Prediction of odor from pig production based on chemical odorants

The present work was performed to investigate the use of odorant measurements for prediction of odor concentration in facilities with growing-finishing pigs and to analyze the odorant composition in facilities with different floor and ventilation systems. Air was sampled in Nalophan bags, odor concentrations were measured by dilution-to-threshold olfactometry, and concentrations of odorants were measured by proton-transfer-reaction mass spectrometry (PTR-MS). Olfactometry and chemical analyses were synchronized to take place at identical time intervals after sampling. A principal component analysis revealed that different facilities for growing-finishing pigs can be distinguished based on the odorants. Pit ventilation comprising a small amount of the total ventilation air (10-20%) in facilities with both room and pit ventilation can be used to concentrate odorants, whereas the room ventilation contains lower concentrations of most odorants. A partial least squares regression model demonstrated that prediction of the odor concentration based on odorants measured by PTR-MS is feasible. Hydrogen sulfide, methanethiol, trimethylamine, and 4-methylphenol were identified as the compounds having the largest influence on the prediction of odor concentration, whereas carboxylic acids had no significant influence. In conclusion, chemical measurement of odorants by PTR-MS is an alternative for expressing the odor concentration in facilities with growing-finishing pigs that can be used to increase the understanding of odor from different types of facilities and improve the development of odor reduction technologies.     

Evaluation of zeolite for control of odorants emissions from simulated poultry manure storage

Poultry operations are associated with emissions of aerial ammonia (NH3), volatile organic compounds (VOCs), and odor, and the magnitude of emissions is influenced by manure management practices. As a manure treatment additive, zeolites have been shown to have the potential to control NH3. Because of their properties it is also expected that zeolites could effectively adsorb VOCs and odor. The effectiveness of zeolite in controlling odor and VOCs was qualitatively evaluated in this controlled laboratory study involving simulated poultry manure storage. In the first two trials, zeolite was topically applied on nearly fresh laying hen manure at the rates of 0, 2.5, 5, and 10% (by weight). In the third trial, zeolite was topically applied at 5% with each addition of fresh manure into the storage vessel. Headspace samples from the emission vessels were collected with solid phase microextraction (SPME) and analyzed on a multidimensional-gas chromatograph-mass spectrometry-olfactometry (MDGC-MS-O) system for identification and prioritization of poultry manure odorants. Acetic acid, butanoic acid, isovaleric acid, indole, and skatole were consistently controlled in the headspace, with the reduction rate being proportional to the zeolite application rate. Dimethyl trisulfide and phenol were consistently generated, and with a few exceptions, the rate of generation was proportional to the application rate. Average reduction of the odor caused by all odorants evaluated with SPME-GC-O was 67% (+/-12%) and 51% (+/-26%) for the two topical applications, respectively, while no significant reduction of VOCs and odor was detected for the layered application.     

Swine odor analyzed by odor panels and chemical techniques

The National Research Council identified odors as a significant animal emission and highlighted the need to develop standardized protocols for sampling and analysis. The purpose of our study was to compare different odor sampling techniques for monitoring odors emitted from stored swine manure. In our study, odorous headspace air from swine manure holding tanks were analyzed by human panels and analytical techniques. Odorous air was analyzed by human panels using dynamic dilution olfactometry (DDO). Chemical analysis used acid traps for ammonia (NH?), fluorescence for hydrogen sulfide (H?S), and thermal desorption gas chromatography-mass spectrometry for volatile organic compounds (VOCs). Chemical analysis included the use of gas chromatography-olfactometry (GC-O) for determining key odorants. Chemical odorant concentrations were converted to odor activity values (OAVs) based on literature odor thresholds. The GC-O technique used was GC-SNIF. Dilution thresholds measured by different odor panels were significantly different by almost an order of magnitude even though the main odorous compound concentrations had not changed significantly. Only 5% of the key odorous VOCs total OAVs was recovered from the Tedlar bags used in DDO analysis. Ammonia was the only chemical odorant significantly correlated with DDO analysis in the fresh (1 wk) and aged manure. Chemical analysis showed that odor concentration stabilized after 5 to 7 wk and that HS was the most dominant odorant. In aged manure, neither volatile fatty acids (VFAs) nor HS was correlated with any other chemical odorant, but NH, phenols, and indoles were correlated, and phenols and indoles were highly correlated. Correlation of odorant concentration was closely associated with the origin of the odorant in the diet. Key odorants determined by chemical and GC-O included indoles, phenols, NH?, and several VFAs (butanoic, 3-methylbutanoic, and pentanoic acids).     

