Manure Storage Facilities Research Articles

Auditing and Assessing Nutrient Management for Water Quality on Animal Feeding Operations

Concentrated animal feeding operations (AFO) and many AFO are required to comply with state and federal environmental regulations specifically related to the protection of water quality. Most regulations are based on the need to account for and control nutrient flow on-farm to minimize buildup, leaching, and runoff of nutrients that may pose a risk to surface and ground water quality. Attempts to encourage the control of nutrient flow include the requirements for comprehensive nutrient management plans (CNMP), conservation practice plans, storm water pollution prevention plans, animal mortality management, and emergency action plans. The overall goal of the CNMP on a livestock and poultry farm is to sustain a whole farm nutrient mass balance. An extensive auditing and assessment program evaluates the status of nutrient management on-farm and develops an action plan to minimize water pollution. An annual audit and review checks the performance of the concentrated AFO and AFO on environmental stewardship and identifies areas needing improvement. Critical control points that need to be audited and assessed are 1) nutrients imported on-farm, 2) nutrients exported off-farm, 3) nutrient status of soils and water, 4) manure handling and storage facilities, 5) conservation practices, 6) runoff waste water control, 7) land application practices, 8) animal mortality practices, 9) record keeping system, 10) operation and maintenance plan, and 11) alternative treatment systems, if applicable. Professional animal scientists can contribute significantly to livestock and poultry producers by providing assessments and audits of nutrient management along with other qualified professionals in the development of CNMP.

Computational Fluid Dynamics Modeling of Ventilation of Confined-Space Manure Storage Facilities: Applications

Fatalities associated with entry into on-farm confined-space manure storage tanks occur each year The fatalities are due to asphyxiation or poisoning by exposure to high concentrations of hydrogen sulfide, methane, and carbon dioxide. Forced ventilation has been shown to be an effective way to reduce concentrations of these noxious gases to levels that are safe for human entry into these storage tanks. Hydrogen sulfide (H2S) was used as an indicator gas to investigate the effectiveness of forced ventilation strategies for eliminating the toxic and oxygen-deficient atmospheres in confined-space manure tanks. Validated computational fluid dynamics (CFD) modeling protocols were used to simulate H2S evacuation from fan-ventilated manure tanks. The simulation studies were conducted for rectangular and circular manure tanks, and the effects of pollutant source, inter-contamination (process by which a portion of exhausted contaminant gas enters a ventilated confined airspace through the fresh air intake), storage size (i.e., length, diameter), and air exchange rate on H2S removalfrom fan-ventilated manure tanks were investigated. For the same air exchange rate, as the size (i.e., length, diameter) of the tank increased, the rate of evacuation of the H2S from the confined space decreased. For rectangular and circular manure tanks, the higher the air exchange rate, the higher the rate of evacuation of the H2S from the confined space. For the rectangular tank geometries and ventilation system layouts simulated, evacuation times decreased exponentially with air exchange rate. Evacuation times for the circular tanks simulated decreased linearly with air exchange rate.

Computational Fluid Dynamics Simulations of Gas Evacuation and O2 Recovery Times for Fan-Ventilated Confined-Space Manure Pits

