Environmental and economic comparisons of manure application methods in farming systems

Alternative methods for applying livestock manure to no-till soils involve environmental and economic trade-offs. A process-level farm simulation model (Integrated Farm System Model) was used to evaluate methods for applying liquid dairy (Bos taurus L.) and swine (Sus scrofa L.) manure, including no application, broadcast spreading with and without incorporation by tillage, band application with soil aeration, and shallow disk injection. The model predicted ammonia emissions, nitrate leaching, and phosphorus (P) runoff losses similar to those measured over 4 yr of field trials. Each application method was simulated over 25 yr of weather on three Pennsylvania farms. On a swine and cow-calf beef operation under grass production, shallow disk injection increased profit by $340 yr(-1) while reducing ammonia nitrogen and soluble P losses by 48 and 70%, respectively. On a corn (Zea mays L.)-and-grass-based grazing dairy farm, shallow disk injection reduced ammonia loss by 21% and soluble P loss by 76% with little impact on farm profit. Incorporation by tillage and band application with aeration provided less environmental benefit with a net decrease in farm profit. On a large corn-and-alfalfa (Medicago sativa L.)-based dairy farm where manure nutrients were available in excess of crop needs, incorporation methods were not economically beneficial, but they provided environmental benefits with relatively low annual net costs ($13 to $18 cow). In all farming systems, shallow disk injection provided the greatest environmental benefit at the least cost or greatest profit for the producer. With these results, producers are better informed when selecting manure application equipment.     

An operational method for the evaluation of resource use and environmental impacts of dairy farms by life cycle assessment

This paper describes and applies EDEN-E, an operational method for the environmental evaluation of dairy farms based on the life cycle assessment (LCA) conceptual framework. EDEN-E requires a modest amount of data readily available on-farm, and thus can be used to assess a large number of farms at a reasonable cost. EDEN-E estimates farm resource use and pollutant emissions mostly at the farm scale, based on-farm-gate balances, amongst others. Resource use and emissions are interpreted in terms of potential impacts: eutrophication, acidification, climate change, terrestrial toxicity, non-renewable energy use and land occupation. The method distinguishes for each total impact a direct component (impacts on the farm site) and an indirect component (impacts associated with production and supply of inputs used). A group of 47 dairy farms (41 conventional and six organic) was evaluated. Expressed per 1000 kg of fat-and-protein-corrected milk, total land occupation was significantly larger for organic than for conventional farms, while total impacts for eutrophication, acidification, climate change, terrestrial toxicity, and non-renewable energy use were not significantly different for the two production modes. When expressed per ha of land occupied all total impacts were significantly larger for conventional than organic farms. This study largely confirms previously published findings concerning the effect of production mode on impacts of dairy farms. However, it strikingly reveals that, for the set of farms examined, the contribution of production mode to overall inter-farm variability of impacts was minor relative to inter-farm variability within each of the two production modes examined. The mapping of impact variability through EDEN-E opens promising perspectives to move towards sustainable farming systems by identifying the structural and management characteristics of the farms presenting the lowest impacts.     

A Sensitivity Analysis of Nitrogen Losses from Dairy Farms

International attention has focused on agricultural production systems as non-point sources of pollution affecting the quality of streams, estuaries and ground water resources. The objective of the current study was to develop a model of nitrogen management on the dairy farm, and to perform sensitivity analyses in order to determine the relative importance of manipulating herd nutrition, manure management and crop selection in reducing nitrogen (N) losses from the farm. The importance of the method of N input to the farm (purchased feed, legume fixation, inorganic fertilizer, imported manure) was investigated, and the potential to reduce N losses from dairy farms was evaluated. Nitrogen balance equations were derived, and related efficiency coefficients were set to reference values representing common management practices. Total farm N efficiency (animal product N per N input), and N losses per product N were determined for different situations by solving the set of simultaneous equations. Improvements in animal diet and management that increase the conversion of feed N to animal product by 50% would increase total farm N efficiency by 48% and reduce N losses per product by 36 to 40%. In contrast, reducing losses from manure collection, storage and application to improve the percentage of manure N that becomes available in soil by 100% would only improve total farm N efficiency by 13% and reduce total N losses by 14%. Selecting crops and management that can use soil nutrients 50% more efficiently would improve total farm efficiency by up to 59% and reduce N losses by up to 41% depending on the predominant nitrogen sources to the farm. Legume production would reduce N losses per product compared with non-legumes. There was more than a five fold difference in N losses per animal product N between the most extreme scenarios suggesting considerable opportunity to reduce N losses from dairy farms.     

