Duration: 10/01/2003 to 09/30/2008

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Project's Primary Website is at http://www.uga.edu/srel/S-1014_Multi-State_Research_Project/index.html(direct link can be found under LINKS)

Establishing a new mutli-state research project focusing on phosphorus (P) dynamics in animal waste amended soils throughout the Southeastern US is justified for several reasons. As the area available for animal waste disposal decreases and livestock production facilities continue the shift to intensive confined management practices, there is an increased potential to degrade both agricultural productivity and general environmental quality. The potential for nitrate leaching to compromise groundwater sources and the detrimental impact of P runoff on surface water quality through eutrophication have been widely recognized and investigated(Sharpley and Moyer, 2000; Sharpley et al., 1994; Wright et al., 1998). However, several issues associated with P cycling in animal waste amended soils and its impact on the partitioning of other contaminants are not being actively addressed by other research initiatives (see Related, Current, and Previous Work below) and, therefore, warrant further investigation.


Application rates for animal wastes were previously based on nitrogen content (N), which means that levels of applied P often exceeded crop utilization(Sharpley et al., 1994). Poultry and swine wastes generally contain higher levels of P due to the lack of enzyme systems that promote efficient digestion and uptake of organic forms of P, along with the practice of adding inorganic P to livestock diets to alleviate any potential deficiency. High soil P loading rates associated with swine and poultry manure often confound routine soil testing procedures(Moore et al., 1998b), and impending regulations require the development of P based application rates for animal wastes that would drastically increase the acreage necessary for waste disposal. In addition, animal wastes may also contain pathogens, hazardous trace elements, toxic organic constituents, and dietary additives, such as Cu, Zn, As, and Se(Wright et al., 1998). In some cases, combining animal wastes with other industrial byproducts, such as coal combustion fly ash, has been suggested as a means of reducing P availability, but may increase the levels of potentially toxic trace metals.


Recent studies have indicated that toxic metals are a much greater health hazard in sludge amended soils than previously recognized(McBride, 1995; McBride, 1998). In a similar manner, trace element contaminants may be released as the organic fraction of the animal waste is mineralized and dissolved organic complexing agents are produced. As in municipal sludge amended soils(McBride and Martinez, 2000; Moore et al., 1998c), waste-derived organics may facilitate the bioavailability and migration of hazardous trace elements through the formation of soluble organic-metal complexes. Furthermore, phytic acid, the primary form of organic P found in poultry and swine manure (i.e., 50-65% in some estimates), forms strong complexes with numerous environmentally relevant metals [e.g., Al, Ca, Fe(II), Fe(III), Pb, Cd, Zn, Sr], the solubility of which can be readily influenced by numerous chemical factors(Seaman et al., 2003a). In addition, orthophosphate, phytic acid, and the P-containing degradation products can act as strong competitors with As, and Se for sorption sites on amphoteric mineral surfaces(Ognalaga et al., 1994; Peryea, 1991).


The empirical nature of soil testing is due in part to the necessity to screen multiple soils reflecting a range of chemical and mineralogical properties(Sims et al., 1998). In recognition of such limitations, a recent review by the USDA recommended additional research concerning the mechanisms of P sorption (i.e., precipitation and adsorption) and long-term stability of such phases in manure-amended soils(Moore et al., 1998b). Greater characterization of mobile P impacting surface water bodies (soluble, particulate mineral, organic, etc.) is also critical in the development of targeted management strategies that focus on a specific P form (Sharpley and Tunney, 2000), such as erosion control to reduce the migration of particulate associated P.


Animal waste disposal is a critical issue facing a number of states and the current the proposal is consistent with research needs identified in a recent USDA review on the subject(Moore et al., 1998b; Wright et al., 1998). Current research efforts largely focus on improving management practices to balance P inputs and outputs at the field and watershed scale (See SERA-IEG17). Such activities have resulted in the development of a multi-parameter system for predicting the risk of surface water degradation due to agricultural P, i.e., the Phosphorus Index (PI) (Lemunyon and Daniel, 1998; Sharpley and Tunney, 2000). Recognizing the importance of erosion and surface runoff in controlling eutrophication, the PI also takes into consideration factors such as topography, cropping system, and infiltration rate, in addition to soil P test values (Beegle et al., 1998; Moore et al., 1998a). As with soil testing for agronomic purposes (i.e., yield response to fertilizer application), the main goal in environmental soil testing is correlating a given laboratory threshold (extractable soil P) with bio-available P, and the release of soil bound P to solution and runoff.


