Determination of steroidal estrogens in flushed dairy manure wastewater by gas chromatography-mass spectrometry

There is a critical need to accurately measure the concentrations of natural steroidal estrogens in flushed dairy manure wastewater (FDMW) to assess any potential risk of waterway contamination resulting from land application. Estrogens are a concern because low concentrations (10-100 ng L-1) in water can adversely affect aquatic vertebrate species such as fish, turtles, and frogs by disrupting the normal function of their endocrine systems. The objective of this study was to develop a sample preparation method that permits the quantification of four natural steroidal estrogens (17alpha-estradiol, 17beta-estradiol, estrone, and estriol) in FDMW by gas chromatography-mass spectrometry (GC-MS). Solid-phase extraction with graphitized carbon black was used for the bulk extraction of estrogens from FDMW and additional sample purification was accomplished with C-18. The sample preparation method allowed estrogens to be detected accurately by GC-MS in FDMW. Spiked recovery experiments indicated that the method is satisfactory for measuring the estrogens of interest in FDMW with average recovery of >90%. As expected in FDMW, characterization of the estrogen profile revealed a large abundance of 17alpha-estradiol relative to 17beta-estradiol and estrone. Estriol was not detected in FDMW. The methodology developed in this research helps provide an analytical foundation for the quantification of steroidal estrogens in FDMW by GC-MS.     

Free and conjugated estrogen exports in surface-runoff from poultry litter-amended soil

Land application of animal manures such as poultry litter is a common practice, especially in states with surplus manure. Past studies have shown that animal manure may contain estrogens, which are classified as endocrine-disrupting chemicals and may pose a threat to aquatic and wildlife species. We evaluated the concentrations of estrogens in surface runoff from experimental plots (5 x 12 m each) receiving raw and pelletized poultry litter. We evaluated the free (estrone, E1; 17beta-estradiol, E2beta; estriol, E3) and conjugate forms (glucuronides and sulfates) of estrogens, which differ in their toxicity. Sampling was performed for 10 natural storm events over a 4-mo period (April-July 2008). Estrogen concentrations were screened using enzyme-linked immunosorbent assay (ELISA), followed by quantification using liquid chromatography with tandem mass spectrometry (LC/MS/MS). Concentrations of estrogens from ELISA were much higher than the LC/MS/MS values, indicating crossreactivity with organic compounds. Exports of estrogens were much lower from soils amended with pelletized poultry litter than the raw form of the litter. No-tillage management practice also resulted in a lower export of estrogens with surface runoff compared with reduced tillage. The concentrations and exports of conjugate forms of estrogens were much higher than the free forms for some treatments, indicating that the conjugate forms should be considered for a comprehensive assessment of the threat posed by estrogens.     

Decrease in water-soluble 17beta-Estradiol and testosterone in composted poultry manure with time

Little attention has been paid to the environmental fate of the hormones 17beta-estradiol and testosterone excreted in animal waste. Land application of manure has a considerable potential to affect the environment with these endocrine disrupting compounds (EDCs). Composting is known to decompose organic matter to a stable, humus-like material. The goal of the present study was to quantitatively assess levels of water-soluble 17beta-estradiol and testosterone in composting chicken manure with time. Chicken layer manure was mixed with hay, straw, decomposed leaves, and starter compost, adjusted to approximately 60% moisture, and placed into a windrow. A clay-amended windrow was also prepared. Windrows were turned weekly, and temperature, oxygen, and CO(2) in the composting mass were monitored for either 133 or 139 d. Commercial enzyme immunoassay kits were used to quantitate the levels of 17beta-estradiol and testosterone in aqueous sample extracts. Water-soluble quantities of both hormones diminished during composting. The decrease in 17beta-estradiol followed first-order kinetics, with a rate constant k = -0.010/d. Testosterone levels declined at a slightly higher rate than 17beta-estradiol (i.e., k = -0.015/d). Both hormones could still be measured in aqueous extracts of compost sampled at the conclusion of composting. The decline in water-soluble 17beta-estradiol and testosterone in extracts of clay-amended compost was not statistically different from normal compost. These data suggest that composting may be an environmentally friendly technology suitable for reducing, but not eliminating, the concentrations of these endocrine disrupting hormones at concentrated animal operation facilities.     