Correlation of human olfactory responses to airborne concentrations of malodorous volatile organic compounds emitted from swine effluent

Direct multicomponent analysis of malodorous volatile organic compounds (VOCs) present in ambient air samples from 29 swine (Sus scrofa) production facilities was used to develop a 19-component artificial swine odor solution that simulated olfactory properties of swine effluent. Analyses employing either a human panel consisting of 14 subjects or gas chromatography were performed on the air stream from an emission chamber to assess human olfactory responses or odorant concentration, respectively. Analysis of the olfactory responses using Fisher's LSD statistics showed that the subjects were sensitive to changes in air concentration of the VOC standard across dilutions differing by approximately 16%. The effect of chemical synergisms and antagonisms on human olfactory response magnitudes was assessed by altering the individual concentration of nine compounds in artificial swine odor over a twofold concentration range while maintaining the other 18 components at a constant concentration. A synergistic olfactory response was observed when the air concentration of acetic acid was increased relative to the concentration of other VOC odorants in the standard. An antagonistic olfactory response was observed when the air concentration of 4-ethyl phenol was increased relative to the other VOC odorants in the standard. The collective odorant responses for nine major VOCs associated with swine odor were used to develop an olfactory prediction model to estimate human odor response magnitudes to swine manure odorants through measured air concentrations of indicator VOCs. The results of this study show that direct multicomponent analysis of VOCs emitted from swine effluent can be applied toward estimating perceived odor intensity.     

Field olfactometry assessment of dairy manure land application methods

Surface application of manure in reduced tillage systems generates nuisance odors, but their management is hindered by a lack of standardized field quantification methods. An investigation was undertaken to evaluate odor emissions associated with various technologies that incorporate manure with minimal soil disturbance. Dairy manure slurry was applied by five methods in a 3.5-m swath to grassland in 61-m-inside-diameter rings. Nasal Ranger Field Olfactometer (NRO) instruments were used to collect dilutions-to-threshold (D/T) observations from the center of each ring using a panel of four odor assessors taking four readings each over a 10-min period. The Best Estimate Threshold D/T (BET10) was calculated for each application method and an untreated control based on preapplication and <1 h, 2 to 4 h, and approximately 24 h after spreading. Whole-air samples were simultaneously collected for laboratory dynamic olfactometer evaluation using the triangular forced-choice (TFC) method. The BET10 of NRO data composited for all measurement times showed D/T decreased in the following order (a = 0.05): surface broadcast > aeration infiltration > surface + chisel incorporation > direct ground injection Sshallow disk injection > control, which closely followed laboratory TFC odor panel results (r = 0.83). At 24 h, odor reduction benefits relative to broadcasting persisted for all methods except aeration infiltration, and odors associated with direct ground injection were not different from the untreated control. Shallow disk injection provided substantial odor reduction with familiar toolbar equipment that is well adapted to regional soil conditions and conservation tillage operations.     

