Soluble Phosphorus Released by Poultry Wastes in ... - PubAg - USDA

Communications in Soil Science and Plant Analysis, 37: 1395-1410,2007 Copyright © Taylor & Francis Group, LLC ISSN 0010-3624 print/1532-2416 online DOl: 10.1080/00103620701376031

Soluble Phosphorus Released by Poultry Wastes in Acidified Aqueous Extracts Armando S. Tasistro Agricultural and Environmental Services Laboratories, Georgia, Athens, Georgia, USA

University of

Miguel L. Cabrera and Yebin B. Zhao Department of Crop and Soil Sciences, University of Georgia, Athens, Georgia, USA

David E. Kissel Agricultural and Environmental Services Laboratories, Georgia, Athens, Georgia, USA

University of

Kang Xia Department of Crop and Soil Sciences, University of Georgia, Athens, Georgia, USA

Dorcas H. Franklin J. Phil Campbell Sr. Natural Resource Conservation Center, USDA-Agricultural Research Service, Watkinsville, Georgia, USA

Abstract: Research has shown that measured water-soluble phosphorus (WSP) from poultry litter might have been less than that released in the field. The effects of acidified extractions on soluble P (SP) concentrations were studied, and a buffer was selected to measure SP at pH 6.0, which is a target value for soil management in Georgia. Soluble P concentrations were extracted from poultry wastes at three pHs: 1) at natural pH, using deionized water (Dlw); 2) after titrating Dl., suspensions with

Received 21 December 2005, Accepted 12 June 2006 Address correspondence to Armando S. Tasistro, Agricultural and Environmental Services Laboratories, University of Georgia, 2400 College Station Road, Athens, Georgia 30602-9105, USA. E-mail: [email protected] 1395

1396

A. S. Tasistro

et al.

0.5N hydrochloric acid (HCl) to pH end-points 3.0, 4.0, and 6.0; and 3) at pH 6.0 with buffers of sodium (Na) acetate, potassium hydrogen phthalate (KHP), 2-(Nmorpholino) ethanesulphonic acid (MES), Na cacodylate, imidazole, N-(2-acetamido)-2-aminoethansulphonic acid (ACES), N-(carbamoyl-methyl) iminodiacetic acid (ADA), bis-(2-hydroxyethyl) imino]-tris-[(hydroxymethyl) methane (Bistris), and 1,4 piperazine-bis-(ethane sulphonic acid) (PIPES). Total SP increased 60% to 140% in suspensions acidified with HCl to pH 6.0 compared to suspensions at pH ::::8. Dissolved unreactive P responded more (2x to 30x) than molybdate reactive P(20-100%). Buffers extracted more soluble minerals than suspensions acidified with HCl, probably because of their complexation ability. The most effective buffer was MES, because its effects seemed mainly due to acidification. Keywords: Buffers, dissolved unreactive P, molybdate reactive P, pH, poultry wastes, water-soluble P

INTRODUCTION Large phosphorus (P) concentrations in animal manures, especially watersoluble P (WSP), may lead to environmental deterioration through the contamination of underground or surface water bodies (Carpenter et al. 1998; Kleinman and Sharpley 2003). Simulation models have been used to predict P losses from surface-applied manures (Pierson et al. 2001; Vadas, Kleinman, and Sharpley 2004; Gerard-Marchant, Walter, and Steenhuis 2005; Vadas, Haggard, and Gburek 2005) using input data of WSP in poultry manure extracts that have been traditionally obtained by shaking suspensions of manure in deionized water (DIw) (Self-Davis and Moore 2000). The pH of a suspension of poultry manure in DIw is generally alkaline mainly because of the presence of ammonia (NH3) (Griffiths 2004). In previous research (Tasistro, Cabrera, and Kissel 2004), it was determined that 1 month after applying broiler litter to pastures in northeast Georgia, the pH of treated thatch had decreased from 8.1 to 6.7, which did not differ from the pH of the control. Although 15 days after broiler litter application, the pH of the top 1 em of soil had increased significantly in comparison to the untreated soil, 1 month after the application, the pH of the treated and untreated top 1 em of soil did not differ significantly. Thus, the alkaline effects of broiler litter on thatch and the top 1 em of soil essentially had disappeared 1 month after application. In the same work, evidence was found that the WSP measured at the original litter pH might have been considerably less than that released in the field. The changes in the amount of labile P induced by acidification of litter in thatch and the top 1 em of soil are not considered in the calculations by simulation models. For instance, in the erosion productivity impact calculator (EPIC) simulation model, when organic fertilizer was added, a certain proportion of the P is added to the fresh organic P pool and the remaining