Aside from logistical considerations, the choice of an appropriate extracting agent is largely based on assumptions concerning the reactive phase controlling nutrient partitioning. In moderately weathered, slightly acidic to alkaline soils, P availability is largely assumed to be controlled by the solubility of Ca-PO4 minerals and/or PO4 sorption to soil carbonates, while in more highly weathered acidic soils, such as those found throughout the Southeastern US, the formation of Al- and Fe-PO4 minerals or sorption to Al and Fe oxides is assumed to control availability(Sims et al., 1998). Recent spectroscopic studies, however, have suggested that such assumptions may not be valid in systems with long-term histories of high P loading from inorganic fertilizers or animal manures(Hesterberg et al., 1997; Peak et al., 2002; Pierzynski et al., 1990a; Pierzynski et al., 1990b; Pierzynski et al., 1990c). For example, Pierzynski et al. (Pierzynski et al., 1990a; Pierzynski et al., 1990b; Pierzynski et al., 1990c)found little evidence for the persistence or formation of Ca phosphates in excessively fertilized soils, even in soils with relatively high pH values.


Recent studies have demonstrated that adding Ca, Al or Fe containing compounds to manure before land application reduces P bioavailability, either through adsorption or the formation of insoluble P-containing precipitates(Dao et al., 2001; Moore et al., 1998b; Moore et al., 1998c), with the mechanisms still in some dispute(Peak et al., 2002). Similar reactions likely occur in the soil environment as the large organic pool is mineralized over time, with direct implications to the migration and bioavailability of other waste-derived contaminants. Phosphate minerals, such as apatite can sequester transition and heavy metals, metalloids and radionuclides through adsorption and/or the formation of secondary PO4 precipitates that remain stable over a wide range of geochemical conditions(Cao et al., 2002; Traina and Laperche, 1999; Wright, 1990; Wright et al., 1987). In highly weathered soil systems containing elevated levels of contaminant metals, apatite addition was shown to sequester a number of contaminant metals (i.e., U, Ni, Pb, etc.) during the formation of secondary Al-phosphate precipitates (Arey et al., 1999; Seaman et al., 2001) similar in nature to the poorly ordered Al-phosphates previously identified in excessively fertilized soils(Pierzynski et al., 1990b). In contrast, Peak et al. (2002) recently demonstrated that the reduction in P solubility in poultry litter treated with alum (aluminum sulfate), resulted from adsorption of PO4 and P-containing organics to Al(OH)3, rather than precipitation of Al-phosphates. Secondary phase formation is further complicated by the fact that metals sorbed to mineral oxides can act as precursors for precipitation below the solubility threshold for a given phase(Sato et al., 1997), i.e., surface facilitated precipitation. However, excess phytate can also inhibit further precipitation of inorganic PO4 minerals and the subsequent transformation to more crystalline phases. Such mechanisms, which affect the long-term fate of soil P, cannot be deduced by soil tests, but require a more fundamental understanding of P interactions with soil minerals.


The proposed research project addresses the above concerns by improving our understanding of P dynamics within waste-amended soils, focusing on the interactions of various forms of P with soil mineral components through sorption and/or the formation of secondary P-containing precipitates, and the impact that such processes have on other co-contaminants, such as Cu and Zn in swine manure and As in poultry manure. Although not the focus of the current proposal, the results have clear implications to fertility management and soil testing for waste-amended soils, and will improve our general understanding of contaminant partitioning in PO4 amended soils, an area of great research interest as a means of reducing metal bioavailability in contaminated soils(Cao et al., 2002), a process known as ?in situ immobilization?. Furthermore, the geographic extent of such waste disposal practices and the complexities inherent to soil systems warrant a multi-state research effort that takes advantage of the technical expertise from a number of represented institutions, which should also lead to an improvement in the interpretation of soil test results for environmental purposes and provide defensible recommendations for P management in an agronomic setting.