Reducing phosphorus runoff from dairy farms

Phosphorus (P) runoff from manure can lead to eutrophication of surface water and algae growth. This study evaluates the impacts of alternative P reduction practices on dairy farm net returns and on potential P runoff. The P control practices include dairy herd nutrient management, crop nutrient management, and runoff and erosion control. Four farms representative of dairies in the Virginia Shenandoah Valley are simulated including dairies with and without supplementary broiler enterprises and with average and below average land area. A mathematical programming model was developed to predict farm production and net returns and the GLEAMS model was used to predict potential P runoff. The farms are evaluated under four scenarios: Scenario 1, no constraint on P runoff with access to crop nutrient, runoff and erosion control strategies but no access to dairy herd nutrient control strategies; Scenario 2, no constraint on P runoff with access to all crop and dairy herd nutrient control strategies; Scenario 3, constraint on P runoff with access to crop nutrient, runoff and erosion control strategies but no access to dairy herd nutrient control strategies; and Scenario 4, constraint on P runoff with access to all crop and dairy herd nutrient control strategies. Under Scenario 2, the herd nutrient control strategies increase milk output per cow and net returns on both farms and reduce P content of manure and P runoff. Under Scenario 3, limiting P runoff reduces farm returns by 1 and 3% on the average and small farms, respectively. Under Scenario 4, the P runoff constraint is less costly, reducing returns by less than 1% on both farms. Animal nutrient control strategies should be an important part of pollution control policies and programs for livestock intensive watersheds.     

Implementing Innovative Drainage Management Practices in the Mississippi River Basin to Enhance Nutrient Reductions

In the Mississippi River Basin (MRB), practices that enhance drainage (e.g., channelization, tile drainage) are necessary management tools in order to maintain optimal agricultural production in modern farming systems. However, these practices facilitate, and may speed the delivery of excess nutrients and sediments to downstream water bodies via agricultural streams and ditches. These nonpoint sources contribute to elevated nutrient loading in the Gulf of Mexico, which has been linked to widespread hypoxia and associated ecological and economic problems. Research suggests agricultural drainage ditches are important links between farm fields and downstream ecosystems, and application of new management practices may play an important role in the mitigation of water quality impairments from agricultural watersheds. In this article, we describe how researchers and producers in the MRB are implementing and validating novel best management practices (BMPs) that if used in tandem could provide producers with continued cropping success combined with improved environmental protection. We discuss three BMPs — low‐grade weirs, slotted inlet pipes, and the two‐stage ditch. While these new BMPs have improved the quality of water leaving agricultural landscapes, they have been validated solely in isolation, at opposite ends of the MRB. These BMPs have similar function and would greatly benefit from stacked incorporation across the MRB to the benefit of the basin as a whole.     

Multivariate analysis of paired watershed data to evaluate agricultural best management practice effects on stream water phosphorus

Quantification of the effects of management programs on water quality is critical to agencies responsible for water resource protection. This research documents reductions in stream water phosphorus (P) loads resulting from agricultural best management practices (BMPs) implemented as part of an effort to control eutrophication of Cannonsville Reservoir, a drinking water supply for New York City. Dairy farms in the upstate New York reservoir basin were the target of BMPs designed to reduce P losses. A paired watershed study was established on one of these farms in 1993 to evaluate changes in P loading attributable to implementation of BMPs that included manure management, rotational grazing, and improved infrastructure. Intensive stream water monitoring provided data to calculate P loads from the 160-ha farm watershed for all runoff events during a two-year pre-treatment period and a four-year post-treatment period. Statistical control for inter-annual climatic variability was provided by matched P loads from a nearby 86-ha forested watershed, and by several event flow variables measured at the farm. A sophisticated multivariate analysis of covariance (ANCOVA) provided estimates of both seasonal and overall load reductions. Statistical power and the minimum detectable treatment effect (MDTE) were also calculated. The results demonstrated overall event load reductions of 43% for total dissolved phosphorus (TDP) and 29% for particulate phosphorus (PP). Changes in farm management practices and physical infrastructure clearly produced decreases in event P losses measurable at the small watershed scale.     

