous emissions

Disposition of mortalities challenges confined animal feeding operations (CAFOs), especially sow (farrowing) farms, which experience mortalities daily. Regulations and transportation costs may preclude incineration, landfill burial, and rendering; therefore, swine CAFOs in Mississippi in the Mid-South U.S. often compost mortalities. In this study, a farm-standard composting mix of sawdust (S) and water (W) was compared with mixes where N was supplied by broiler litter (L) and water was replaced with swine lagoon effluent (E). The objective was to assess the effects of these manure byproducts: 1) on nutrients and bacteria in composts destined for land application; and 2) on emissions of ammonia and greenhouse gases. Three replications of four mixes (SW, SLW, SE, SLE) were compared in microcosms comprising modified plastic recycling bins. The experiment was repeated three times in different seasons in one year. Mixes were compared for differences in temperature, water content, nutrients (C, N, P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn), bacteria (Gram−, Gram+, Clostridium perfringens, Salmonella, Listeria, Escherichia coli), and emissions (NH3, CO2, CH4, N2O). Litter addition increased composting temperatures initially and after aerations; increased nutrient concentrations, except C, in start mixes and all except C and N, in finish mixes; increased Gram+ bacteria, Salmonella, and E. coli in start mixes, but only Gram+s in finish mixes; and increased emissions. Effluent addition increased early composting temperatures; had no effect on nutrients or bacteria, except increased C. perfringens in start, but not finish mixes; and had no effect on emissions. Nutrients in finish composts did not differ among mixes for N (average 3.3%), but litter composts had more P and K, and lower N:P than composts without litter. Improving mortality composting is of global importance as increasing livestock populations and intensive animal production systems require practical, safe, environmentally sound disposal of carcasses.

Microbial Community Structure Across a Wastewater-Impacted Riparian Buffer Zone in the Southeastern Coastal Plain

Riparian buffer zones are important for both natural and developed ecosystems throughout the world because of their ability to retain nutrients, prevent soil erosion, protect aquatic environments from excessive sedimentation, and filter pollutants. Despite their importance, the microbial community structures of riparian buffer zones remains poorly defined. Our objectives for this study were twofold: first, to characterize the microbial populations found in riparian buffer zone soils; and second, to determine if microbial community structure could be linked to denitrification enzyme activity (DEA). To achieve these objectives, we investigated the microbial populations of a riparian buffer zone located downslope of a pasture irrigated with swine lagoon effluent, utilizing DNA sequencing of the 16S rDNA, DEA, and quantitative PCR (qPCR) of the denitrification genes nirK, nirS, and nosZ. Clone libraries of the 16S rDNA gene were generated from each of twelve sites across the riparian buffer with a total of 986 partial sequences grouped into 654 operational taxonomic units (OTUs). The Proteobacteria were the dominant group (49.8% of all OTUs), with the Acidobacteria also well represented (19.57% of all OTUs). Analysis of qPCR results identified spatial relationships between soil series, site location, and gene abundance, which could be used to infer both incomplete and total DEA rates.

Distribution of ten antibiotic resistance genes in E. coli isolates from swine manure, lagoon effluent and soil collected from a lagoon waste application field

The prevalence of ten antibiotic resistance genes (ARGs) was evaluated in a total of 616 Escherichia coli isolates from swine manure, swine lagoon effluent, and from soils that received lagoon effluent on a commercial swine farm site in Sampson County, North Carolina (USA). Isolates with ARGs coding for streptomycin/spectinomycin (aadA/strA and strB), tetracycline (tetA and tetB), and sulfonamide (sul1) occurred most frequently (60.6-91.3%). The occurrence of E. coli isolates that carried aadA, tetA, tetB, and tetC genes was significantly more frequent in soil samples (34.0-97.2%) than in isolates from lagoon samples (20.9-90.6%). Furthermore, the frequency of isolates that contain genes coding for aadA and tetB was significantly greater in soil samples (82.6-97.2%) when compared to swine manure (16.8-86.1%). Isolates from the lagoon that carried tetA, tetC, and sul3 genes were significantly more prevalent during spring (63.3-96.7%) than during winter (13.1-67.8%). The prevalence of isolates from the lagoon that possessed the strA, strB, and sul1 resistance genes was significantly more frequent during the summer (90.0-100%) than during spring (66.6-80.0%). The data suggest that conditions in the lagoon, soil, and manure may have an impact on the occurrence of E. coli isolates with specific ARGs. Seasonal variables seem to impact the recovery isolates with ARGs; however, ARG distribution may be associated with mobile genetic elements or a reflection of the initial numbers of resistant isolates shed by the animals.