Persistence of testosterone and 17beta-estradiol in soils receiving swine manure or municipal biosolids

Natural and synthetic steroidal hormones can be carried to agricultural soil through fertilization with municipal biosolids, livestock manure, or poultry manure. The persistence and pathways of dissipation of [4-(14)C]-testosterone and of [4-(14)C]-17beta-estradiol in organic-amended soils were investigated using laboratory microcosms. Testosterone dissipation was investigated over a range of amendment concentrations, temperatures, and soil types. Under all conditions the parent compound and transformation products were dissipated within a few days. Addition of swine manure slurry to soil hastened the transformation of testosterone and 17beta-estradiol to the corresponding less hormonally active ketones, 4-androstene-3,17-dione and estrone. Two other testosterone transformation products, 5alpha-androstan-3,17-dione and 1,4-androstadiene-3,17-dione, were also detected. Experiments with sterilized soil and sterilized swine manure slurry suggested that the transformation of (14)C-labeled hormonal parent compounds was mainly caused by microorganisms in manure slurry, while mineralization of the hormones to (14)CO(2) required viable soil microorganisms. Organic amendments transiently inhibited the mineralization of [4-(14)C]-testosterone, perhaps by inhibiting soil microorganisms, or by enhancing sorption and reducing the bioavailability of testosterone or transformation products. Overall, organic amendments influenced the pathways and kinetics of testosterone and estradiol dissipation, but did not increase their persistence.     

Sorption, mobility, and transformation of estrogenic hormones in natural soil

Potent estrogenic hormones are consistently detected in the environment at low concentration, yet these chemicals are strongly sorbed to soil and are labile. The objective of this research was to improve the understanding of the processes of sorption, mobility, and transformation for estrogens in natural soils, and their interaction. Equilibrium and kinetic batch sorption experiments, and a long-term column study were used to study the fate and transport of 17beta-estradiol and its primary metabolite, estrone, in natural soil. Kinetic and equilibrium batch experiments were done using radiolabeled 17beta-estradiol and estrone. At the concentrations used, it appeared that equilibrium sorption for both estrogens was achieved between 5 and 24 h, and that the equilibrium sorption isotherms were linear. The log K(oc) values for 17beta-estradiol (2.94) and estrone (2.99) were consistent with previously reported values. Additionally, it was found that there was rate-limited sorption for both 17beta-estradiol (0.178 h(-1)) and estrone (0.210 h(-1)). An approximately 42 h long, steady-flow, saturated column experiment was used to study the transport of radiolabeled 17beta-estradiol, which was applied in a 5.00 mg L(-1) solution pulse for 44 pore volumes. 17beta-estradiol and estrone were the predominant compounds detected in the effluent. The effluent breakthrough curves were asymmetric and the transport modeling indicated that sorption was rate-limited. Sorption rates and distributions of the estrogens were in agreement between column and batch experiments. This research can provide a better link between the laboratory results and observations in the natural environment.     