Multiscale effects of management, environmental conditions, and land use on nitrate leaching in dairy farms

Nitrate leaching in intensive grassland- and silage maize-based dairy farming systems on sandy soil is a main environmental concern. Here, statistical relationships are presented between management practices and environmental conditions and nitrate concentration in shallow groundwater (0.8 m depth) at farm, field, and point scales in The Netherlands, based on data collected in a participatory approach over a 7-yr period at one experimental and eight pilot commercial dairy farms on sandy soil. Farm milk production ranged from 10 to 24 Mg ha(-1). Soil and hydrological characteristics were derived from surveys and weather conditions from meteorological stations. Statistical analyses were performed with multiple regression models. Mean nitrate concentration at farm scale decreased from 79 mg L(-1) in 1999 to 63 in 2006, with average nitrate concentration in groundwater decreasing under grassland but increasing under maize land over the monitoring period. The effects of management practices on nitrate concentration varied with spatial scale. At farm scale, nitrogen surplus, grazing intensity, and the relative areas of grassland and maize land significantly contributed to explaining the variance in nitrate concentration in groundwater. Mean nitrate concentration was negatively correlated to the concentration of dissolved organic carbon in the shallow groundwater. At field scale, management practices and soil, hydrological, and climatic conditions significantly contributed to explaining the variance in nitrate concentration in groundwater under grassland and maize land. We conclude that, on these intensive dairy farms, additional measures are needed to comply with the European Union water quality standard in groundwater of 50 mg nitrate L(-1). The most promising measures are omitting fertilization of catch crops and reducing fertilization levels of first-year maize in the rotation.     

Farm factors associated with reducing Cryptosporidium loading in storm runoff from dairies

A systems approach was used to evaluate environmental loading of Cryptosporidium oocysts on five coastal dairies in California. One aspect of the study was to determine Cryptosporidium oocyst concentrations and loads for 350 storm runoff samples from dairy high use areas collected over two storm seasons. Selected farm factors and beneficial management practices (BMPs) associated with reducing the Cryptosporidium load in storm runoff were assessed. Using immunomagnetic separation (IMS) with direct fluorescent antibody (DFA) analysis, Cryptosporidium oocysts were detected on four of the five farms and in 21% of storm runoff samples overall. Oocysts were detected in 59% of runoff samples collected near cattle less than 2 mo old, while 10% of runoff samples collected near cattle over 6 mo old were positive. Factors associated with environmental loading of Cryptosporidium oocysts included cattle age class, 24 h precipitation, and cumulative seasonal precipitation, but not percent slope, lot acreage, cattle stocking number, or cattle density. Vegetated buffer strips and straw mulch application significantly reduced the protozoal concentrations and loads in storm runoff, while cattle exclusion and removal of manure did not. The study findings suggest that BMPs such as vegetated buffer strips and straw mulch application, especially when placed near calf areas, will reduce environmental loading of fecal protozoa and improve stormwater quality. These findings are assisting working dairies in their efforts to improve farm and ecosystem health along the California coast.     

Economic analysis of best management practices to reduce watershed phosphorus losses

In phosphorus-limited freshwater systems, small increases in phosphorus (P) concentrations can lead to eutrophication. To reduce P inputs to these systems, various environmental and agricultural agencies provide producers with incentives to implement best management practices (BMPs). In this study, we examine both the water quality and economic consequences of systematically protecting saturated, runoff-generating areas from active agriculture with selected BMPs. We also examine the joint water quality/economic impacts of these BMPs-specifically BMPs focusing on barnyards and buffer areas. Using the Variable Source Loading Function model (a modified Generalized Watershed Loading Function model) and net present value analysis (NPV), the results indicate that converting runoff-prone agricultural land to buffers and installing barnyard BMPs are both highly effective in decreasing dissolved P loss from a single-farm watershed, but are also costly for the producer. On average, including barnyard BMPs decreases the nutrient loading by about 5.5% compared with only implementing buffers. The annualized NPV for installing both buffers on only the wettest areas of the landscape and implementing barnyard BMPs becomes positive only if the BMPs lifetime exceeds 15 yr. The spatial location of the BMPs in relation to runoff producing areas, the time frame over which the BMPs are implemented, and the marginal costs of increasing buffer size were found to be the most critical considerations for water quality and profitability. The framework presented here incorporates estimations of nutrient loading reductions in the economic analysis, and is applicable to farms facing BMP adoption decisions.     

