Phosphorus speciation in broiler litter and turkey manure produced from modified diets

Phosphorus speciation in manure and fertilizer impacted Mid-Atlantic coastal plain soils

Historical applications of manures and fertilizers at rates exceeding crop P removal in the Mid-Atlantic region (United States) have resulted in decades of increased water quality degradation from P losses in agricultural runoff. As such, many growers in this region face restrictions on future P applications. An improved understanding of the fate, transformations, and availability of P is needed to manage P-enriched soils. We paired chemical extractions (i.e., Mehlich-3, water extractable P, and chemical fractionation) with nondestructive methods (i.e., x-ray absorption near edge structure [XANES] spectroscopy and x-ray fluorescence [XRF]) to investigate P dynamics in eight P-enriched Mid-Atlantic soils with various management histories. Chemical fractionation and XRF data were used to support XANES linear combination fits, allowing for identification of various Al, Ca, and Fe phosphates and P sorbed phases in soils amended with fertilizer, poultry litter, or dairy manure. Management history and P speciation were used to make qualitative comparisons between the eight legacy P soils; we also speculate about how P speciation may affect future management of these soils with and without additional P applications. With continued P applications, we expect an increase in semicrystalline Al and Fe-P, P sorbed to Al (hydro)oxides, and insoluble Ca-P species in these soils for all P sources. Under drawdown scenarios, we expect plant P uptake first from semicrystalline Al and Fe phosphates followed by P sorbed phases. Our results can help guide management decisions on coastal plain soils with a history of P application.

Effects of pyrolysis and incineration on the phosphorus fertiliser potential of bio-waste- and plant-based materials

Land application of biomass materials and their products of thermal treatment (biochars and ashes) can offset the unsustainable use of soluble P fertilisers. However, few evaluations of P fertiliser potential have systematically addressed diverse biomass types with contrasting P contents. This paper evaluates the relative P fertiliser potential of four P-rich biowastes (animal bone, poultry manure, pig slurry, and a municipal sewage sludge) and three low-P, plant-based materials (reeds [Phragmites australis L.], rice husks [Oryza sativa L.] and cocoa prunings [Theobroma cacao L.]) and their biochars and ashes. We utilised three complementary approaches: P extractability in single solvents (2% formic and citric acids, and 1 M neutral ammonium citrate); sequential chemical P fractionation, and P dissolution/desorption kinetics. In most cases, pyrolysis and incineration of the P-rich biowastes increased P extractability (% TP) in the single solvents, whilst decreasing water-soluble P. For pig slurry, for example, pyrolysis reduced water-soluble P 20-fold, with corresponding increases observed not only in the solvent-extractable P but also in the pool of potentially plant available, NaHCO3-Pi fraction (e.g., 17 to 35% TP). These complementary datasets were also evident for the low-P feedstocks and thermal products; e.g., pyrolysis increased the NaHCO3-Pi fraction in reed feedstock from 6 to 15% TP. For all biomass feedstocks, biochars and ashes, pseudo-second order P-release kinetics provided the best fit with the experimental data. The data demonstrate scope for using pyrolysis to upgrade the P fertiliser value of a wide range of biomass materials whilst reducing their environmental impact.

Unexpected Cu and Zn speciation patterns in the broiler feed-animal-excreta system revealed by XAS spectroscopy

Trace minerals such as copper (Cu) and zinc (Zn) are animal nutrition supplements necessary for livestock health and breeding performance, yet they also have environmental impacts via animal excretion. Here we investigated changes in Cu and Zn speciation from the feed additive to the broiler excreta stages. The aim of this study was to assess whether different Cu and Zn feed additives induce different Cu and Zn speciation patterns, and to determine the extent to which this speciation is preserved throughout the feed-animal-excreta system. Synchrotron-based X-ray absorption spectroscopy (XAS) was used for this investigation. The principal findings were: (i) in feed, Cu and Zn speciation changed rapidly from the feed additive signature (Cu and Zn oxides or Cu and Zn sulfates) to Cu and Zn organic complexes (Cu phytate and Zn phytate). (ii) in the digestive tract, we showed that Cu and Zn phytate were major Cu and Zn species; Cu sulfide and Zn amorphous phosphate species were detected but remained minor species. (iii) in fresh excreta, Cu sulfide and Zn amorphous phosphate were major species. These results should help to: (i) enhance the design of future research studies comparing different feed additive performances; (ii) assess Cu and Zn bioavailability in the digestive tract; (iii) gain further insight into the fate of Cu and Zn in cultivated soils when poultry manure is used as fertilizer.