Soluble P Released by Poultry Wastes

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P is added to the labile inorganic P pool (Pierson et al. 2001) without considering the changes in the availability of both the inorganic and organic fractions as a consequence of the decrease in pH that occurs in the first month following application. The solubility of inorganic and organic phosphates tends to increase in acidic conditions (Stumm and Morgan 1981; Champagne 1988). Because of the decrease in pH of poultry litter following its application, soluble P would be measured more accurately, and this value would be a more correct input to simulation models, if the extraction were done at a pH representative of the environment from where runoff is most likely to occur. The objective of this research was to study the effects of acidification on the amounts of soluble P that can be extracted from poultry wastes. Additionally, it was hypothesized that poultry waste might possess a buffer capacity that would prevent attaining stable pH values, a suitable pH buffer that could allow extractions at a predefined pH needed to be identified. The buffer system should have minimum or no influence on the sample being extracted other than to adjust the pH.

MATERIALS AND METHODS Two layer manure and four broiler litter samples with a wide range of total P concentrations were selected from commercial samples submitted for analysis to the University of Georgia Agricultural and Environmental Services Laboratories. The compositions of the litter and manure samples used are shown in Table 1. Soluble P was extracted using three different kinds of extractants. The first extractant was DIw, which would have extracted soluble P at the natural pH of the manures. The second set of extractions was done in acidified DIw suspensions that were prepared by titrating them with 0.5 N hydrochloric acid (HCl) to end pH values of 3.0, 4.0, or 6.0 to study the effect of acidification on soluble P concentrations. The third kind of extractant comprised 0.1 M solutions of the following buffers adjusted to pH 6.0: sodium (Na) acetate, potassium hydrogen phthalate (KHP), 2-(N-morpholino) ethanesulphonic acid (MES), Na cacodylate, imidazole, N-(2-acetarnido)-2aminoethansulphonic acid (ACES), N-(carbamoyl-methyl) iminodiacetic acid (ADA), bis-(2-hydroxyetheyl) imino]-tris-[(hydroxymethyl) methane (Bistris), and 1,4 piperazine-bis-(ethane sulphonic acid) (PIPES). A pH of 6.0 was selected because in previous research (Tasistro, Cabrera, and Kissel 2004) a pH of 6.0 was found to be dominant in samples of thatch and the top 1.0 ern of soil of pastures and because it is a target value when dealing with soil pH management of most agronomic crops in Georgia. Extractions were done in two sets: One set involved broiler litter sample 55 and Na acetate, KHP, MES, Na cacodylate, and imidazole, and all extractions, including those using plain DIw, and acidified DIw, were made in triplicate. The other set included the remaining manure samples and MES, Na

A. S. Tasistro et al.

1398 Table 1. samples

Water and nutrient content of four broiler litter and two layer manure Layer manure samples

Broiler litter samples Property Water (g kg-I) N(gkg-l) P (mgkg-l) K (mg kg-I) Ca(mgkg-l) Mg (mg kg-I) S (mgkg-l) Na (mgkg-l) Fe (mg kg-I) Al (mg kg ")

Mn (mgkg-l) Cu (mg kg-I) Zn (mgkg-l) B (mgkg-l)