Adoption of Stream Fencing Among Dairy Farmers in Four New Zealand Catchments

The effect of dairy farming on water quality in New Zealand streams has been identified as an important environmental issue. Stream fencing, to keep cattle out of streams, is seen as a way to improve water quality. Fencing ensures that cattle cannot defecate in the stream, prevents bank erosion, and protects the aquatic habitat. Stream fencing targets have been set by the dairy industry. In this paper the results of a study to identify the factors influencing dairy farmers' decisions to adopt stream fencing are outlined. Qualitative methods were used to gather data from 30 dairy farmers in four New Zealand catchments. Results suggest that farm contextual factors influenced farmers' decision making when considering stream fencing. Farmers were classified into four segments based on their reasons for investing in stream fencing. These reasons were fencing boundaries, fencing for stock control, fencing to protect animal health, and fencing because of pressure to conform to local government guidelines or industry codes of practice. This suggests that adoption may be slow in the absence of on-farm benefits, that promotion of stream fencing needs to be strongly linked to on-farm benefits, and that regulation could play a role in ensuring greater adoption of stream fencing.     

The relationship between milk production and farm-gate nitrogen surplus for the Waikato region, New Zealand

As the scope and scale of New Zealand (NZ) dairy farming increases, farmers and the industry are being challenged by Government and the New Zealand public to address growing environmental concerns. Dairying has come under increasing scrutiny from local authorities tasked with sustainable resource management. Despite recent efforts of farmers and industry to improve resource use efficiency, there is increasing likelihood of further regulatory constraints on water use and nutrient management. This study uses available data on farm-gate nitrogen (N) surpluses and milk production from the Waikato, New Zealand's largest dairying region, together with a farm scale modeling exercise, to provide a perspective on the current situation compared to dairy farms in Europe. It also aims to provide relevant guidelines for N surpluses and efficiencies under NZ conditions. Waikato dairy farms compare favorably with farms in Europe in terms of N use efficiency expressed as L milk/kg farm-gate N surplus. Achievable and realistic good practice objectives for Waikato dairy farmers could be 15,000 L milk/ha (1200 kg milk fat plus protein/ha) with a farm-gate N surplus of 100 kg/ha giving an eco-efficiency (L milk/kg N surplus) of 150, and long-term average nitrate leaching losses of approximately 25-30 kg/ha/yr. This can be achieved by increasing the N conversion efficiency through lower replacement rates (16 versus 22%), lower stocked (< 3 cows/ha) high genetic merit cows (30 L milk/day at peak) milked for longer (277 versus 240 days), feeding effluent-irrigated, home-grown, low-protein supplements to cows on high-protein, grass-clover pastures to dilute N concentration in the diet, removing some of the urinary N from the paddocks during critical times by standing cows on a loafing pad for part of the day, and through lower N fertilizer rates (50-70 kg/ha/yr compared to the norm of 170-200 kg/ha/yr) and using a nitrification inhibitor and gibberellins to boost pasture growth and the former to reduce N leaching.     

A whole-farm strategy to reduce environmental impacts of nitrogen

Dutch regulations for ammonia emission require farmers to inject slurry into the soil (shallow) or to apply it in narrow bands at the surface. For one commercial dairy farm in the Netherlands it was hypothesized that its alternative farming strategy, including low-protein feeding and surface spreading, could be an equally effective tool for ammonia emission abatement. The overall objective of the research was to investigate how management at this farm is related to nitrogen (N) losses to the environment, including groundwater and surface water. Gaseous emission of ammonia and greenhouse gasses from the naturally ventilated stables were 8.1 and 3.1 kg yr(-1) AU(-1) on average using the internal tracer (SF(6))-ratio method. Measurements on volatilization of ammonia from slurry application to the field using an integrated horizontal flux method and the micrometeorological mass balance method yielded relatively low values of ammonia emissions per ha (3.5-10.9 kg NH(3)-N ha(-1)). The mean nitrate concentration in the upper ground water was 6.7 mg L(-1) for 2004 and 3.0 mg L(-1) for 2005, and the half-year summer means of N in surface water were 2.3 mg N L(-1) and 3.4 mg N L(-1) for 2004 and 2005, respectively. Using a nutrient budget model for this farm, partly based on these findings, it was found that the calculated ammonia loss per ton milk (range 5.3-7.5 kg N Mg(-1)) is comparable with the estimated ammonia loss of a conventional farm that applies animal slurry using prescribed technologies.     

MANAGEMENT AND POLICY EFFECTS ON POTENTIAL GROUNDWATER CONTAMINATION FROM DAIRY WASTE1

ABSTRACT: A combined economic and water quality modeling framework was used to evaluate impacts of alternative policies and management practices on reducing nitrate movement to groundwater for dairy farms in Rockingham County, Virginia. The analysis considers three on-farm manure storage options, cost-sharing programs for purchasing manure storage facilities, restrictions on nitrogen application rates, and a tax on commercial fertilizer. The CREAMS model was used to estimate nitrate leaching from the crop root zone for various nutrient (and manure) management practices, based on timing and rate of manure and fertilizer applications. The mixed-integer programming economic model considers water quality, policy, and economic constraints in comparing the profitability of alternative cropping and nutrient management systems that reduce groundwater contamination potential. The study provides both the environmental and economic effects of better management of dairy waste.     