Related, Current and Previous Work

Information exchange with various research groups will be fostered by the exchange of annual reports and by invitation for participants to join the proposed regional project. An extensive review of current multi-state research and extension projects, generally limited to projects focusing on soil testing and nutrient status, P cycling in the soil environment, and the utilization/disposal of P containing wastes (i.e., poultry and swine manure), indicated little potential for overlap with current proposed activities. A listing of the most relevant projects is provided below:

• SERA-IEG-17: Minimizing Agricultural Phosphorus Run-Off Losses for Protection of Water Resources
  
• S-1006: Insect and Manure Management in Poultry Systems: Elements Relative to Food Safety and Nuisance Issues
  
• S-1000: Animal Manure and Waste Utilization, Treatment and Nuisance Avoidance for a Sustainable Agriculture
  
• SERA-IEG-06: Nutrient Analysis of Soils, Plants, Water, and Waste Materials
  
• W-195: Water Quality Issues in Poultry Production and Processing
  
• W-170: Chemistry and Bioavailability of Waste Constituents in Soils
  
• NCR-013: Soil Testing and Plant Analysis
  
• NEC-067: Soil Testing

(SERA-IEG, Southern Extension/Research Activity-Information Exchange Group; NEC, North Eastern-Information Exchange Group; NCR, North Central Region-Information Exchange Group; S, Southern Region- Multi-state Research Project; W, Western Region-Multi-state Research Project)



The proposed committee activities are unique for several reasons. None of the projects identified in the current survey concentrate on the fate of co-contaminants other than plant macronutrients (i.e., N and K), pathogens, and associated organics/organic matter. Many of these projects focus on P migration at the field and watershed scale due to the dominant role that surface runoff and erosion, as impacted by agronomic management practices, affect surface water eutrophication. Regional projects related to soil testing and plant analysis generally emphasize standardizing laboratory methods/practices within a given region, and developing correlative plant response data to validate fertilizer recommendations. The current project focuses on soils that would generally fall in the ?above optimum? test range for soil P, where typical soil testing methods may be of little agronomic utility.


The Southern Region Extension and Research Activity- Information and Exchange Group 17 (SERA-IEG 17), Minimizing Agricultural Phosphorus Run-Off Losses for Protection of Water Resources, represents the greatest potential for overlap with the proposed activities. SERA-IEG17 is an integrated multi-disciplinary information exchange group focused on further refining ?field-scale assessment tools for P?, as a means of predicting and controlling the role of P in eutrophication. A major goal of this group is the development of application/management strategies that account for the soil conditions and the likelihood of soil runoff when assigning a threshold level above which P may likely affect surface water bodies, with less emphasis on mechanistic soil processes at the solution/mineral interface. Although improved soil testing is a major focus of this group, such activities are generally related to correlating soil test values with the relative sensitivity of surface water resources, rather than evaluating the dynamic interaction of various soil P fractions with other soil contaminants.


The W-170 project, Chemistry and Bioavailability of Waste Constituents in Soils, addresses the long-term bioavailability of trace elements in residues and residue-amended soils for a range of amendment materials, including municipal sludge, fly ash, yard wastes, etc. The primary objective of the committee is to evaluate changes in soil quality as influenced by the land application of such wastes, in order to develop annual and cumulative loading limits for elements currently regulated under EPA 503 (As, Cd, Cu, Cr, Hg, Mo, Ni, Se, Pb, and Zn). Animal waste and P are not major subjects of interest to this group.


Project S-1006, Insect and Manure Management in Poultry Systems: Elements Relative to Food Safety and Nuisance Issues, focuses on issues related to animal mortality, manure litter management, and processing plant waste. Their main goal is the development of management strategies that reduce the nutrient load of such wastes and the presence of nuisance insects and food-borne pathogens that can reside/breed in animal manure, with each participant focusing on livestock management practices common to their geographic region.


SERA-IEG-06, Nutrient Analysis of Soils, Plants, Water, and Waste Materials, serves as an information exchange group for the southeastern region focusing on aspects associated with soil and plant testing, periodically producing a summary of the current soil/plant testing procedures used by each member institution, and noting specific procedure changes that have occurred. Little potential overlap exists with projects focusing mainly on soil testing and fertility as indicated above; however, at least one of the common soil P extractants (Mehlich 1, Mehlich 3, etc.) will be used for comparison in the current study to assist soil testing facilities in developing recommendation criteria for environmental management practices.