Odorants and malodors associated with land application of biosolids stabilized with lime and coal fly ash

Malodor emissions limit public acceptance of using municipal biosolids as natural organic resources in agricultural production. We aimed to identify major odorants and to evaluate odor concentrations associated with land application of anaerobically digested sewage sludges (Class B) and their alkaline (lime and coal fly ash)-stabilized products (Class A). These two types of biosolids were applied at 12.6 tonnes ha(-1) (dry weight) to microplots of very fine clayey Vertisol in the Jezreel Valley, northern Israel. The volatile organic compounds (VOCs) emitted from the biosolids before and during alkaline stabilization and after incorporation into the soil were analyzed by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry. Odor concentrations at the plots were evaluated on site with a Nasal Ranger field olfactometer that sniffed over a defined land surface area through a static chamber. The odors emitted by anaerobically digested sewage sludges from three activated sludge water treatment plants had one characteristic chemical fingerprint. Alkaline stabilization emitted substantial odors associated with high concentrations of ammonia and release of nitrogen-containing VOCs and did not effectively reduce the potential odor annoyance. Odorous VOCs could be generated within the soil after biosolids incorporation, presumably because of anaerobic conditions within soil-biosolids aggregates. We propose that dimethyl disulfide and dimethyl trisulfide, which seem to be most related to the odor concentrations of biosolids-treated soil, be used as potential chemical markers for the odor annoyance associated with incorporation of anaerobically digested sewage sludges.     

Odor and gas release from anaerobic treatment lagoons for swine manure

Odor and gas release from anaerobic lagoons for treating swine waste affect air quality in neighboring communities but rates of release are not well documented. A buoyant convective flux chamber (BCFC) was used to determine the effect of lagoon loading rate on measured odor and gas releases from two primary lagoons at a simulated wind speed of 1.0 m s(-1). Concentrations of ammonia (NH3), hydrogen sulfide (H2S), carbon dioxide (CO2), sulfur dioxide (SO2), and nitric oxide (NO) in 50-L air samples were measured. A panel of human subjects, whose sensitivity was verified with a certified reference odorant, evaluated odor concentration, intensity, and hedonic tone. Geometric mean odor concentrations of BCFC inlet and outlet samples and of downwind berm samples were 168 +/- 44 (mean +/- 95% confidence interval), 262 +/- 60, and 114 +/- 38 OU(E) m(-3) (OU(E), European odor unit, equivalent to 123 microg n-butanol), respectively. The overall geometric mean odor release was 2.3 +/- 1.5 OU(E) s(-1) m(-2) (1.5 +/- 0.9 OU s(-1) m(-2)). The live mass specific geometric mean odor release was 13.5 OU(E) s(-1) AU(-1) (animal unit = 500 kg live body mass). Overall mean NH3, H2S, CO2 and SO2 releases were 101 +/- 24, 5.7 +/- 2.0, 852 +/- 307, and 0.5 +/- 0.4 microg s(-1) m(-2), respectively. Nitric oxide was not detected. Odor concentrations were directly proportional to H2S and CO2 concentrations and odor intensity, and inversely proportional to hedonic tone and SO2 concentration (P < 0.05). Releases of NH3, H2S, and CO2 were directly proportional (P < 0.05) to volatile solids loading rate (VSLR).     

Stability of odorants from pig production in sampling bags for olfactometry

Odor from pig production facilities is typically measured with olfactometry, whereby odor samples are collected in sampling bags and assessed by human panelists within 30 h. In the present study, the storage stability of odorants in two types of sampling bags that are often used for olfactometry was investigated. The bags were made of Tedlar or Nalophan. In a field experiment, humid and dried air samples were collected from a pig production facility with growing-finishing pigs and analyzed with a gas chromatograph with an amperometric sulfur detector at 4, 8, 12, 28, 52, and 76 h after sampling. In a laboratory experiment, the bags were filled with a humid gas mixture containing carboxylic acids, phenols, indoles, and sulfur compounds and analyzed with proton-transfer-reaction mass spectrometry after 0, 4, 8, 12, and 24 h. The results demonstrated that the concentrations of carboxylic acids, phenols, and indoles decreased by 50 to >99% during the 24 h of storage in Tedlar and Nalophan bags. The concentration of hydrogen sulfide decreased by approximately 30% during the 24 h of storage in Nalophan bags, whereas in Tedlar bags the concentration of sulfur compounds decreased by <5%. In conclusion, the concentrations of odorants in air samples from pig production facilities significantly decrease during storage in Tedlar and Nalophan bags, and the composition changes toward a higher relative presence of sulfur compounds. This can result in underestimation of odor emissions from pig production facilities and of the effect of odor reduction technologies.     