Comparison of Selected Nutrients and Bacteria from Common Contiguous Soils Inside and Outside Swine Lagoon Effluent Spray Fields after Long‐Term Use

Swine (Sus scofa domestica) lagoon effluent is a valuable resource. In the U.S. Mid-South it is applied from April to September to fertilize grass hay in spray-irrigated fields. Lagoon levels of nutrients and bacteria, and soil levels of nutrients have been documented, but little was known of effluent bacterial levels in soil. The present study examined levels of selected effluent bacteria and nutrients in soils inside and outside spray fields after >15 yr of effluent irrigation. Samples were collected February to March 2009 from contiguous soils spanning adjacent irrigated and nonirrigated areas. Separate soil cores for bacterial and nutrient tests were collected in pairs <10 cm apart. Five cores each were collected at 15-m intervals and combined, respectively, to comprise inside and outside samples from each of 20 soils (four each from five farms/spray fields). Analyses of data combined across all soils showed higher pH and Mehlich-3-extracrable (M3-) P, Mg, K, Na, Cu, and Zn inside than outside spray fields, while total N, total C, M3-Ca, and M3-Mn did not differ. Bacterial levels were higher inside than outside spray fields for heterotrophic plate counts, thermotolerant coliforms, Staphylococcus spp., and Clostridium perfringens, but levels of Escherichia coli and Enterococcus spp. were not different. Cultural presence/absence tests for three pathogens (Listeria spp., Campylobacter spp., and Salmonella spp.) detected only Listeria spp., which did not differ inside (23% positive samples) and outside (28% positive). Molecular tests detected all three pathogens at low levels that were not different inside and outside. We found no evidence of cumulative buildup of Campylobacter spp., Listeria spp., or Salmonela s. in spray field soils.

Economic Profitability of Sustained Application of Swine Lagoon Effluent and Beef Feedlot Manure Relative to Anhydrous Ammonia in the Oklahoma Panhandle

With the rapid growth of swine (Sus scrofa domestica) production in the Oklahoma Panhandle, animal waste management has become a growing concern. Field experiments were conducted to evaluate the long‐term effects of equivalent nitrogen rates of swine lagoon effluent (SE), beef manure (BM), and commercial fertilizer on the yield and economic returns of irrigated corn (Zea mays L.) grown on calcareous Gruver silt loam soil (fine, mixed, superactive, mesic Aridic Paleustoll) near Goodwell, Oklahoma. A randomized, complete‐block, split‐plot design with three replications was used to test the main effects of N source (NS) and equivalent N application rates (NR) of 56, 168, and 504 kg N ha−1 Both BM and SE generated significantly (P &lt; 0.05) higher corn yields than anhydrous ammonia (AA) across the main effect of NS. Greater separation of mean corn yields was found among NS as the equivalent NR rate was increased from 56 to 504 kg N ha−1 with the following rankings (P &lt; 0.05): AA = BM = SE at 56 kg N ha−1, BM = AA ≥ SE at 168 kg N ha−1, and SE &gt; BM &gt; AA at 504 kg N ha−1 Both SE and BM generated significantly (P &lt; 0.05) higher economic returns than AA. The highest ranked alternatives of economic returns were generated by SE×504 and BM×168. Results indicate that SE and BM can be economically viable substitutes for commercial fertilizer, bringing higher yields and economic benefits to producers in the Oklahoma Panhandle.

Sorption of Phosphorus from Swine, Dairy, and Poultry Manures

In most phosphorus (P) sorption studies, P is added as an inorganic salt to a predefined background solution such as calcium chloride (CaCl2) or potassium chloride (KCl); however, in many regions, the application of P to agricultural fields is in the form of animal manure. The purpose of this study, therefore, was to compare the sorption behavior of dissolved reactive P (DRP) in monopotassium phosphate (KH2PO4)–amended CaCl2 and KCl solutions with sorption behavior of DRP in three different animal manure extracts. Phosphorus single‐point isotherms (PSI) were conducted on eight soils with the following solutions: KH2PO4‐amended 0.01 M CaCl2 solution, KH2PO4‐amended 0.03 M KCl solution, water‐extracted dairy manure, water‐extracted poultry litter, and swine lagoon effluent. The PSI values for the dairy manure extract were significantly lower than the CaCl2 solution for all eight soils and lower than the KCl solution for six soils. The PSI values were significantly higher, on the other hand, for poultry litter extract and swine effluent than the inorganic solutions in four and five of the soils, respectively. Our observations that the sorption of DRP in manure solutions differs significantly from that of KH2PO4‐amended CaCl2 and KCl solutions indicates that manure application rates based on sorption data collected from inorganic P salt experiments may be inaccurate.