As discussed above, the current project seeks to improve our understanding of the processes controlling P partitioning at the mineral/solution interface (i.e., precipitation/sorption reactions), and the influence that such dynamic reactions have on other important co-contaminants, such as As, Cu, and Zn. Therefore, there is only limited potential for overlap and information generated by the current proposed project will be of general utility in developing appropriate ?animal waste and nutrient management? plans necessary to avoid water pollution and generally improve environmental quality.

Objectives

1. Relate soil mineralogical properties to organic and inorganic P speciation, release, and saturation/retention capacity.
   
2. Evaluate the influence of solid phase speciation of P on the partitioning and mobility of trace element contaminants (e.g., As, Se, Cu, and Zn).
   
3. 
   

Methods

The proposed research will rely heavily on the expertise of the committee members. A summary of each participant?s responsibilities as discussed during proposal development is included in the proposal as Table 2. Responsibilities may shift as additional collaborators join the project. An interactive website, maintained by The University of Georgia- Savannah River Ecology Laboratory (SREL), detailing experimental protocols, each participant?s responsibilities and highlighting project accomplishments is currently under development and will be posted prior to the 2003 Agronomy Society Meetings. In general, the website will foster better communication/cooperation within the committee, and serve to inform interested parties with respect to the research progress. The committee will initially include one or more surface soils and or litter/manure samples from each represented state/participant within the project. During the initial phase, all soils/samples will be forwarded to SREL for distribution to the participant institutions. After the initial screening, the committee may choose a limited number of soils for more in depth characterization. In addition to evaluating the impact of freshly applied waste, the current study will utilize existing study plots and/or cultivated fields with relatively well-defined histories of animal waste application. When possible, adjacent areas that have not received P amendments will be included in the study for comparison. Additional soils with elevated levels of P resulting from practices other than manure additions may be included in the study as deemed appropriate. Each study soil will be thoroughly characterized in terms of composition, particle size, clay mineralogy (e.g., x-ray diffraction (XRD), thermal gravimetric analysis (TGA))(Dixon and Weeds, 1989; Whittig and Allardice, 1986), specific surface area(Carter et al., 1986), and chemistry (e.g., pH, cation exchange capacity (CEC), CBD-Fe, organic matter content, etc.) using standardized methods(Jackson, 1979; Jackson et al., 1986). Identification of mineral phases controlling the partitioning of P in the soil environment has generally been confounded by the relatively low P concentration in most soils, and possibly the complex nature and variable composition of P-bearing phases, despite evidence that P resides in discrete particles and not generally sorbed across the entire soil matrix(Pierzynski et al., 1990b). The current focus on soils with high P loading rates should address such experimental limitations. In addition, the study soils will be fractionated based on both particle size and density, as previous studies indicate that PO4-rich phases may be concentrated within the clay fraction and lower density separates (< 2.2 Mg/m3)(Pierzynski et al., 1990b). The separates will be analyzed for total P content and characterized in terms of composition (EDXA), morphology, and crystalline structure (SAED) by analytical electron microscopy (AEM). Fixation and thin sectioning techniques may be used as necessary. Recognizing the importance of soil erosion and runoff major vectors for P migration to surface water bodies, minimally destructive colloid extraction methods, such as water dispersible clay extraction will be used to generate particulate samples for extensive characterization (mineralogy, composition, surface charge, etc.) (Seaman et al., 2003b)by the committee using the methods developed in the current regional project (S280: Mineralogical Controls on Colloid Dispersion and Solid-Phase Speciation of Soil Contaminants). Selective extraction techniques will used to operationally define P reservoirs within the study soils(Miller et al., 1986). Batch procedures will be used to extract soil pore solutions for chemical analysis, including analysis for both soluble organic and inorganic P species, important trace elements (i.e., Cu, Zn, As, etc.), and major soluble inorganic components. Such results will be subjected to equilibrium-based geochemical modeling using the U.S. Environmental Protection Agency?s MINTEQA2 (v. 3.11) or similar modeling codes (e.g., GEOCHEM, PHREEQC2) to identify potential solid phases that may control P and contaminant metal solubility(Pierzynski et al., 1990a). The model database will be updated as necessary to take advantage of recently defined equilibrium constants. Partitioning and release kinetics will also be evaluated as an alternate approach to equilibrium-based studies. Enzymatic extraction schemes will be used in fractionating various forms of organic P in amended soils and animal waste materials(Zyla, 1991). Recent studies have suggested that such operational methods overestimate various forms of organic P because of the non-specific nature of the enzyme and the difficulty in analyzing specifically for phytate and its degradation products. When possible, chromatographic separation techniques under development by members of the committee will be used to quantify specific forms of organic P thought to persist in the soil environment, e.g., phytate(Talamond et al., 2000). Such enzymatic extractions are of renewed interest due to the growing practice of adding phytase to animal feeds to increase P use efficiency, and the concern that such enzymes may degrade organic arsenicals that are commonly used as feed additives, hastening the release of inorganic As and possibly other trace elements within the animal digestive system or the soil environment. Reagent grade organic compounds and PO4 mineral standards will be included in such experiments for comparison. As necessary, selective extraction methods will be used to concentrate the relevant solid fractions for more in-depth study. Extraction data will also be correlated with extractable P levels using one of the more popular soil testing extracts, most likely the Mehlich 3 extract, which is suitable for the analysis of other nutrients by ICP-OES. Such comparative data sets can be used in validating the application of current soil testing methods to environmental management practices. Dr. M. Wilson, an ecological statistician for the University of Georgia that participated in the S280 project, will assist the committee with experimental design and data interpretation as necessary.