Fatalities associated with entry into on-farm confined-space manure storage facilities occur each year. The fatalities are due to asphyxiation or poisoning by exposure to high concentrations of hydrogen sulfide, methane, carbon dioxide, or oxygen deficiency. Forced ventilation has been identified previously as an effective way to reduce concentrations of these noxious gases to levels that are safe for human entry into these facilities. Previously validated computational fluid dynamics (CFD) modeling protocols were used to identify the influence of several key initial conditions and modeling techniques on gas evacuation or oxygen recovery times for fan-ventilated confined-space manure pits. This article includes an extensive literature review to define the maximum expected initial concentrations and emission rates of primary manure gases in manure pits. The effect of the initial condition, the maximum initial concentrations of contaminant gases, on simulated contaminant gas evacuation time is explored. The influence of boundary conditions (i.e., emission rate (ER) and inter-contamination (INC), the process by which a portion of exhausted contaminant gas re-enters a ventilated confined airspace through the fresh air intake) on CFD outcomes is also explored. Simulation results showed that evacuation times increased as INC-strength (the ratio of contaminant concentration at the fan intake to the concentration in the air exhausted from the manure pit) increased from 0 to 0.40; however, no further increase in evacuation times was predicted for INC-strengths above 0.40. Simulations on oxygen recovery (from 0% to 20.0% by volume) in the confined airspace initially filled completely with a contaminant gas (i.e., H2S, NH3, CH4, and CO2) showed little difference (<5%) in recovery time by gas. Additionally, for a confined airspace (domain) filled with a gas mixture of contaminant gases, simulations showed that time to reduce H2S concentration from a documented high level (10,000 ppm) to the OSHA PEL level (10 ppm) was equal to or greater than evacuation times for other gases from their documented highest initial levels to their safe exposure levels. Also, an initial gaseous mixture including H2S and CO2 at their highest documented concentrations was the critical initial atmosphere in manure pits for performing CFD simulations.

Screening Ventilation Strategies for Confined-Space Manure Storage Facilities

Fatalities associated with entry into on-farm confined-space manure storage facilities occur each year. The fatalities are due to asphyxiation or poisoning by exposure to high concentrations of hydrogen sulfide, methane, and carbon dioxide. Forced ventilation has been shown to be an effective way to reduce concentrations of noxious gases to levels that are safe for human entry into these storage facilities. Hydrogen sulfide (H2S) was used as an indicator gas to investigate the effectiveness of forced-air ventilation strategies for eliminating the toxic and oxygen-deficient atmosphere in confined-space manure storage facilities. This article focuses on experimental methods for identifying ventilation strategies that effectively reduce toxic gas (i.e., H2S) concentrations in a fan-ventilated confined-space manure tank to the OSHA permissible exposure limit (PEL) (H2S PEL = 10 ppm) and to 25% of the initial gas concentration. Typical H2S concentration reduction curves during forced-air ventilation were identified in the tank as well. Based on the experimental tests conducted in this research, the most promising candidate ventilation strategies were identified for this rectangular confined-space manure tank with solid, fully slotted, and partially slotted covers. In addition, based on the results of experimental tests, a field-based database was developed for future validation of computational fluid dynamics modeling protocols.

Sulphate and sulphide corrosion in livestock buildings, Part I: Concrete deterioration

The liquid manure storage facilities of a swine or dairy operation constitute a significant part of the agricultural building infrastructure investment. It is important that these facilities perform as expected and that they do so for the expected life of the operation. However, concrete in farm buildings is subjected to severe hydrogen sulphide (H 2 S) and sulphate concentrations that result in the deterioration of reinforced concrete. This leads to premature deterioration of piers and floors, especially slatted floors. In some swine barns in Ontario a 50% loss of expected service life was reported when typical Portland cement concrete mixes were used. The results of this research will help find the most cost-effective solution for reducing concrete deterioration to a minimum and enhance the service life of reinforced concrete in livestock buildings, thus making better recommendations for durable structures in contact with manure. In the present study 48 concrete cylindrical specimens, 100 mm in diameter and 100 mm in height, with a reinforcing steel bar in the centre were exposed to H 2 S gas and sulphate solution, some for more than 3 years. One half of the specimens was partially immersed in sodium sulphate (20,000 ppm SO 4 2− ) and also subjected to H 2 S gas (1,000 ppm H 2 S). The second set was subjected to H 2 S gas only. Each set consisted of 8 different treatments including Portland cement (PC) concrete with 0.4 and 0.5 W/CM ratios, PC concrete with 8% silica fume replacement, 25% fly ash and 35% slag of the total amount of cementing material and specimens made of PC concrete with combinations of silica fume and fly ash (6%, 25%), and silica fume and slag (6%, 25%). Finally one treatment was carried out with sulphate-resistant cement. From the results it can be concluded that high-quality concrete with a low W/CM ratio and sulphate-resistant binder-like type 50 Portland cement (SR) is a simple and cost-effective method to produce durable reinforced concrete for livestock buildings. The sodium sulphate and H 2 S form a more corrosive environment than the H 2 S gas only.