Flood Risk Reduction from Agricultural Best Management Practices

Best management practices (BMPs) play an important role in improving impaired water quality from conventional row crop agriculture. In addition to reducing nutrient and sediment loads, BMPs such as fertilizer management, reduced tillage, and cover crops could alter the hydrology of agricultural systems and reduce surface water runoff. While attention is devoted to the water quality benefits of BMPs, the potential co‐benefits of flood loss reduction are often overlooked. This study quantifies the effects of selected commonly applied BMPs on expected flood loss to agricultural and urban areas in four Iowa watersheds. The analysis combines a watershed hydrologic model, hydraulic model outputs, and a loss estimation model to determine relationships between hydrologic changes from BMP implementations and annual economic flood loss. The results indicate a modest reduction in peak discharge and economic loss, although loss reduction is substantial when urban centers or other high‐value assets are located downstream in the watershed. Among the BMPs, wetlands, and cover crops reduce losses the most. The research demonstrates that watershed‐scale implementation of agricultural BMPs could provide benefits of flood loss reduction in addition to water quality improvements.     

Nutrient-Balance Modeling as a Tool for Environmental Management in Aquaculture: The Case of Trout Farming in France

The control and prevention of nutrient pollution from fish farming plays an essential role in the French regulatory framework. Assessing nutrient emissions from fish farms is important in terms of farm authorization, taxation, and monitoring. Currently employed strategies involve both water sampling and empirical modeling. This article reports the work and outcomes of an expert panel that evaluated existing methodologies and their possible alternatives. The development and evaluation of a nutrient-balance approach was assessed as a potential alternative to currently used methodologies. A previously described nutrient-balance model was suggested and parameterized using expert choice, and its validity and applicability were assessed. The results stress that the nutrient-balance model provides more robust and relatively conservative waste estimates compared to the currently used methodologies. Sensitivity of the approach to the uneven data quality available at farm level, difficulties of on-farm measurements, as well as model requirements and limitations are discussed.     

From pioneering to organised business: the development of ecological farming in China

ABSTRACT

Small-scale ecological farming and their associated alternative food networks, are increasingly important in China, as a response to poor farm incomes and as a contribution to widespread concerns about environmental degradation and food safety. However, despite the enormous market potential and the notable success of some ventures, this type of farming remains at the margins, with many businesses struggling to develop beyond their start-up phase and consumers struggling to build confidence in the new produce and routes to market. Many of these farms display the classic elements of pioneer businesses, including high reliance on charismatic individuals, insecure land rights, high transaction and monitoring costs and fragile routes to market. Empirically, many of these businesses fail because they cannot grow out of the pioneer phase before the pioneer grows tired of the business. While this is a problem for all small businesses, it is particularly acute in business sectors like ecological farming in China, where there is little evidence of suitable and sustainable developmental models. Using Bernardus Lievegoed's work on organisational development applied to two case study farms, we suggest that there are Western developmental models that are applicable to small-scale ecological farming and that have the potential to offer insights into how this might be achieved with Chinese characteristics. We conclude by arguing that, Chinese ecological farms have to plan explicitly for a form of development that allows them to remain committed to their ideals while moving them away from dependence on charismatic people, family labour and volatile customer bases.     

Farm management indicators and farm typologies as a basis for assessments in a changing policy environment

This paper focuses on the assessment of farm management indicators and argues that typologies are a necessary tool for comprehensive environmental assessments. In the paper Andersen et al., [(2004a). Farming and the Environment in the European Community--using agricultural statistics to provide farm management indicators. Paper presented at OECD Expert meeting, March 2004, New Zealand. < http:webdomino1.oecd.org/comnet/agr/farmind.nsf/viewHtml/index/$FILE/Anderson_et_al.PDF> (1st of February 2006).] presented at the OECD expert meeting on farm management indicators in New Zealand in March 2004, a set of farm management indicators was presented in the framework of a typology of grazing livestock farming systems in the EU-15 (includes all Member States of the European Union before 2004). The present paper presents new results on farm management indicators within the framework of an extended typology for all farming sectors. It presents an environmentally oriented extension to the EU typology of farms currently used for assessing the situation of farming within the European Union. The extended typology is tested in relation to emerging policy issues such as environmental sustainability and rural viability by analysing some of the farm management indicators suggested in Andersen et al., [(2004a). Farming and the Environment in the European Community--using agricultural statistics to provide farm management indicators. Paper presented at OECD Expert meeting, March 2004, New Zealand. (1st of February 2006).]. Finally, recommendations in relation to the next generation EU farm typology are given.     