Project Task	Investigator
Maintenance of committee website	J. Derrick, UGA Computer Information Specialist II
Sample archiving and distribution	Seaman
Soil characterization	Lynn
Mineralogical characterization, i.e., e., XRD, TGA, CDB/AO extraction etc.	Harris, Hudnall, Karathanasis, Lynn, Smith, Zelazny
Analytical electron microscopy	Seaman, White
Spectroscopic characterization/solid-phase speciation	Hesterberg, Kingery
Solid phase fractionation	Essington, Smith
Batch sorption/extraction techniques	Hesterberg, Kingery, Loeppert, Seaman, others
Equilibrium based modeling	Hesterberg, Kingery, Loeppert, Seaman, others
Statistical analysis	Wilson

Measurement of Progress and Results

Outputs

• Annual project reports highlighting the results for the previous year, which will be made generally available on a website, and forwarded to participants in the related projects identified above.
• As deemed appropriate, participants will submit research findings for publication in peer reviewed journals.
• A final report will be issued at the conclusion of the project.

Outcomes or Projected Impacts

• Improve understanding of processes controlling inorganic and organic P partitioning at the soil mineral interface (i.e., precipitation/sorption reactions).
• Improve understanding of the influence that dynamic reactions at the soil mineral interface have on the mobility and bioavailability of important co-contaminants, such as As, Cu, and Zn.
• Provide additional information to assist in developing appropriate animal waste and nutrient management plans necessary to avoid water pollution and generally improve environmental quality.
• Provide information that will be useful in development of scientifically defensible regulatory guidelines for the disposal and management of P containing wastes, and sites with an extended history of P buildup.

Milestones

(2004): Establish and routinely update project website documenting project objectives and research deliverables for communication to the committee members. Identify appropriate field sites and/or soil and litter/manure samples for subsequent characterization based on total P levels, and common P-containing organics (i.e., phytate). Collect sufficient historical management information for each field site. Assign participants experimental tasks based on his or her expertise and access to appropriate supplies and instrumentation.

(2005): Develop appropriate soil fractionation methods for production of materials for characterization in subsequent phases of the study. Initiate instrumental characterization, such as x-ray diffraction (XRD) and analytical electron microscopy (AEM), of soils and residual solid materials from batch experiments. Develop and implement various batch partitioning/release and extraction experiments.

(2006): Continue batch partitioning/release and extraction experiments. Chemically analyze the resultant extracts for various forms of P and other trace elements. Continue instrumental characterization of soils and residual solid materials from batch experiments.

(2007): Complete batch partitioning/release and extraction experiments. Chemically analyze the resultant extracts for various forms of P and other trace elements. Continue instrumental characterization of soils and residual solid materials from batch experiments.

(2008): Complete instrumental characterization of soils and residual solid materials from batch experiments.

(0):0

Projected Participation

View Appendix E: Participation

Outreach Plan

Results from the proposed committee activities will be published as project reports, a web site, and also as peer-reviewed publications. Participation by committee members involved in undergraduate teaching, graduate student advisement, and extension activities associated with Land Grant Universities will promote the general dissemination of knowledge developed in the proposed project. A summary of the committee activities will be forwarded to the Southern Region Extension and Research Activity- Information and Exchange Group 17 (SERA-IEG 17), Minimizing Agricultural Phosphorus Run-Off Losses for Protection of Water Resources, and posted on the committee website.