Toxicity of ozonated animal manure to the house fly, Musca domestica

Swine manure slurries were ozonated at a dosage of 1 g/L and tested for their toxicity to the house fly (Musca domestica). The observed toxicity of ozonated swine manure was consistent and independent of origin of the swine manure. A dose (dilution) response curve was performed. A 50% dilution in the ozonated swine manure slurry resulted in 90% reduction in toxicity. Neither the synthetic nor ozonated synthetic swine manure, both of which contained higher concentrations of formaldehyde and three other unidentified carbonyl compounds than the ozonated swine manure, were toxic to the flies. Ozonated swine manure slurry was centrifuged and passed through a 0.45-microm filter. The liquid phase was as toxic as the unfiltered slurry; as such, the toxicant appears to be present in liquid phase. Neither ammonia, hydrogen sulfide, formaldehyde, nor other simple aldehydes appeared to be the toxic agent. The toxic agent appears to be a polar chemical compound and is concentrated in the urine. Several possible compounds have been identified. The toxicity of untreated and ozonated manure slurries from different livestock was compared. Six animal manure slurries (beef and dairy cattle, horse, poultry, sheep, and swine) were ozonated (dosage of 1 g/L) and tested for toxicity to the house fly. Ozonated dairy cattle manure slurry showed 78% mortality after 72 h, whereas ozonated swine manure slurry achieved a 100% mortality rate in 48 h. Neither the unozonated dairy nor swine manure slurries, nor any of the other raw or ozonated manure slurries, were toxic to the flies.     

Dissipation of 17β-estradiol in composted poultry litter

The excreted estrogen rate of all livestock in the United States is estimated at 134 kg d. The influence of manure treatment on the fate of estrogens is critical in deciding the recycling of over 300 million dry tons of livestock produced annually. The effects of two common manure management practices, heated composting and ambient temperature decomposition, on the fate of 17β-estradiol in poultry litter were determined. A mixture of poultry litter, wood chips, and straw was amended with [C]17β-estradiol and allowed to undergo decomposition with a laboratory-scale heated composter (HC) or room temperature incubation (RTI) for 24 d. Radiolabel in the finished products was fractionated into water-extractable, acetone-extractable, nonextractable, and mineralized fractions. Total 17β-estradiol radioactive residues in the HC and RTI ( = 2) treatments were not different ( > 0.05), except that statistically less 17β-estradiol was mineralized to CO during HC than RTI (1.1 vs. 10.0% for HC and RTI, respectively). Estrone was the major degradation product in extracts of HC and RTI treatments as determined by liquid chromatography/mass spectrometry analyses. The nonextractable residues indicated no quantitative differences among the humins between the treatments. An estimated 3% of the fortified estrogenicity remained after HC treatment, and 15% of the fortified estrogenicity remained after RTI treatment. If reduction of water-removable, biologically active 17β-estradiol is the treatment goal, then HC treatment would be slightly preferred over ambient temperature degradation. However, unmanaged, ambient temperature litter piles are less costly and time consuming for food animal producers and result in greater mineralization and similar immobilization of estradiol.     

Antibiotic degradation during manure composting

On-farm manure management practices, such as composting, may provide a practical and economical option for reducing antibiotic concentrations in manure before land application, thereby minimizing the potential for environmental contamination. The objective of this study was to quantify degradation of chlortetracycline, monensin, sulfamethazine, and tylosin in spiked turkey (Meleagris gallopavo) litter during composting. Three manure composting treatments were evaluated: a control treatment (manure pile with no disturbance or adjustments after initial mixing), a managed compost pile (weekly mixing and moisture content adjustments), and vessel composting. Despite significant differences in temperature, mass, and nutrient losses between the composting treatments and the control, there was no difference in antibiotic degradation among the treatments. Chlortetracycline concentrations declined rapidly during composting, whereas monensin and tylosin concentrations declined gradually in all three treatments. There was no degradation of sulfamethazine in any of treatments. At the conclusion of the composting period (22-35 d), there was >99% reduction in chlortetracycline, whereas monensin and tylosin reduction ranged from 54 to 76% in all three treatments. Assuming first-order decay, the half-lives for chlortetracycline, monensin, and tylosin were 1, 17, and 19 d, respectively. These data suggest that managed compositing in a manure pile or in a vessel is not better than the control treatment in degrading certain antibiotics in manure. Therefore, low-level manure management, such as stockpiling, after an initial adjustment of water content may be a practical and economical option for livestock producers in reducing antibiotic levels in manure before land application.     