Production of Levan by Bacillus licheniformis for Use as a Soil Sealant in Earthen Manure Storage Structures

Manure application is not permitted on frozen land in Canada and therefore, manure management and storage are the primary issues facing the agri-food industry. Low-cost, effective and environmentally safe earthen manure storage (EMS) facilities will lower costs and help make the livestock industry more competitive and efficient. The goal of this study was to develop a biological sealing technology for earthen manure storages. The results showed that it is feasible to use a growing culture of Bacillus licheniformis to produce a non viscous water insoluble levan. Levan can only be produced by Bacillus licheniformis during the growth mode. No levan was produced during the death phase. About 0.36 g of levan was produced per gram of sucrose which is 91.1% of theoretical yield. The polymer can be used as a plugging agent to plug the pores of high permeability soils. From the biological and biochemical characteristics of the Bacillus licheniformis, it appears that the organism is capable of producing levan from sucrose under most field and soil conditions. As a soil organism, Bacillus licheniformis should be able to compete with most common soil species such as Arthrobacter and Bacillus. The bacteria could be grown either in the non-polysaccharide producing mode or in the polysaccharide producing mode. The first would permit distribution of the bacteria to the lower soil layers but would delay the production of the polysaccharide due to the lag period required to produce the enzyme (levansucrase). Upon production of levan, pore spaces would close and hence, the hydraulic conductivity would be substantially reduced.

Mitigation of methane emissions during manure storage

Different materials for covering liquid manure storage facilities to reduce gaseous emissions were investigated on 65 l laboratory scale: perlite (Pegülit™), lightweight expanded clay aggregate (Leca™) and chopped straw – both individually and combined with lactic acid or saccharose, respectively. Methane is the predominant greenhouse gas emitted from liquid manure storage facilities. Common cover materials aim at the reduction of odour and ammonia emissions. But using them can increase greenhouse gas emissions. Especially straw can increase methane emissions. Lowering the pH of the slurry can reduce methane emissions. Covering and acidification were only effective in reducing methane emissions, when the pH was reduced below 6.0.

Greenhouse gas mitigation by covers on livestock slurry tanks and lagoons?

Liquid manure (slurry) storage facilities are important point sources of atmospheric pollution. Being point sources, containment of gaseous emissions via improved storage conditions may be possible, and permeable surface covers (natural crusts and artificial covers) are increasingly recognized for their capacity to reduce various gaseous emissions. Microbial transformations in permeable surface covers include bacterial methane oxidation, but this interface between nitrogen-rich slurry and the atmosphere is also an environment with intense nitrogen turnover than can lead to nitrous oxide emissions. Both methane and nitrous oxide are greenhouse gases, and strategies to reduce environmental impact of slurry stores must consider the total greenhouse gas balance. In this paper, greenhouse gas mitigation options for manure storages are discussed with reference mainly to practical storage conditions in Europe and North America.