55

157

294

339

30

709

280 44.6 18,861 33,228 28,978 6,761 7,289 11,361 1,440 1,210 531 1,092 440 60

168 41.0

92 42.2 14,859 23,907 19,181 5,154 5,163 7,330 1,508 1,435 480 650 313 43

133 18.7 5,513 13,430 8,272 2,394 2,549 4,138 1,797 3,256 216 389 155 28

77 11.7

160 28.6 37,276 41,605 147,952 9,414 7,957 7,052 3,920 4,356 627 99 743 65

34,346 31,322 52,356 11,197 8,053 10,135 14,000 18,702 1,060 1,548 831 30

7,965 10,639 14,761 2,717 2,236 2,761 12,919 34,553 255 59 205 66

Note. All results, except water, are expressed on a dry basis.

cacodylate, ACES, ADA, Bistris, and PIPES. Extractions in this set, including MES, plain DIw, and acidified DIw, were replicated four times, whereas those with the remaining buffers were duplicated. Prior to analysis, each waste sample was homogenized in a blender and subsequently ground to pass through a 0.5-mm screen. Total nitrogen (N) was determined after dry combustion of 0.5 g samples at 1,350°C in a LECO CNS-2000 analyzer, whereas the total concentrations of P, potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), Na, iron (Fe), aluminum (AI), manganese (Mn), copper (Cu), zinc (Zn), and boron (B) were measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES) after microwave enhanced digestion in concentrated nitric acid (HN03) following US-EPA method 3051 (Walter, Chalk, and Kingston, 1997). Water content was determined after oven drying at 65°C for 48 h. In all of the extractions the waste-extractant ratio was 1:200 (0.2 g:40 mL), and suspensions were shaken for 4 h in a reciprocating shaker at 120 oscillations per minute. The pH was measured at 22 to 23°C before and after shaking using a glass electrode. After shaking, the suspensions were centrifuged at 2800 rpm for 20 min, filtered through 0.45-j.Lm filters, and acidified with concentrated HCl to prevent precipitation of calcium phosphates (Self-Davis and Moore 2000). Total dissolved P (TDP), whose concentration was measured by ICP-AES, included inorganic and organic forms. Inorganic P was determined


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colorimetric ally by the molybdenum-blue method (Murphy and Riley 1962) as molybdate reactive P (MRP). The difference between TDP and MRP is referred to as dissolved unreactive phosphorus (DUP) and has been linked mostly to organic P in poultry manure (Withers, Clay, and Breeze 2001). Principal component PC analysis was performed using the Princomp procedure (SAS Institute 1999). An important criterion in the selection of the pH buffer was that its only effect was to lower the pH without complexing cations that were present in insoluble P compounds. To determine if a buffer's effects on soluble P concentrations did not differ significantly from those caused by the acidification of extracting suspensions by 0.5N HCl, 95% confidence intervals (CI) were built in the range of pH values attained by buffers for the regression lines between MRP and DUP concentrations and titration end-point pH.

RESULTS The pH of the suspensions acidified with HCl increased after 4 h of shaking depending on the contrasting pH buffering capacities of the poultry wastes. The 95% CI for mean pH after shaking were 3.05 to 3.73 for pH end-point 3.0, 4.62 to 5.69 for pH end-point 4.0, and 6.46 to 7.10 for pH end-point 6.0. The pH after shaking was considered as extraction pH. The 95% CI for mean pH after shaking across buffers and poultry manures was 5.84 to 6.02, which showed that the suspension pH was effectively maintained around the target value of 6.0. Extractions in acidified conditions resulted in increases in MRP and DUP concentrations, compared to when Dl., was used, that varied among poultry wastes (Figures 1-3). In Figures 1-3, soluble P concentrations from the extractions using natural Dl., were plotted jointly with those from the extractions using Dl., acidified with 0.5 N HCl and correspond to the highest pH values. DUP showed greater responses than MRP to acidification with HCl, which suggests that organic P is more easily influenced by changes in extracting pH. In comparison to extraction at the natural pH of the manures using only Dlw, extraction at pH 6.0 in suspensions acidified with HCl increased MRP concentrations approximately 20% in low-P and medium-P broiler litters and 100% in the high-P layer manure, whereas the response of DUP concentrations ranged from 100% increase in sample 55 (medium-P broiler litter) to a 30-fold increase in sample 339 (low-P broiler litter). In terms of TDP concentrations, lowering the extraction pH to 6.0 with HCl resulted in increments that ranged from 60% to 140% compared to extractions at natural manure pH. MRP and DUP concentrations in all extracts obtained with ADA were consistently greater than the upper limit of the 95% CI for the response of both soluble P forms to titration to pH 6.0 (Figures 1-3). For sample 55, KHP extracted significantly more DUP than what was extracted in suspensions acidified with HCl at pH 6.0 Bistris and PIPES showed a high