A solid-phase microextraction chamber method for analysis of manure volatiles

Odors from livestock operations are a complex mixture of volatile carbon, sulfur, and nitrogen compounds. Currently, detailed volatiles analysis is both time consuming and requires specialized equipment and methods. This work describes a new method that utilizes a dynamic flux chamber, solid-phase microextraction (SPME), and gas chromatography-mass spectroscopy (GC-MS) to describe and compare the odorous compounds emitted from cattle and swine feces. Evaluation of method parameters produced a protocol for comparing relative emissions based on fixed sample temperature (20 degrees C) and exposed surface area (approximately 523 cm(2)), air flow rates (1 L min(-1) or 16 cm s(-1)), SPME exposure time (5 min), and chamber cleaning procedures (70% ethanol rinse and drying for 30 min at 105 degrees C) to minimize cross-contamination between samples. A variety of volatile organic compounds (VOCs) including alcohols, volatile fatty acids, aromatic ring compounds, ketones, esters, and sulfides were routinely detected and the relative emissions from fresh and incubated (37 degrees C overnight) swine and cattle feces were compared as a measure of potential to produce odorants during manure storage. Differences in the types and relative quantities of volatiles emitted were detected when animal species (cattle or swine), diet, fecal incubation, or sample storage conditions (20, 4, or -20 degrees C) were varied.     

Measuring flux of soil fumigants using the aerodynamic and dynamic flux chamber methods

Methods for measuring and estimating flux density of soil fumigants under field conditions are important for the purpose of providing inputs to air dispersion models and for comparing the effects of management practices on emission reduction. The objective of this study was to measure the flux of 1,3-dichloropropene (1,3-D) and chloropicrin at a site in Georgia (GA) using the aerodynamic method and the dynamic flux chamber (FC) method. A secondary objective was to compare the effects of high density polyethylene (HDPE), and virtually impermeable film (VIF) tarps on fumigant flux at a site in Florida (FL). Chloropicrin and 1,3-D were applied by surface drip application of In-Line soil fumigant on vegetable beds covered by low density polyethylene (LDPE), HDPE, or VIF. The surface drip fumigation using In-Line and LDPE tarp employed in this study resulted in volatilization of 26.5% of applied 1,3-D and 11.2% of the applied chloropicrin at the GA site, as determined using the aerodynamic method. Estimates of mass loss obtained from dynamic FCs were 23.6% for 1,3-D and 18.0% for chloropicrin at the GA site. Flux chamber trials at the FL site indicate significant additional reduction in flux density, and cumulative mass loss when VIF tarp is used. This study supports the use of dynamic FCs as a valuable tool for estimating gas flux density from agricultural soils, and evaluating best management practices for reducing fumigant emissions to the atmosphere.     

Calculating the detection limits of chamber-based soil greenhouse gas flux measurements

Renewed interest in quantifying greenhouse gas emissions from soil has led to an increase in the application of chamber-based flux measurement techniques. Despite the apparent conceptual simplicity of chamber-based methods, nuances in chamber design, deployment, and data analyses can have marked effects on the quality of the flux data derived. In many cases, fluxes are calculated from chamber headspace vs. time series consisting of three or four data points. Several mathematical techniques have been used to calculate a soil gas flux from time course data. This paper explores the influences of sampling and analytical variability associated with trace gas concentration quantification on the flux estimated by linear and nonlinear models. We used Monte Carlo simulation to calculate the minimum detectable fluxes (α = 0.05) of linear regression (LR), the Hutchinson/Mosier (H/M) method, the quadratic method (Quad), the revised H/M (HMR) model, and restricted versions of the Quad and H/M methods over a range of analytical precisions and chamber deployment times (DT) for data sets consisting of three or four time points. We found that LR had the smallest detection limit thresholds and was the least sensitive to analytical precision and chamber deployment time. The HMR model had the highest detection limits and was most sensitive to analytical precision and chamber deployment time. Equations were developed that enable the calculation of flux detection limits of any gas species if analytical precision, chamber deployment time, and ambient concentration of the gas species are known.     