Measuring greenhouse gas emissions from point sources in agriculture

Carbon dioxide, methane and nitrous oxide emissions from agricultural sources have a significant role in the overall enhancement of the global greenhouse gas (GHG) effect. In research, measurements of GHG emissions are made to improve upon emission factors used in national inventories, identify and promote mitigation practices, and drive policy on GHG emissions in agriculture. These measurements are fundamental to the process of better management of GHG emissions. There is a variety of measurement techniques used in GHG research depending on the measurement environment and available resources. Techniques that use chambers or micrometeorological measurements are commonly employed for calculating emissions of GHG from point sources in agriculture, such as livestock and manure-holding facilities. This review examines these techniques, their limitations, and discusses methods to quantify their accuracy and precision. Emerging techniques like the use of dispersion models provide opportunities to directly determine emissions from whole farms. A few micrometeorological techniques (integrated horizontal flux and mass difference) are ideal for point sources such as manure storage facilities. For smaller sources, chambers are still recommended. In designing GHG emission studies, employing more than one technique when measuring GHG emissions is recommended, as often differences can exist due to technique. Ideally, a controlled release of the target gas, and its recovery, should also be conducted to evaluate techniques prior to their application. Although many techniques are often sensitive enough to quantify mitigation practices, i.e., the relative change in emissions, it is more difficult to determine “ true”emission factors as required for inventory work. It follows that the precision and accuracy of the techniques must accompany their application when estimating GHG emissions. Key words: Greenhouse gas, techniques, chambers, methane, agriculture, cattle

Infectious Swine Hepatitis E Virus Is Present in Pig Manure Storage Facilities on United States Farms, but Evidence of Water Contamination Is Lacking

Fresh feces, manure slurry (from earthen lagoons and/or concrete pits), and drinking and surface water samples were collected from 28 pig farms in the Midwestern United States. All samples were tested for hepatitis E virus (HEV) RNA by reverse transcription-PCR. Seven of 28 farms had fecal samples that contained HEV. Of 22 farms where pit samples were accessible, 15 contained HEV, and of 8 farms that had lagoons, 3 contained HEV. The highest virus titers were 10 and 10(3) genome equivalents per 60 ml of manure slurry in lagoon and pit samples, respectively. None of the water samples tested HEV positive. To determine the infectivity of the HEV found in the positive farm 19 lagoon (designated L19) or farm 12 pit (designated P12) samples, pigs were inoculated either intravenously (n = 3) or orally (n = 3) with the L19 or P12 manure slurry. Four pigs inoculated intravenously with prototype swine HEV served as positive controls. All positive-control pigs shed HEV in feces and 3 of 4 developed anti-HEV antibodies. Two pigs in the intravenously inoculated P12 group shed HEV in feces, and one of the pigs seroconverted to anti-HEV antibodies. None of the pigs in the negative-control, L19 oral, L19 intravenous, or P12 oral group shed HEV in feces. The findings indicate that HEV found in pig manure slurry was infectious when inoculated intravenously. Pit manure slurry is a potential source of HEV infection and for contamination of the environment. Contamination of drinking or surface water with HEV was not found on or near the pig farms.

Greenhouse gas emissions from covered slurry compared with uncovered during storage

Abstract Liquid manure storage facilities are sources of methane, nitrous oxide and ammonia emissions. Different materials for covering liquid manure storage facilities to reduce gaseous emissions were investigated on laboratory scale (65 l): perlite (Pegulit™), lightweight expanded clay aggregate (Leca™) and chopped straw—both individually and combined with lactic acid or saccharose, respectively. Methane is the predominant greenhouse gas emitted from liquid manure storage facilities. Nitrous oxide plays a role when surfaces become encrusted when it occurs by using the cover materials investigated. Common cover materials have good reduction effects on ammonia but less on greenhouse gas emissions. Straw can increase emissions of methane and nitrous oxide, as can granules. Lowering the pH value of the slurry can reduce both methane and nitrous oxide emissions. Combinations of covering and acidifying should cause a pH value below 6.0 to reduce methane and nitrous oxide emissions effectively. Lower pH value seems to be necessary also to reduce ammonia emissions effectively.

Prediction of Manure and Nutrient Excretion from Dairy Cattle

Accurate estimates of manure excretion are needed for planning manure storage facilities and for nutrient management. Data sets from metabolism studies conducted at several universities were compiled and evaluated for excretion of total manure, N, P, and K. Animal groups included calves weighing up to 204kg, heifers weighing between 274 and 613kg, nonlactating cows, and lactating cows. Regression equations were developed to predict excretion of total manure, total dry matter, N, P, and K. Predictors used in the regression equations for lactating cows included milk yield, percentages of protein and fat in milk, dietary concentrations of crude protein and neutral detergent fiber, and intakes of nutrients. The regression equations provide improved predictions of excretion and enable more accurate planning of manure storage and nutrients to be managed at the farm level.