Evaluating livestock system environmental performance with whole-farm nutrient balance

As a part of the USEPA's concentrated animal feeding operation (CAFO) final rule, all CAFOs are required to develop and implement a nutrient management plan (NMP). The USEPA's emphasis on better management of nutrients appropriately targets a critical environmental issue associated with animal production. The concentration of animals in livestock feeding operations, often separate from feed grain production, requires importing of substantial quantities of feed nutrients. Due to the inefficiencies of nutrient utilization in livestock production, quantities of nitrogen (N) and phosphorus (P) in manure greater than can be utilized in local crop production often result. With the focus of the USEPA's NMP rules on internal farm manure management planning, nutrient concentrations resulting from animal concentration may not be adequately addressed by compliance with the USEPA rules alone. A review of two mandatory and two voluntary nutrient management strategies is made by comparing whole-farm nutrient balance for a case-study beef cattle feedlot. The results suggest that voluntary BMPs, such as modification to animal feeding program and exporting of manure, can have greater environmental benefits (30-60% reduction in P accumulation for case-study farm) than mandatory NMPs and buffers (5-7% reduction in P accumulation for case-study farm) for a typical beef cattle feedlot. Whole-farm nutrient balance procedures can also be valuable for reviewing the nutrient performance of livestock systems.     

Farmyards, an overlooked source for highly contaminated runoff

Summer sampling of storm runoff generated from areas of roofs and hardstanding situated on four dairy/beef farms has provided novel information regarding its microbiological and chemical quality. All farm hardstandings generated runoff that was contaminated with respect to those pollutants (faecal coliforms, FC, and faecal streptococci, FS, major nutrients, organic carbon) that are ubiquitously associated with faecal matter and urine. The separate analysis of roof runoff indicated that these can contribute significant concentrations of FS, phosphorus (P) and potentially toxic elements such as zinc (Zn), and suggests a level of 'background' contamination originating from wash-off of bird droppings and in the case of Zn galvanised surfaces. On average hardstanding runoff showed enhanced concentrations of >4 orders of magnitude for FC and 2-3 for major nutrients and carbon relative to roof runoff. Organic forms of nitrogen (N) and P contributed significantly (averaging >40%) to the total dissolved fraction in both roof and hardstanding runoff. Part of the substantial variability in composition of runoff samples could be attributed to differences between farms as well as the timing of sample collection during individual storms. Where situations allowed, a comparison of water upstream and downstream of the farmyard demonstrated they acted as a source of multiple contaminants not only during hydrologically active storm events but also during dry periods. Contamination pathways included a combination of both point (e.g., septic overflows) and non-point (e.g., seepage from livestock housing) sources. Farmyards situated within intensive livestock farming areas such as SW Scotland, would be expected to have significant local and accumulated downstream impacts on the aquatic environment. Localised impacts would be particularly important for headwaters and low order streams.     

An approach for measuring methane emissions from whole farms

Estimates of enteric methane (CH4) emissions from ruminants are typically measured by confining animals in large chambers, using head hoods or masks, or by a ratiometric technique involving sampling respired air of the animal. These techniques are not appropriate to evaluate large-scale farm emissions and the variability between farms that may be partly attributed to different farm management. This study describes the application of an inverse-dispersion technique to calculate farm emissions in a controlled tracer-release experiment. Our study was conducted at a commercial dairy farm in southern Alberta, Canada (total of 321 cattle, including 152 lactating dairy cows). Sulfur hexafluoride (SF6) and CH4 were released from 10 outlet locations (barn and open pens) using mass-flow controllers. A Lagrangian stochastic (LS) dispersion model was then used to infer farm emissions from downwind gas concentrations. Concentrations of SF6 and CH4 were measured by gas chromatography analysis and open path lasers, respectively. Wind statistics were measured with a three-dimensional sonic anemometer. Comparing the inferred emissions with the known release rate showed we recovered 86% of the released CH4 and 100% of the released SF6. The location of the concentration observations downwind of the farm was critically important to the success of this technique.