A. S. Tasistro et aI.

1400 4500 4000

Layer Low-P

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4000 2000 0 2

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Figure 2.

Molybdate reactive P (MRP) and dissolved reactive P (DUP) extracted from medium-P broiler litter (samples 294 and 55) after titration with 0.5 N HCI or using MES, ACES, ADA, Bistris, and PIPES buffers (sample 294) and cacodylate, KHP, acetate and imidazole buffers (sample 55). Dashed lines indicate the 95% confidence interval for the regression line between soluble P forms extracted after titration and pH. Data points for the highest pH (i.e., the natural pH of the poultry wastes) correspond to extractions using natural deionized water.

Ca, Mg, Mn, Zn, Fe, AI, Cu, and B, meaning that those concentrations increased as pH decreased. With the exception of sample 55 (medium-P broiler litter), the second PC showed that as pH decreased those samples with greater concentrations of MRP, soluble Ca, Mg, and Mn exhibited lower soluble Fe, AI, Cu, and B concentrations and vice versa. Figure 4 shows the plots with the scatter of the extracts from the poultry waste samples against the two first PCs. The response of DUP was not consistent because in the two high-P samples (157 and 709) and the low-P layer sample (30), it behaved like soluble Fe, AI, Cu, and B concentrations, whereas in the remainder of the samples it was positively associated with MRP, soluble Ca, Mg, and Mn (Table 3 and Figure 4). Extracts obtained with ADA, and to a lesser extent with Bistris, PIPES, and ACES, were associated with higher concentrations of soluble' Fe, AI, Cu, and B. For sample 55,


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1405

elements under acidic conditions, which is due to the reduction in affinity between the phosphate groups and cations and to the greater solubility of the metal species in acid conditions (Jackman and Black 1951; Stumm and Morgan 1981; Champagne 1988; Maenz et al. 1999). The relationship between MRP concentrations and soluble Ca and Mg concentrations detected through the PC analysis seems to confirm the importance of Ca and Mg phosphates as sources of soluble P in poultry wastes (Cooperband and Good 2002). There is not a clear explanation for the positive association between soluble B concentrations and those of DUP and soluble Fe, AI, and Cu. If most of the B is present as borate, it can be speculated that the association with DUP concentrations could be related to the ability of borate to complex with sugar phosphates such as phytic acid (Trevelyan 1967; Angyal, Greeves, and Pickles 1974). Additionally, the high stability constants of the Cu- and Fe-borate complexes (Table 4) suggest that those complexes may have formed. The inconsistency in the associations between DUP concentrations and those of MRP and other soluble cations revealed by the PC analysis may be explained by the interactions among pH, buffer compounds, and the varied concentrations of cations and phosphate forms (Champagne 1988). The results showed that those buffers (ADA, KHP, and to a lesser extent Bistris, PIPES, and ACES) that tended to extract more soluble P and were linked to higher concentrations of soluble Fe, AI, Cu, and B also have greater stability constants for metal-buffer complex formation (Table 4). Buffers ADA, Pipes, MES, and ACES belong to a group of zwitterionic buffers derived from N-substituted aminosulfonic acids developed by Good et al. (1966) that reportedly had several advantageous characteristics, among which were their low affinities for metal ions. However, since their original introduction, there have been increasing reports of interferences arising from the use of Good's buffers, which have been ascribed to metal ion complexation (Nakon and Krishnamoorthy 1983). The greater amounts of soluble P extracted in our study by the ADA buffer, and the association between ADA and high soluble Cu, Fe, AI, and B concentrations observed in the PC analysis, seem to confirm the findings by Nakon and Krishnamoorthy (1983) on metal complexing by ADA, especially the very stable ADA-Cu chelate. The affinity of PIPES to complex metals such as Cu, Mn, Zn, Ca, and Mg in solution has been reported by Azab, Orabi, and El-Salam (2001), but the stability constants of complex formation with metals are not as large as those of Bistris or ADA (Table 4). Despite this fact, PIPES tended to be associated with higher soluble P, Cu, Fe, AI, and B concentrations than MES or ACES (Figure 4), which could be explained by the variability in mineral composition among poultry manures. Routinely used buffers other than those developed by Good et al. (1966) have also been shown to complex metal ions, and our results agree with what other authors have found. KHP chelates Cu strongly and Ca less strongly (Chiari, Dell'Orto, and Casella 1996) and has been shown to strongly