GREENHOUSE GAS EMISSIONS FROM LIQUID SWINE MANURE STORAGE FACILITIES IN SASKATCHEWAN

Greenhouse gas (GHG) emissions from manure storage facilities at four different commercial farrow-to-finishswine operations under liquid manure management located in Saskatchewan, Canada, were experimentally determinedduring the spring-to-fall period between 2001 and 2003. These operations featured three types of manure storage facilities:uncovered concrete tank, uncovered earthen manure basin (EMB), and covered (blown chopped straw) EMB. GHG emissionrates were expressed in terms of unit mass of animal producing the stored manure. On average, methane and carbon dioxideemission rates were respectively 3.75 g CO2 equivalent day-1 kg-1 and 1.73 g CO2 equivalent day-1 kg-1, while nitrous oxideemission rates were negligible. The total average GHG emission rate measured in this study was 5.48 g CO2 equivalent day-1kg-1. On average, GHG emissions from the uncovered EMB were the largest, while those from the covered EMB were thelowest. Emissions were maximum during the summer and at their lowest during the spring, and night emissions were largerthan those that occurred during the daytime. Estimations based on the results of this study indicate that the addition of a blownchopped straw cover on an EMB can yield reductions in CO2 and CH4 emissions of 56 and 786 tonnes of CO2 equivalent peryear, respectively, for each 1,000-sow increment.

Lagoon-biogas emissions and carbon balance estimates of a swine production facility.

Gaseous emissions from animal manure storage facilities can contribute to global greenhouse gas inventories. Biogas fluxes were measured for one year from a 2-ha anaerobic lagoon that received waste from a 10500-head swine (Sus scrofa) finishing operation in southwestern Kansas. During 2001, ebullition of biogas was measured continuously by using floating platforms equipped with gas-collection domes. Periodically, the composition of the biogas was determined by using gas chromatography. Detailed records of feed quality and quantity and animal weights and gains also were obtained to determine the carbon budget of the facility (barns and lagoon). Flux of biogas was very seasonal, with peak emission (18.7 mol m(-2) d(-1)) occurring in early June. Nearly 50% of the annual biogas losses occurred during a 30-d period beginning on day of year (DOY) 146. Flux patterns suggest that the start of the high biogas production period was governed by temperature, while the decline in production in mid-June was caused by substrate limitations. Average biogas composition was 0.71 L CH4 L(-1). The quantity of CH4 released from the lagoon was 86.3 Mg yr(-1), which represents about 38 g of CH4 per kg of animal weight gain. The average flux density of biogas from the lagoon was 382 mol m(-2) yr(-1) or 728 mol yr(-1) per resident animal where the resident animal population was 10500. Flux rates of CH4 were 1.7 to 3.4 times less than predictions made with Intergovernmental Panel on Climate Change (IPCC) models. Additional research is needed on the carbon budgets of other animal feeding operations so that better estimates of greenhouse gas emissions can be determined.

Impact of agricultural practices and river catchment characteristics on river and bathing water quality

The objective was to investigate the potential risk of faecal indicator organism (FIO) bacteriological contamination of river catchments and coastal bathing waters from farm management practices and to develop practices to reduce the risk. A risk assessment on 117 farms was carried out in two river catchments in south-west Scotland. Manure storage facilities, farming practices, field conditions and catchment characteristics were assessed. River samples at 33 locations were regularly taken and analysed for FIOs. Available manure storage capacity and farm management practices are inadequate on a high proportion of farms and FIO contamination of watercourses was likely the result of effluent transported into watercourses due to non-collection or poor containment. In addition, surface run-off or leaching following land application of manure or intensive stocking in adverse conditions was a high risk on up to 50% of farms. The concentrations of FIOs in the streams of two sub-catchments with high livestock intensity was 4 to 8 times higher compared to the two sub-catchments which had a low livestock intensity. The majority of potential risks of agricultural pollution to watercourses may be eliminated through improved manure and dirty water management, forward planning of manure spreading activities and improved operational procedures.