Organization/Governance

The core membership in the new multi-state project will likely come from the current S280 Project, Mineralogical Controls on Colloid Dispersion and Solid-Phase Speciation of Soil Contaminants. Preliminary discussions with the current S280 committee have demonstrated considerable support for the proposed area of study. The current S280 officers, which include Dean Hesterberg, Chairman (NC State), John Seaman, Chair Elect (Savannah River Ecology Lab-UGA), and Joey Shaw, Secretary (Auburn), will serve as the initial governing body through their current appointment. Representatives from the member institutions will meet semiannually to assign tasks and review progress on the current research project Additional participants with expertise in soil fertility, microbiology and other related disciplines, including participants in current related projects identified above will be invited to join the committee.

Literature Cited

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Beegle, D., A. Sharpley, and D. Graetz. 1998. Chapter 4: Interpreting soil test phosphorus for environmental purposes, p. 31-40, In J. T. Sims, ed. Soil testing for phosphorus: Environmental uses and implications, Vol. Southern Cooperative Series Bulletin No. 389. USDA-CREES Regional Committee (SERA-IEG17).


Cao, X., L.Q. Ma, M. Chen, S.P. Singh, and W.G. Harris. 2002. Impacts of phosphate amendments on lead bioavailability at a contaminated site. Environ. Sci. Technol. 36:5296-5304.


Carter, D.L., M.M. Mortland, and W.D. Kemper. 1986. Specific Surface, p. 413-423, In A. Klute, ed. Methods of Soil Analysis, Part 1. Physical and Mineralogical Methods. ASA, Madison, WI.


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Dixon, J.B., and S.D. Weeds. 1989. Minerals in the Soil Environment. 2nd ed. Soil Science Society of America, Madison, WI.


Hesterberg, D., D. Sayers, W. Zhou, G.M. Plummer, and W.P. Robarge. 1997. X-ray absorption spectroscopy of lead and zinc speciation in a contaminated groundwater aquifer. Environ. Sci. Technol. 31:2840-2846.


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Jackson, M.L., C.H. Lin, and L.W. Zelazny. 1986. Oxides, hydroxides, and aluminosilicates, p. 101-150, In A. Klute, ed. Methods of soil analysis: Part 1, Physical and mineralogical methods, 2nd ed. American Society of Agronomy, Inc., Madison, WI.


Lemunyon, J., and T.C. Daniel. 1998. Phosphorus management for water quality protection: A national effort, p. 1-4, In J. T. Sims, ed. Soil testing for phosphorus: Environmental uses and implications, Vol. Southern Cooperative Series Bulletin No. 389. USDA-CREES Regional Committee (SERA-IEG17).


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McBride, M.B. 1998. Growing food crops on sludge-amended soils: Problems with the U.S. Environmental Protection Agency method of estimating toxic metal transfer. Environ. Tox. Chem. 17:2274-2281.


McBride, M.B., and C.E. Martinez. 2000. Copper phytotoxicity in a contaminated soil: Remediation tests with adsorptive materials. Environ. Sci. Technol 34:4386-4391.


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Moore, P.A., B.C. Joern, and T.L. Provin. 1998a. Chapter 3: Improvements needed in environmental soil testing for phosphorus, p. 21-29, In J. T. Sims, ed. Soil testing for phosphorus: Environmental uses and implications, Vol. Southern Cooperative Series Bulletin No. 389. USDA-CREES Regional Committee (SERA-IEG17).


Moore, P.A., T.C. Daniel, A.N. Sharpley, and C.W. Wood. 1998b. Chapter 3: Poultry Manure Management, p. 60-77 Agricultural Uses of Municipal, Animal, and Industrial Byrpoducts. USDA-ARS: Conservation Research Report #44.


Moore, P.A., T.C. Daniel, J.T. Gilmour, B.R. Shreve, D.R. Edwards, and B.H. Wood. 1998c. Decreasing metal runoff from poultry litter with aluminum sulfate. J. Environ. Qual. 27:92-99.


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Attachments

Land Grant Participating States/Institutions

FL, GA, KY, LA, MO, MS, NC, NJ, TN, TX, VA

Non Land Grant Participating States/Institutions

Texas Tech University, USDA-NRCS