Functional classification of swine manure management systems based on effluent and gas emission characteristics

Gaseous emissions from swine (Sus scrofa) manure storage systems represent a concern to air quality due to the potential effects of hydrogen sulfide, ammonia, methane, and volatile organic compounds on environmental quality and human health. The lack of knowledge concerning functional aspects of swine manure management systems has been a major obstacle in the development and optimization of emission abatement technologies for these point sources. In this study, a classification system based on gas emission characteristics and effluent concentrations of total phosphorus (P) and total sulfur (S) was devised and tested on 29 swine manure management systems in Iowa, Oklahoma, and North Carolina in an effort to elucidate functional characteristics of these systems. Four swine manure management system classes were identified that differed in effluent concentrations of P and S, methane (CH4) emission rate, odor intensity, and air concentration of volatile organic compounds (VOCs). Odor intensity and the concentration of VOCs in air emitted from swine manure management systems were strongly correlated (r2 = 0.88). The concentration of VOC in air samples was highest with outdoor swine manure management systems that received a high input of volatile solids (Type 2). These systems were also shown to have the highest odor intensity levels. The emission rate for VOCs and the odor intensity associated with swine manure management systems were inversely correlated with CH4 and ammonia (NH3) emission rates. The emission rates of CH4, NH3, and VOCs were found to be dependent upon manure loading rate and were indirectly influenced by animal numbers.     

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.     

Examination of Salmonella and Escherichia coli translocation from hog manure to forage, soil, and cattle grazed on the hog manure-treated pasture

Use of hog (Sus scrofa) manure as a fertilizer is a practical solution for waste re-utilization, however, it may serve as a vehicle for environmental and domestic animal contamination. Work was conducted to determine whether pathogens, naturally present in hog manure could be detected in cattle (Bos taurus) grazed on the manure-treated pasture, and whether forage contamination occurred. During two 3 mo summer trials manure was applied to yield < or = 124 kg available N per hectare in a single spring or split spring and fall application. Samples of hog manure, forage, soil, and cattle feces were analyzed for naturally occurring Salmonella, Yersinia enterocolitica, and Escherichia coli. To follow movement of Salmonella in the environment isolates were identified to serovar and serotyped. Transfer of E. coli from hog manure to soil and cattle was examined by randomly amplified polymorphic DNA (RAPD) analysis of >600 E. coli isolates. While Y. enterocolitica was absent from all samples, in both years S. enterica Derby and S. enterica Krefeld were found in most hog manure samples, but were only on forage samples in the second year. Salmonella enterica Typhimurium, absent from hog manure was present on some forage in the first year. Cattle feces and soil samples were consistently Salmonella negative. These contaminations could not be traced to manure application. During this study, Salmonella and E. coli found in hog manure had different RAPD genomic profiles from those found in the feces of cattle grazing on manure-treated pasture.     

Reducing crude protein in beef cattle diet reduces ammonia emissions from artificial feedyard surfaces

Concentrated animal feeding operations are major sources of ammonia to the atmosphere. Control methods to reduce emissions include acidifying amendments, urease inhibitors, and absorbents. For beef cattle, decreasing crude protein (CP) in diets may be the most practical and cost-effective method to reduce ammonia emissions. Our objective was to quantify the effect of reducing CP in beef cattle diet on ammonia emissions. Two groups of steers were fed diets with either 11.5 or 13.0% CP and all urine and feces were collected. Manures from the two diet treatments were applied in a replicated laboratory chamber experiment, and ammonia emission was quantified using acid gas washing. In four seasonal field trials, manures from the two diet treatments were applied to two 10-m-diameter, circular, artificial feedyard surfaces, and ammonia emission was quantified using the integrated horizontal flux method. Manure from steers fed 11.5% CP diet had less urine, less urinary N, and a lesser fraction of total N in urine, compared with the 13.0% CP diet. Decreasing crude protein in beef cattle diets from 13 to 11.5% significantly decreased ammonia emission by 44% (p < 0.01) in the closed chamber laboratory experiment, and decreased mean daily ammonia flux by 30% (p = 0.10), 52% (p = 0.08), and 29% (p < 0.01) in summer, autumn, and spring field trials, respectively. No difference was observed in winter. On an annual basis, decreasing crude protein reduced daily ammonia flux by 28%. Reducing crude protein in beef cattle diets may provide the most practical and cost-effective way to reduce ammonia emissions from feedyards.     