Optimization of Phosphorus Index and Costs of Manure Management on a New York Dairy Farm

Manure allocation on large‐scale confinement animal feeding operations is a complex management decision. This study assesses the cost effectiveness and the risk of P loss associated with various combinations of manure management options for a typical midsized dairy farm in New York State. The farm has 587 adult dairy cows (Bos taurus) and 430 young animals (1202 animal units). Fifty‐three fields (26 cornfields and 27 pastures) ranging in size from 1 to 15 ha are available to receive livestock manure. Morgan's Soil Test P values range from 1.1 to 87.3 kg ha−1 (mean of 20.1 kg ha−1). Options included optimal allocation of manure in time and space, surface application, incorporation, and manure storage facilities of three‐, six‐, and eight‐month storage capacities. The decision process considered nutrient management costs (manure handling and fertilization) and the New York State P Site Index (P Index) as an indicator of one of the environmental impacts of manure management. Mathematical programming techniques and utility functions are used to select the best combination of manure management practices. The results show a convergence indicating that the best management decision would be to follow a manure allocation scheme optimized in time and space, to have three months of manure storage capacity, and to surface‐apply manure. Compared with current practices, the recommended combination of practices results in an approximate 45% reduction in the mean area‐weighted P Index (64.2 vs. 36.1) for a cost increase of less than 2% ($146 573 vs. $148 821).

Hydrogen sulfide assessment in shallow-pit swine housing and outside manure storage.

In Saskatchewan, some recent incidents have lead us to believe that certain manure management activities can potentially release high concentrations of H2S into the atmosphere of shallow-pit barns. The objectives of the monitoring project reported here were to evaluate worker exposure to H2S during the completion of the following tasks: emptying of in-barn shallow manure pits, power washing of barn rooms, and agitation and emptying of outdoor manure storage facilities. In-barn monitoring was performed in gestation, farrowing, nursery, and grow-finish sections in the summer of 2001 and the winter of 2002 on four different farms. Plug pulling can generate very high concentrations of H2S. The maximum values recorded during some of the monitored events reached 1,000 ppm. The H2S released as a plug is being pulled does not follow a predictable pattern when considering the level that will be reached, the concentration variations during the event, and the time at which the peak concentration will be observed. Power washing generated lower H2S concentrations than plug pulling. However, as the task to be performed generally takes time, the 15 min time-weighed average of 15 ppm (STEL) can be reached after the task started and can be exceeded for a long period of time, which for some of the monitored events was more than 30 min. Finally, monitoring at the storage facilities showed that the risks of exposure to excessive H2S concentrations during the agitation and emptying of outside manure storage facilities were very limited. Results from this study suggest that pig production buildings involving short-term storage of liquid manure may present H2S exposure risks that have been underestimated until now. All workers should be provided with an H2S monitor and safety equipment to ensure that workers are protected when the H2S concentration rises. As well, engineering controls have to be developed to prevent H2S formation in the manure or H2S emission into the worker/pig space.

Optimization of Phosphorus Index and Costs of Manure Management on a New York Dairy Farm

Manure allocation on large-scale confinement animal feeding operations is a complex management decision. This study assesses the cost effectiveness and the risk of P loss associated with various combinations of manure management options for a typical midsized dairy farm in New York State. The farm has 587 adult dairy cows (Bos taurus) and 430 young animals (1202 animal units). Fifty-three fields (26 cornfields and 27 pastures) ranging in size from 1 to 15 ha are available to receive livestock manure. Morgan's Soil Test P values range from 1.1 to 87.3 kg ha−1 (mean of 20.1 kg ha−1). Options included optimal allocation of manure in time and space, surface application, incorporation, and manure storage facilities of three-, six-, and eight-month storage capacities. The decision process considered nutrient management costs (manure handling and fertilization) and the New York State P Site Index (P Index) as an indicator of one of the environmental impacts of manure management. Mathematical programming techniques and utility functions are used to select the best combination of manure management practices. The results show a convergence indicating that the best management decision would be to follow a manure allocation scheme optimized in time and space, to have three months of manure storage capacity, and to surface-apply manure. Compared with current practices, the recommended combination of practices results in an approximate 45% reduction in the mean area-weighted P Index (64.2 vs. 36.1) for a cost increase of less than 2% ($146 573 vs. $148 821).