Soil nutrient evaluation from swine effluent application to five forage-system practices

Many contract swine producers are located in the southeastern U.S. In this region almost all of the swine effluent from swine production is applied to warm-season perennial species such as bermudagrass [Cynodon dactylon (L.) Pers.] which is widely grown for summer grazing and hay production. A 3-yr study was conducted to investigate the impact of forage double-cropping on nutrient accumulation and leaching in Mantachie fine loam soil fertilized with swine (Sus scrofa domesticus) lagoon effluent as the source of plant nutrients. Plots of previously established Tifton 44 bermudagrass were overseeded in the fall with one of four winter annuals: berseem clover (Trifolium alexandrinum L.); crimson clover (T. incarnatum L.); ryegrass (Lolium multiflorum L.); or wheat (Triticum aestivum L.). Four plots of bermudagrass were not overseeded and considered as control. Plots were harvested in spring for cool-season annual hay and in summer for bermudagrass hay. Swine effluent was applied during spring and summer on a need base. Suction lysimeters were installed in selected plots at two depths to monitor nutrient leaching. Surface soil samples were taken to determine baseline nutrient contents, followed by three other sampling dates during the study. Bermudagrass dry matter production (3-yr average = 9.8 Mg ha−1) was not adversely affected by the overseeding treatments. Greatest dry matter production was achieved with bermudagrass overseeded with ryegrass (3-yr average = 11.3 Mg ha−1). Soil pH decreased by almost one unit by the end of the study. While total P (TP) did not change much, Mehlich-3 P (M3-P), K, Cu, and Zn increased significantly, Mg and Mn concentrations decreased by 2002 compared to the baseline levels. Soil P, Mg, K, Fe, Mn, and Zn accumulation were greater under bermudagrass/wheat combination. In general, the influence of double cropping on soil nutrient accumulation was not conclusive, however, this practice provides the year-round green forage for grazing and haying. Nutrient concentrations in soil and lysimeter leachate were directly related to the quantity of effluent applied. Results also demonstrated that effluent application must be coordinated with the nutrient requirements of the growing forages in order to minimize accumulation and leaching.

EPA Worst Case Water Microcosms for Testing Phage Biocontrol of Salmonella

A microplate method was developed as a tool to test phages for their ability to control Salmonella in aqueous environments. The method used EPA (U.S. Environmental Protection Agency) worst case water (WCW) in 96-well plates. The WCW provided a consistent and relatively simple defined turbid aqueous matrix, high in total organic carbon (TOC) and total dissolved salts (TDS), to simulate swine lagoon effluent, without the inconvenience of malodor and confounding effects from other biological factors. The WCW was originally defined to simulate high turbidity and organic matter in water for testing point-of-use filtration devices. Use of WCW to simulate lagoon effluent for phage testing is a new and innovative application of this matrix. Control of physical and chemical parameters (TOC, TDS, turbidity, temperature, and pH) allowed precise evaluation of microbiological parameters (Salmonella and phages). In a typical application, wells containing WCW were loaded with Salmonella enterica susp. enterica serovar Typhimurium (ATCC14028) and treated with phages alone and in cocktail combinations. Mean Salmonella inactivation rates (k, where the lower the value, the greater the inactivation) of phage treatments ranged from -0.32 to -1.60 versus -0.004 for Salmonella controls. Mean log(10) reductions (the lower the value, the greater the reduction) of Salmonella phage treatments were -1.60 for phage PR04-1, -2.14 for phage PR37-96, and -2.14 for both phages in a sequential cocktail, versus -0.08 for Salmonella controls. The WCW microcosm system was an effective tool for evaluating the biocontrol potential of Salmonella phages.