Table 4.

Logarithms of stability constants of complexes between seven cations and nine ligands Cations

Ligands

Ca+2

Mg+2

Mn+2

Zn+2

MES ACES

0.7a OAa Negligiblea 4.0a 2A5d 0.55d 2.25e -0.171 1.0d

0.8a OAa Negligiblea 2.5a 2.52d

0.7a 3.85b Negligiblea 4.9a 2.74d 0.80d

3.85b 3A2c 7.1d 2.91d 1.07d

PIPES ADA

KHP Acetate Bistris Imidazole Boric acid

aGood et al. 1966. Anwar and Azab 2000. Azab, Orabi, and El-Salam 2001. dSmith and Martell 2004. "Scheller et al. 1980. IKapinos, Song, and Sigel 1998. b

c

0.51d 0.34e

o.HI 0.8d

0.7' 1At"

2.38e

z.ss'

3.32d

Cu+2 Negligible" 4.6a 3.75c 9.7a 4.02d 1.79d 5.27e 4.311 6.13d


1407

complex other heavy metals (Singh et al. 1980). The buffer Bistris has been shown by Scheller et al. (1980) to complex metals such as Ca, Cu, and Zn even in mixed-ligand systems, and the same authors recommended that reservations should be exercised in employing Bistris as a buffer in systems containing metal ions. Complex formation between imidazole and Zn has been documented by Cini et al. (1997) and between acetate and Fe and Al by Marcos, Buurman, and Meijer (1998) and Earl, Syers, and McLaughlin (1979). Therefore, the results suggest that two processes seem to be taking place. On the one hand, buffers increase DUP and MRP concentrations by lowering pH to around 6.0 (process 1).

Process 1 Me - inorganic phosphate

+ nH+ ±:::tMe+n + H, -inorganic

phosphate (MRP) Me - organic phosphate

+ nH+±:::tMe+n + H, -organic

phosphate (DUP)

where Me = Ca, Mg, K, Cu, Zn, Mn, Fe, and AI. The weakened metal-phosphate bonds and the increased concentration of metals in solution create favorable conditions for their complexation by buffer compounds (process 2).