Rapid Analysis of Hog Manure and Manure‐amended Soils Using Near‐infrared Spectroscopy

Application of hog (Sus domesticus) manure to agricultural land converts waste to fertilizer. Nevertheless, matching nutrients in highly variable manure to soil or crop needs requires analytical capability that is ideally field portable and cost‐effective. This study explored using rapid nondestructive near‐infrared spectroscopy (NIRS) to analyze nutrients in hog manure and receiving soil. Spectral data in the visible and near‐infrared (NIR) region (400–2500 nm) from manure samples were correlated with chemical analytical data from the same samples using multiple linear regression statistics to develop calibrations for the prediction of future unknown samples. For 64 manure samples from seven manure storage facilities, r2 between NIR‐predicted values and chemically measured values was 0.93 to 0.99 for NH4–N, total dissolved N (TDN), suspended N, soluble reactive P (SRP), total dissolved P (TDP), suspended P, suspended C, Na, and Mg. For K, Ca, conductivity, and pH, r2 was &gt;0.80. Subsequent analysis of 75 samples from 25 facilities gave similar or slightly less successful results. Soil samples collected before and following application of manure were scanned in a field‐moist state and after drying. For field‐moist soil, r2 for N, organic matter, Mg, and moisture was &gt;0.84; for SO4–S was 0.7. For dry soil, results were similar for N and better for Mg SO4–S, Ca, and K. Near‐infrared spectroscopy has potential to predict some nutrient and salt concentrations in manure rapidly and without sample preparation. It can determine moisture, organic matter, total N, and Mg in field‐moist or dry soil and SO4–S, Ca, and possibly K in dry soil.

A LONG‐TERM, WATERSHED‐SCALE, EVALUATION OF THE IMPACTS OF ANIMAL WASTE BMPs ON INDICATOR BACTERIA CONCENTRATIONS1

ABSTRACT: Driven by increasing concerns about bacterial pollution from agricultural sources, states such as Virginia have initiated cost sharing programs that encourage the use of animal waste best management practices (BMPs) to control this pollution. Although a few studies have shown that waste management BMPs are effective at the field scale, their effectiveness at the watershed scale and over the long term is unknown. The focus of this research was to evaluate the effectiveness of BMPs in reducing bacterial pollution at the watershed scale and over the long term. To accomplish this goal, a 1,163 ha watershed located in the Piedmont region of Virginia was monitored over a ten‐year period. Fecal coliforms (FC) and fecal streptococci (FS) were measured as indicators of bacterial pollution. A pre‐BMP versus post‐BMP design was adopted. Major BMPs implemented were manure storage facilities, stream fencing, water troughs, and nutrient management. Seasonal Kendall trend analysis revealed a significant decreasing trend during the post‐BMP period for FC concentrations at the watershed outlet, but not at the subwatershed level. Implementation of BMPs also resulted in a significant reduction in the geometric mean of FS concentrations. FC concentrations in streamflow at the watershed outlet exceeded the Virginia primary standard 86 and 74 percent of the time during pre‐BMP and post‐BMP periods, respectively. Corresponding exceedances for the secondary standard were 50 and 41 percent. Violations decreased only slightly during the post‐BMP period. The findings of this study suggest that although BMP implementation can be expected to accomplish some improvement in water quality, BMP implementation alone may not ensure compliance with current water quality standards.