Season and bedding impacts on ammonia emissions from tie-stall dairy barns

Federal and state regulations are being promulgated under the Clean Air Act to reduce hazardous air emissions from livestock operations. Few data are available on emissions from livestock facilities in the USA and the management practices that may minimize emissions. The objective of this study was to measure seasonal and bedding impacts on ammonia emissions from tie-stall dairy barns located in central Wisconsin. Four chambers each housed four Holstein dairy heifers (approximately 17 mo of age; body weights, 427-522 kg) for three 28-d trial periods corresponding to winter, summer, and fall. A 4x4 Latin Square statistical design was used to evaluate four bedding types (manure solids, chopped newspaper, pine shavings, and chopped wheat straw) in each chamber for a 4-d ammonia monitoring period. Average ammonia-N emissions (g heifer(-1) d(-1)) during summer (20.4) and fall (21.0) were similar and twice the emissions recorded during winter (10.1). Ammonia-N emissions accounted for approximately 4 to 7% of consumed feed N, 4 to 10% of excreted N, and 9 to 20% of manure ammonical N. Cooler nighttime temperatures did not result in lower ammonia emissions than daytime temperatures. Ammonia emissions (g heifer(-1) d(-1)) from chambers that contained manure solids (20.0), newspaper (18.9), and straw (18.9) were similar and significantly greater than emissions using pine shavings (15.2). Chamber N balances, or percent difference between the inputs feed N and bedding N, and the outputs manure N, body weight N, and ammonia N were 105, 90, and 89% for the winter, summer, and fall trials, respectively. Relatively high chamber N balances and favorable comparisons of study data with published values of ammonia emissions, feed N intake, and manure N excretion provided confidence in the accuracy of the study results.     

Nutrient transport from livestock manure applied to pastureland using phosphorus-based management strategies

Land applications of manure from confined animal systems and direct deposit by grazing animals are both major sources of nutrients in streams. The objectives of this study were to determine the effects of P-based manure applications on total suspended solids (TSS) and nutrient losses from dairy manures and poultry litter surface applied to pasturelands and to compare the nutrient losses transported to the edge of the field during overland flow events. Two sets of plots were established: one set for the study of in-field release and another set for the study of edge-of-the-field nutrient transport. Release plots were constructed at three pastureland sites (previous poultry litter applications, previous liquid dairy manure application, and no prior manure application) and received four manure treatments (turkey [Meleagris gallopavo] litter, liquid dairy manure, standard cowpies, and none). Pasture plots with a history of previous manure applications released higher concentrations of TSS and higher percentages of total P (TP) in the particulate form. Transport plots were developed on pasture with no prior manure application. The average flow-weighted TP concentrations were highest in runoff samples from the plots treated with cowpies (1.57 mg L(-1)). Reducing excess P in dairy cow diets and surface applying manure to the land using P-based management practices did not increase N concentrations in runoff. This study found that nutrients are most transportable from cowpies; thus a buffer zone between pastureland and streams or other appropriate management practices are necessary to reduce nutrient losses to waterbodies.     

Assessment of manure phosphorus export through turfgrass sod production in Erath County, Texas