Demonstration of methods to reduce E. coli runoff from dairy manure application sites

Contamination by bacteria is a leading cause of impairment in U.S. waters, particularly in areas of livestock agriculture. We evaluated the effectiveness of several practices in reducing Escherichia coli levels in runoff from fields receiving liquid dairy (Bos taurus) manure. Runoff trials were conducted on replicated hay and silage corn (Zea mays L.) plots using simulated rainfall. Levels of E. coli in runoff were approximately 10(4) to 10(6) organisms per 100 mL, representing a significant pollution potential. Practices tested were: manure storage, delay between manure application and rainfall, manure incorporation by tillage, and increased hayland vegetation height. Storage of manure for 30 d or more consistently and dramatically lowered E. coli counts in our experiments, with longer storage providing greater reductions. Manure E. coli declined by > 99% after approximately 90 d of storage. On average, levels of E. coli in runoff were 97% lower from plots receiving 30-d-old and > 99% lower from plots receiving 90-d-old manure than from plots where fresh manure was applied. Runoff from hayland and cornland plots where manure was applied 3 d before rainfall contained approximately 50% fewer E. coli than did runoff from plots that received manure 1 d before rainfall. Hayland vegetation height alone did not significantly affect E. coli levels in runoff, but interactions with rainfall delay and manure age were observed. Manure incorporation alone did not significantly affect E. coli levels in cornland plot runoff, but incorporation could reduce bacteria export by reducing field runoff and interaction with rainfall delay was observed. Extended storage that avoids additions of fresh manure, combined with application several days before runoff, incorporation on tilled land, and higher vegetation on hayland at application could substantially reduce microorganism loading from agricultural land.     

Phosphorus losses in simulated rainfall runoff from manured soils of Alberta

Manure applied to agricultural land at rates that exceed annual crop nutrient requirements can be a source of phosphorus in runoff. Manure incorporation is often recommended to reduce phosphorus losses in runoff. A small plot rainfall simulation study was conducted at three sites in Alberta to evaluate the effects of manure rate and incorporation on phosphorus losses. Treatments consisted of three solid beef cattle manure application rates (50, 100, and 200 kg ha(-1) total phosphorus), an unmanured control, and two incorporation methods (nonincorporated and incorporated with one pass of a double disk). Simulated rain was applied to soils with freshly applied and residual (1 yr after application) manure at 70 mm h(-1) to produce 30 min of runoff. Soil test phosphorus (STP), total phosphorus (TP), and dissolved reactive phosphorus (DRP) concentrations in runoff increased with manure rate for fresh and residual manure. Initial abstraction and runoff volumes did not change with manure rate. Initial abstraction, runoff volumes, and phosphorus concentrations did not change with manure incorporation at Lacombe and Wilson, but initial abstraction volumes increased and runoff volumes and phosphorus concentrations decreased with incorporation of fresh manure at Beaverlodge. Phosphorus losses in runoff were directly related to phosphorus additions. Extraction coefficients (slopes of the regression lines) for the linear relationships between residual manure STP and phosphorus in runoff were 0.007 to 0.015 for runoff TP and 0.006 to 0.013 for runoff DRP. While incorporation of manure with a double disk had no significant effect on phosphorus losses in runoff from manure-amended soils 1 yr after application, incorporation of manure is still recommended to control nitrogen losses, improve crop nutrient uptake, and potentially reduce odor concerns.     