Soil enzyme activities in two forage systems following application of different rates of swine lagoon effluent or ammonium nitrate

Land application of swine lagoon effluent (SLE) to forage production systems is widespread in the southeastern USA and often leads to change in soil properties. Although soil enzymes are crucial to the degradation of soil organic matter and cycling of nutrients, the impacts of SLE application on soil enzyme activities have not been well characterized. We assessed the activities of soil enzymes involved in soil C, N, and P cycling in forage systems 3 years after the termination of three consecutive years of fertilization. Bermudagrass and tall fescue were supplied with SLE or ammonium nitrate (AN) at the rates of 0, 200, 400, and 600 kg plant available N (PAN) ha −1 year −1. The activities of oxidative enzymes (i.e., peroxidase and phenol oxidase) differed between soils amended with SLE versus AN. In soils amended with AN at 600 kg PAN ha −1 year −1, the activities of phenol oxidase and peroxidase were lower than or similar to those in the unfertilized control. In contrast, those activities were stimulated by the application of SLE at the rate of 600 kg PAN ha −1 year −1 except for phenol oxidase in the bermudagrass system. The activities of cellobiohydrolase, β-glucosidase, cellulase, β-glucosaminidase, protease, and acid phosphatase, however, were independent of the source, but varied with the rate of fertilization. In general, the activities of cellobiohydrolase, β-glucosidase, cellulase, β-glucosaminidase, protease, and acid phosphatase in soils with N fertilization at 200 or 400 kg PAN ha −1 year −1 were higher than those in the unfertilized control. But the activities of some hydrolytic enzymes in soils fertilized with 600 kg PAN ha −1 year −1 were similar to or lower than those in the unfertilized control. Non-metric multidimensional scaling (NMS) analysis integrated the activities of eight soil enzymes and showed significant differences between fertilized soils and the unfertilized control and between soils amended with SLE versus AN. These differences in soil integrated enzyme activity were correlated with soil pH (Pearson's correlation coefficient r = 0.76, P < 0.05) rather than with other soil properties. The activities of individual enzymes such as peroxidase, cellulase, and acid phosphatase were also significantly correlated with soil pH. Our results suggested that fertilization-associated change in soil pH could influence the potential activities of soil enzymes in the hay production systems. Application of SLE at 600 kg PAN ha −1 year −1 may be unbeneficial to soil organic matter accumulation and nutrient cycling.

Characterization of Salmonella Bacteriophages Isolated from Swine Lagoon Effluent

Four Salmonella bacteriophages that had been originally isolated from swine manure lagoons were characterized and compared to each other and to well-known Salmonella phages P22 and Felix 01. Host ranges of the lagoon phages were similar to each other in spot tests on reference strains of Salmonella, but differed slightly from each other on a panel of Salmonella lagoon strains. In single-step growth at 35 degrees C the lagoon phages had latent periods of 15 to 20 min and burst sizes from 100 to 230. The lagoon phages and P22 were purified by cesium chloride (CsCl) gradient centrifugation and used to produce specific antisera and DNA. The lagoon phages were indistinguishable from each other but distinct from P22 and Felix 01 in immunodiffusion and infectivity neutralization tests and in restriction digest analysis.

Soil chemical and microbiological properties in hay production systems: residual effects of contrasting N fertilization of swine lagoon effluent versus ammonium nitrate

This study characterized soil chemical and microbiological properties in hay production systems that received from 0 to 600 kg plant-available N (PAN) ha−1 year−1 from either swine lagoon effluent (SLE) or ammonium nitrate (AN) from 1999 to 2001. The forage systems contained plots planted with bermudagrass (Cynodon dactylon L.) or endophyte-free tall fescue (Festuca arundinaceae Schreb.). In March 2004, the plots were sampled for measurements of a suite of soil chemical and microbiological properties. Nitrogen fertilization rates were significantly correlated with soil pH and K2SO4-extractable soil C but not with total soil C, soil C/N ratio, electrical conductivity, or Mehlich-3-extractable nutrients. Soil supplied with SLE had significantly lower Mehlich-3-extractable nutrients than the soil supplied with AN. Two indicators of soil N-supplying capacity (potentially mineralizable N and amino sugar N) varied with plant species and the type of N fertilizer. However, they generally peaked at an application rate of 200 or 400 kg PAN ha−1 year−1. Soil microbial biomass C also peaked at an application rate of 200 or 400 kg PAN ha−1 year−1. Nitrification potential was significantly higher in soil supplied with AN than in the unfertilized control but was similar between SLE-fertilized and unfertilized soils. Our results indicated that an application rate as high as 600 kg PAN ha−1 year−1 did not benefit soil microbial biomass, microbial activity, and N transformation processes in these forage systems.