A best management practice (BMP) for exporting manure phosphorus (P) in turfgrass sod from the North Bosque River (NBR) watershed in central Texas was assessed using a geographic information system (GIS). The NBR watershed has a mandate to reduce the total annual P load to the NBR by 50% as a result of total maximum daily load regulation. Since dairy waste applications to fields are identified as the major nonpoint source of P to the river, innovative BMPs, such as export of manure P in turfgrass, will be needed to achieve the 50% reduction. However, methods are needed to evaluate the feasibility of these innovative management practices prior to their implementation. A geospatial database of suitable turfgrass production sites was developed for Erath County using GIS. Erath County largely encompasses the upper portion of the NBR watershed. Information from field experiments, production practices, and ground-truthing was used to search, analyze, and verify a geospatial database developed from national and regional sources. The integration and analyses of large databases supports the search by turf producers for sites suitable for turfgrass sod production in Erath County. In addition, GIS enables researchers and regulators to estimate manure P exports and reduced P loading due to implementation of the manure export BMP on a county scale. Under optimal conditions 198,000 kg manure P yr(-1) could be used and 114,840 kg manure P yr(-1) exported from the NBR watershed through implementation of a system using dairy manure to produce turfgrass sod. This is the equivalent of the manure P applied from 10,032 dairy cows yr(-1) and exported from 5808 dairy cows yr(-1). Application of GIS to large-scale planning and decision-making transcends traditional field-scale applications in precision agriculture.     

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.     

Effect of broadcast manure on runoff phosphorus concentrations over successive rainfall events

Concern over eutrophication has directed attention to manure management effects on phosphorus (P) loss in runoff. This study evaluates the effects of manure application rate and type on runoff P concentrations from two, acidic agricultural soils over successive runoff events. Soils were packed into 100- x 20- x 5-cm runoff boxes and broadcast with three manures (dairy, Bos taurus, layer poultry, Gallus gallus; swine, Sus scrofa) at six rates, from 0 to 150 kg total phosphorus (TP) ha(-1). Simulated rainfall (70 mm h(-1)) was applied until 30 min of runoff was collected 3, 10, and 24 d after manure application. Application rate was related to runoff P (r2 = 0.50-0.98), due to increased concentrations of dissolved reactive phosphorus (DRP) in runoff; as application rate increased, so did the contribution of DRP to runoff TP. Varied concentrations of water-extractable phosphorus (WEP) in manures (2-8 g WEP kg(-1)) resulted in significantly lower DRP concentrations in runoff from dairy manure treatments (0.4-2.2 mg DRP L(-1)) than from poultry (0.3-32.5 mg DRP L(-1)) and swine manure treatments (0.3-22.7 mg DRP L(-1)). Differences in runoff DRP concentrations related to manure type and application rate were diminished by repeated rainfall events, probably as a result of manure P translocation into the soil and removal of applied P by runoff. Differential erosion of broadcast manure caused significant differences in runoff TP concentrations between soils. Results highlight the important, but transient, role of soluble P in manure on runoff P, and point to the interactive effects of management and soils on runoff P losses.     

Antibiotic losses from unprotected manure stockpiles

Manure management is a major concern in livestock production systems. Although historically the primary concerns have been nutrients and pathogens, manure is also a source of emerging contaminants, such as antibiotics, to the environment. There is a growing concern that antibiotics in manure are reaching surface and ground waters and contributing to the development and spread of antibiotic resistance in the environment. One such pathway is through leaching and runoff from manure stockpiles. In this study, we quantified chlortetracycline, monensin, and tylosin losses in runoff from beef manure stockpiles during two separate but consecutive experiments representing different weather conditions (i.e., temperature and precipitation amount and form). Concentrations of chlortetracycline, monensin, and tylosin in runoff were positively correlated with initial concentrations of antibiotics in manure. The highest concentrations of chlortetracycline, monensin, and tylosin in runoff were 210, 3175, and 2544 microg L(-1), respectively. Relative antibiotic losses were primarily a function of water losses. In the experiment that had higher runoff water losses, antibiotic losses ranged from 1.2 to 1.8% of total extractable antibiotics in manure. In the experiment with lower runoff water losses, antibiotic losses varied from 0.2 to 0.6% of the total extractable antibiotics in manure. Manure analysis over time suggests that in situ degradation is an important mechanism for antibiotic losses. Degradation losses during manure stockpiling may exceed cumulative losses from runoff events. Storing manure in protected (i.e., covered) facilities could reduce the risk of aquatic contamination associated with manure stockpiling and other outdoor manure management practices.     

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.     