Organic agriculture and nitrous oxide emissions at sub-zero soil temperatures

In the Red River Valley of the upper midwestern United States, soil temperatures often remain below freezing during winter and N2O emissions from frozen cropland soils is assumed to be negligible. This study was conducted to determine the strength of N2O emissions and denitrification when soil temperatures were below zero for a manure-amended, certified organic field (T2O) compared with an unamended, conventionally managed field (T2C). Before manure application, both fields were similar with respect to autotrophic and heterotrophic N2O production and N2O flux at the soil surface (0.15+/-0.05 mg N2O-N m-2 d-1 for T2O and 0.12+/-0.06 mg N2O-N m-2 d-1 for T2C). After application of pelletized, dehydrated manure, average daily flux (based on time-integrated fluxes from 20 November to 8 April), was 1.19+/-0.34 mg N2O-N m-2 d-1 for T2O and 0.47+/-0.37 mg N2O-N m-2 d-1 for T2C. Denitrification for intact cores measured in the laboratory at -2.5 degrees C was greater for organically managed soils, although only marginally significant (p<0.1). Cumulative emissions for all winter measurements (from 16 November to 8 April) averaged 1.63 kg N2O-N ha-1 for T2O and 0.64 kg N2O-N ha-1 for T2C. Biological N2O production was evident at sub-zero soil temperatures, with winter emissions exceeding those measured in late summer. Late autumn manure application enhanced cumulative N2O-N emissions by 0.9 kg ha-1.     

Feasibility and costs of phosphorus application limits on 39 U.S. swine operations

Concerns about manure P and water quality have prompted new regulations imposing P limits on land application of manure. Previous research established that P limits increase land needs for animal feeding operations. We evaluated the effect of N, annual P, and rotation P limits on the feasibility of manure management. A mechanistic model characterized manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Extensive information collected from each operation was used to determine effects of manure storage type, ownership structure, and application limits on attributes of manure management. Phosphorus limits had substantially greater effect on slurry operations, increasing land needs 250% (0.3 hectares per animal unit [AU]) and time for manure application 24% (2.5 min AU(-1)) for rotation P limits and 41% (4.4 min AU(-1)) for annual P limits. Annual P limits were infeasible for current land application equipment on two operations and had the greatest effect on time and costs because they required all but three slurry operations to reduce discharge rate. We recommend implementing rotation P limits (not to exceed crop N need) to minimize time effects, allow most farmers to use their current manure application methods, and allow manure to fulfill crop N and P needs in the year of application. Phosphorus limits increased potential manure value but would require slurry operations to recover at least 61% of manure value through manure sales. Phosphorus limits are likely to shape the U.S. swine industry through differential effects on the various sectors of the swine industry.     

An assessment of nitrogen-based manure application rates on 39 U.S. swine operations

Water quality concerns and revised regulations are changing how confined animal feeding operations manage manure. Devising acceptable and feasible changes in manure practices requires a full understanding of the forces shaping current manure management decisions. Previous theoretical models have shown that a wide range of factors influence the lowest cost solution for manure management. We used a mechanistic model to characterize the manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Information was collected from each operation about animal numbers, feed and water use, manure handling and storage characteristics, field locations, crop rotation, fertilizer need, and equipment inventory and usage. Collected data were used as input and to validate results from a mechanistic model that determined acres required for manure application, manure application rate, time required for manure application, value of manure, and costs of manure management. The 39 farms had a mean of 984 animal units (AU) per operation, 18.2 AU ha(-1) (7.4 AU acre(-1)), and manure application costs of dollar 10.49 AU(-1) yr(-1). Significant factors affecting manure management included operation size, manure handling system, state, and ownership structure. Larger operations had lower manure management costs (r2 = 0.32). Manure value potentially exceeded manure application costs on 58% of slurry and 15% of lagoon operations. But 38% of slurry operations needed to apply manure off the farm whereas all lagoon operations had sufficient land for N-based manure management. Manure management was a higher percentage of gross income on contract operations compared with independents (P < 0.01). This research emphasized the importance of site-specific factors affecting manure management decisions and the economics of U.S. swine operations.