Process 2 Me+n

+ Buffer-m±:::tMe

- buffer-(m-n)

Additionally, by decreasing the concentrations of free metals in solution, process 2 displaces the equilibrium of metal-inorganic phosphates and metal-organic phosphates dissolution (process 1) to the right, which promotes further dissolution, and leads to greater MRP and DUP concentrations in solution than could be expected from only acidification. Buffers MES and ACES showed the least evidence of increased soluble P concentrations by competitive chelation. However, the PC analysis showed that ACES tended to be associated with increased Cu, Fe, AI, and B concentrations in more cases than MES (Figure 4). This finding agrees with that of Anwar and Azab (2000), who expressed great reservations when employing ACES in aqueous solutions in systems containing Cu, Mn, Zn, Ca, or Mg. Under the conditions of this study, MES appears to be a better choice, which agrees with results obtained elsewhere that have shown it to have a low tendency to complex metals (Balikungeri 1989). Soares et al. (1999) showed that MES does not complex Cd or Pb, whereas Cervini-Silva (2004) selected MES as pH buffer in a study of the interaction between goethite

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and organic ligands because it displayed weak metal complexation in water and little electrochemical activity under environmentally relevant conditions (5.5 < pH < 6.7), because the tertiary amine N is sterically hindered to complex a Lewis acid other than H and by the weak nucleophilicity of MES sulfonic groups.

CONCLUSIONS Soluble P concentrations from acidified suspensions of poultry manures in DIw were considerably higher than from suspensions using only DIw. The soluble organic P fraction showed greater increases than the soluble inorganic P fraction when extracted after acidification. The magnitude of the responses in soluble P concentrations to acid extraction varied with the composition of the poultry waste samples. The increments in soluble P concentrations in excess of what could be expected from lowering pH that was observed with buffers, especially ADA, Bistris, and KHP, were probably due to their high ability to compete with phosphates for metals. The tendency to complex metals by buffer compounds such as imidazole, acetate, PIPES, and ACES was evidenced especially by their association with greater soluble Cu, Fe, AI, and B concentrations shown in the PC analysis. MES showed minimal metal complexation, making it the best buffer compound tested.

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Singh, R.KP., Sircar, J.K, Khelawan, R., and Yadava, KL. (1980) Stability constants of phthalate complexes of copper(II), nickel(II), zinc(II), cobalt(II), uranyl(II) and thorium(IV) by paper electrophoresis. Chromatographia, 13 (11): 709-711. Smith, R.M. and Martell, AE. (2004) NIST Standard Reference Database 46, Version 8.0 for Windows; U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology, Gaithersburg, MD. Soares, H.M.V.M., Conde, P.C.F.L., Almeida, AA.N., and Vasconcelos, M.T. (1999) Evaluation of n-substituted aminosulfonic acid pH buffers with a morpholinic ring for cadmium and lead speciation studies by electroanalytical techniques. Anal. Chim. Acta, 394: 325-335. Stumm, W. and Morgan, J.J. (1981) Aquatic Chemistry, an Introduction Emphasizing Chemical Equilibria in Natural Waters; John Wiley & Sons; New York. Tasistro, A, Cabrera, M.L., and Kissel, D.E. (2004) Water soluble phosphorus released by poultry litter: Effect of extraction pH and time after application. Nutr. Cye!. Agroecosys., 68: 223-234. Trevelyan, W.E. (1967) Removal of the sphingolipid impurity from preparations of yeast phosphatidyl inositol. J. Lipid Res., 8: 281-282. Vadas, P.A., Kleinman, P.J.A, and Sharpley, AN. (2004) A simple method to predict dissolved phosphorus in runoff from surface-applied manures. J. Environ. Qual., 33: 749-756. Vadas, P.A., Haggard, B.E., and Gburek, W.J. (2005) Predicting dissolved phosphorus in runoff from manured field plots. J. Environ. Qual., 34: 1347 -1353. Walter, P.J., Chalk, S., and Kingston, H.M. (1997) Overview of microwave-assisted sample preparation. In Microwave-enhanced chemistry: Fundamentals, Sample Preparation a~d Applications; Kingston, H.M. and Haswell, S.J. (eds.); American Chemical Society: Washington, D.C., 55-222. Withers, P.J.A, Clay, S.D., and Breeze, V.G. (2001) Phosphorus transfer in runoff following application of fertilizer, manure, and sewage sludge. J. Environ. Qual., 30: 180-188.