Influence of data preprocessing on the quantitative determination of nutrient content in poultry manure by near infrared spectroscopy

With increasing concern over potential polltion from farm wastes, there is a need for rapid and robust methods that can analyze livestock manure nutrient content. The near infrared spectroscopy (NIRS) method was used to determine nutrient content in diverse poultry manure samples (n=91). Various standard preprocessing methods (derivatives, multiplicative scatter correction, Savitsky-Golay smoothing, and standard normal variate) were applied to reduce data systemic noise. In addition, a new preprocessing method known as direct orthogonal signal correction (DOSC) was tested. Calibration models for ammonium nitrogen, total potassium, total nitrogen, and total phosphorus were developed with the partial least squares (PLS) method. The results showed that all the preprocessed data improved prediction results compared with the non-preprocessing method. Compared with the other preprocessing methods, the DOSC method gave the best results. The DOSC method achieved moderately successful prediction for ammonium nitrogen, total nitrogen, and total phosphorus. However, all preprocessing methods did not provide reliable prediction for total potassium. This indicates the DOSC method, especially combined with other preprocessing methods, needs further study to allow a more complete predictive analysis of manure nutrient content.     

Response of antibiotics and resistance genes to high-intensity and low-intensity manure management

The purpose of this study was to determine the response of antibiotics and antibiotic resistance genes (ARG) to manure management. A pilot field study was conducted using horse manure containing no antibiotics, into which chlortetracycline (CTC), tylosin (TYL), and monensin (MON) were spiked and compared to unspiked controls. Subsequently, a large-scale field study was conducted comparing manure from a dairy with minimal use of antibiotics and a feedlot with regular subtherapeutic use of antibiotics. The manures were subjected to high-intensity management (HIM) (amending, watering, and turning) and low-intensity management (LIM) (no amending, watering, or turning) and were monitored for antibiotic concentrations and levels of tetracycline ARG [tet(W) and tet(O)] using quantitative real-time polymerase chain reaction. All three antibiotics in the pilot study dissipated more rapidly in HIM manure, with half-lives ranging from 4 to 15 d, compared to LIM manure, with half-lives ranging from 8 to 30 d. Levels of tet(W) were significantly higher after 141 d of treatment, but levels of tet(O) were significantly lower in all treatments. In the large-scale study, the feedlot manure had higher initial concentrations than the dairy manure of tetracycline (TC), oxytetracycline (OTC), and CTC as well as tet(W) and tet(O). Tetracycline and OTC dissipated more rapidly in HIM manure, with half-lives ranging from 6 to 15 d, compared to LIM manure, with half-lives ranging from 7 to 31 d. After 6 mo of treatment, tet(W) and tet(O) decreased significantly in feedlot manure, whereas dairy manure required only 4 mo of treatment for similar results.     

A simple method to predict dissolved phosphorus in runoff from surface-applied manures

Computer models are a rapid, inexpensive way to identify agricultural areas with a high potential for P loss, but most models poorly simulate dissolved P release from surface-applied manures to runoff. We developed a simple approach to predict dissolved P release from manures based on observed trends in laboratory extraction of P in dairy, poultry, and swine manures with water over different water to manure ratios. The approach predicted well dissolved inorganic (R2 = 0.70) and organic (R2 = 0.73) P release from manures and composts for data from leaching experiments with simulated rainfall. However, it predicted poorly (R2 = 0.18) dissolved inorganic P concentrations in runoff from soil boxes where dairy, poultry, and swine manures had been surface-applied and subjected to simulated rainfall. Multiplying predicted runoff P concentrations by the ratio of runoff to rainfall improved the relationship between measured and predicted runoff P concentrations, but runoff P was still overpredicted for dairy and swine manures. We attributed this overprediction to immediate infiltration of dissolved P in the freely draining water of dairy and swine manure slurries upon their application to soils. Further multiplying predicted runoff dissolved inorganic P concentrations by 0.35 for dairy and 0.60 for swine manures resulted in an accurate prediction of dissolved P in runoff (R2 = 0.71). The ability of our relatively simple approach to predict dissolved inorganic P concentrations in runoff from surface-applied manures indicates its potential to improve water quality models, but field testing of the approach is necessary first.     