Soil microbial community composition and structure: residual effects of contrasting N fertilization of swine lagoon effluent versus ammonium nitrate

Land application of swine lagoon effluent (SLE) often changes soil pH and the concentrations of nutrients and trace metals. We hypothesize that fertilization-associated alteration in soil properties would have long-lasting effects on soil microbial community and the effects would depend on fertilization rates. In this study, microbial community composition and structure were characterized with phospholipid fatty acid (PLFA) profiles. Soils (0–7.5 cm depth) were sampled in March 2004 from the field plots planted with bermudagrass and tall fescue that received 0–600 kg plant available N (PAN) ha−1 year−1 of SLE or ammonium nitrate (AN) from 1999 to 2001. We observed that PLFA profiles differed significantly (P < 0.05) between soils supplied with SLE versus AN, specifically at the highest application rate. PLFA profiles were strongly correlated with fertilization-associated changes in soil pH (Pearson’s correlation coefficient r = 0.80, P < 0.01) and Mehlich III extractable Ca (r = 0.78, P < 0.01) and Mg (r = 0.72, P < 0.01). In soils receiving 200 and 400 kg PAN ha−1 year−1 of SLE or AN, microbial community was enriched slightly with fungi (P < 0.01). In soils receiving 600 kg PAN ha−1 year−1 of SLE or AN, however, microbial community was stressed as evidenced by the reduction in microbial monounsaturated fatty acids and by the increase in the ratios of saturated-to-unsaturated fatty acids and of cyclopropyl fatty acids-to-their monoenoic precursors. These changes in PLFA biomarkers for stress were significantly (P < 0.01) correlated with soil pH and Mehlich III extractable Ca and Mg, but not with soil properties such as total soil C, soluble soil organic C, soil inorganic N or Mehlich III extractable soil P. Our results indicated that soil microbial community was negatively affected when soils received SLE at an application rate of 600 kg PAN ha−1 year−1 in this forage production system.

A Farm-Scale Test of Nitrogen Assimilation by Vegetated Buffer Systems Receiving Swine Lagoon Effluent by Overland Flow

A farm-scale study was conducted from 2000 to 2004 to determine the effectiveness of grass-forest vegetated buffers in assimilating nitrogen (N) from overland flow application of swine lagoon effluent. The rationale for the study was that replicated buffer plot studies had shown that vegetated buffers will effectively assimilate N, but it was not known whether or not they would work at a larger scale. The study was conducted on a commercial farm near Tifton, Georgia. Wastewater was pumped from a single-stage anaerobic lagoon to vegetated buffers composed of grass and mature or newly planted pines. The buffers approximated 60 m in length by 90 m in width. The upper 10 m of each buffer was in grass, while the downslope area was in mature or newly planted pines. Six buffers were instrumented for wastewater application and water quality monitoring. Two buffers received wastewater at a 1X rate (600 kg N ha-1 year-1), two at a 3/4X rate (450 kg N ha-1 year-1), and two served as controls. The wastewater was applied to the 10 m grassed portion of the buffers. Transects of shallow groundwater wells starting at the grass-forest interface and running downslope were used to monitor water quality N. The study showed mixed results concerning N assimilation by the buffers. Upslope land use changes by the producer during the study added significant N inputs to one set of buffers, and they were unable to assimilate sufficient N from both these inputs and the wastewater to protect shallow groundwater quality. In contrast, almost all samplings of shallow groundwater under the buffers receiving N only from the overland flow applied swine lagoon effluent showed nitrate (NO3-N) concentrations 20 and 30 m downslope to be lower than 10 mg L-1 (drinking water standard). On these buffers, NO3-N concentrations in shallow groundwater were near background levels five years after wastewater application commenced. The study indicated that the ratio of buffer area width to wastewater application area width on the landscape should be at least 1:1, and that buffers for protection of water quality should be continuous on the landscape. It was concluded from the study that buffers can be used at the farm scale to assimilate N from applied wastewater when they are sufficiently wide relative to waste application area, rate, and other N sources at the farm scale.