Establishing a linkage between phosphorus forms in dairy diets, feces, and manures

Effective manure management to efficiently utilize organic wastes without causing environmental degradation requires a clear understanding of the transformation of P forms from diet to manure. Thus, the objective of this study was to establish quantitative relationships between P forms in diets, feces, and manures collected from U.S. Northeastern and Mid-Atlantic commercial dairy farms. Total P in diets ranged from 3.6 to 5.3 g kg(-1) dry matter, while the feces had higher P than diets (5.7-9.5 g kg(-1)) and manures had lower P (2.5-8.9 g kg(-1)) than feces. The farms with total dietary P of 4.8 to 5.3 g P kg(-1) had twofold higher concentrations of phytic acid (1647-2300 mg P kg(-1)) than farms with 3.6 to 4.0 g dietary P kg(-1) (844-1100 mg P kg(-1)). Much of the phytic acid in diets was converted to inorganic orthophosphate in the rumen as indicated by a reduction in phytic acid percentage from diets (32%) to feces (18%). The proportion of orthophosphate diesters (phospholipids, deoxyribonucleic acid [DNA]) was twice as high in feces (6.2-10%) as diets (2.4-5.3%) suggesting the excretion of microbial residues in feces. Phosphonates (aminoethyl phosphonates and phosphonolipids) were not seen in diets but were detected in feces and persisted in manures, which suggests a microbial origin. These organic compounds (phytic acid, phospholipids, DNA) were decomposed on storage of feces in slurry pits, increasing orthophosphate in manures by 9 to 12% of total P. These results suggest that reducing dietary P and typically storing feces in dairy farms will result in manure with similar chemical forms (primarily orthophosphate: 63-77%) that will be land applied. Thus, both the reduction of dietary P and storage of manure on farm are important for controlling solubility and bioavailability of P forms in soils and waters.     

Particulate and dissolved phosphorus chemical separation and phosphorus release from treated dairy manure

In confined animal feeding operations, liquid manure systems present special handling and storage challenges because of the large volume of diluted wastes. Water treatment polymers and mineral phosphorus (P) immobilizing chemicals [AI2(SO4)3 x 18H2O, FeCl3-6H2O, and Class C fly ash] were used to determine particulate and dissolved reactive phosphorus (DRP) reduction mechanisms in high total suspended solid (TSS) dairy manure and the P release from treated manure and amended soils. Co-application exceeded the aggregation level achieved with individual manure amendments and resulted in 80 and 90% reduction in metal salt and polymer rates, respectively. At marginally effective polymer rates between 0.01 and 0.25 g L(-1), maximal aggregation was attained in combination with 1 and 10 g L(-1) of aluminum sulfate (3 and 30 mmol Al3+ L(-1)) and iron chloride (3.7 and 37 mmol Fe3+ L(-1)) in 30 g L(-1) (TSS30) and 100 g L(-1) TSS (TSS100) suspensions, respectively. Fly ash induced particulate destabilization at rates > or = 50 g L(-1) and reduced solution-phase DRP at all rates > or = 1 g L(-1) by 52 and 71% in TSS30 and TSS100 suspensions, respectively. Aluminum and Fe salts also lowered DRP at rates < or = 10 g L(-1) and higher concentrations redispersed particulates and increased DRP due to increased suspension acidity and electrical conductivity. The DRP release from treated manure solids and a Typic Paleudult amended with treated manure was reduced, although the amendments increased Mehlich 3-extractable P. Therefore, the synergism of flocculant types allowed input reduction in aggregation aid chemicals, enhancing particulate and dissolved P separation and immobilization in high TSS liquid manure.