Effectiveness of flue gas desulfurization gypsum in reducing phosphorus solubility in poultry litter when applied as an in-house amendment

Phosphorus (P) runoff from agricultural lands receiving poultry litter (PL) poses a major environmental challenge. Application of flue-gas-desulfurization (FGD)-gypsum produced from coal power plants in agricultural lands has shown promise to reduce P losses. However, no information is available about the effectiveness of FGD-gypsum addition in reducing P solubility when applied as an in-house amendment. Hence, the objectives of this study were to understand a) effectiveness of FGD-gypsum as a litter amendment in reducing P loss risk; and b) how FGD-gypsum amendment in PL alters the distribution of P forms. Broiler chickens were raised for five flocks in seven individual litter treatments replicated four times in a randomized complete block design. Based on the FGD-gypsum addition, the PL treatments were broadly classified as FGD-gypsum treated and untreated. Toxic metal concentrations were analyzed in FGD-gypsum as well as the treatments. Sequential water extractions were performed to understand P solubility. Litter P fractionation was performed to identify bioavailable P (Water-P), labile P (NaHCO3-P), aluminum/iron chemisorbed P (NaOH-P), and mineral occluded P (HCl-P). Results indicated significantly higher soluble P in all untreated than in all FGD-gypsum treated litters in the initial water extraction. The FGD-gypsum treated litters reduced soluble P by 58 to 67% in the 1st water extraction compared to untreated litters. Fractionation study revealed lower proportion of Water-P and higher proportion of NaHCO3-P and HCl-P in all FGD-gypsum treated than in untreated litters. This study suggests reuse of FGD-gypsum in broiler houses can help reduce P mobility without any toxic metals concerns.

Nutrient challenges with solid-phase anaerobic digestate as a peat substitute - Storage decreased ammonium toxicity but increased phosphorus availability

The solid fraction (SD) obtained after liquid - solid separation of anaerobic digestate is interesting as a potential fertilizer as well as a peat substitute in horticultural growing substrates. We investigated the effect of incubation of the SD obtained by screw-press separation of digestate produced from food waste and plant residues on potentially plant available mineral nutrients and plant growth. The NH₄-N concentration was initially > 1000 mg L^-1 but rapidly decreased, probably due to NH₃ emission promoted by a high initial pH. No nitrate was detected during the first four weeks of incubation. The concentrations of potentially available P and Mg were closely related and strongly increased during incubation. The effect of adding 20 or 30 vol% of SD to a peat-based growing substrate on the growth of basil and lettuce was investigated before and after the incubation period. With the unincubated SD, the initial substrate NH₄-N of 200-300 mg L^-1 was potentially phytotoxic. Plant growth response ranged from inhibition to stimulation, probably reflecting variation in substrate ammonium status. After 96 days of incubation, ammonium concentrations had decreased with > 50% and basil growth was generally positively affected by addition of incubated SD. However, available P concentrations of 140-210 mg L^-1 in the incubated substrates posed a high risk of P leakage. In conclusion, storage greatly reduced NH₄-N concentrations and phytotoxicity when the SD was used as a partial substituent for peat in a horticultural growing substrate. Measures are needed, however, to limit available P concentrations in high-P solid digestate fractions.

X-ray absorption near edge structure spectroscopy reveals phosphate minerals at surface and agronomic sampling depths in agricultural Ultisols saturated with legacy phosphorus

Legacy phosphorus (P) soils have received excessive P inputs from historic manure and fertilizer applications and present unique management challenges for protecting water quality as soil P saturation leads to increased soluble P to waterways. We used P K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify and quantify the dominant P minerals in four representative legacy P soils under conventional till and no-till management in Maryland, USA. Various measures of extractable soil P, including water-extractable P (20.6-54.1 mg kg^-1 at 1:10 soil-to-water ratio; 52.7-132.2 mg kg^-1 at 1:100 soil-to-water ratio), plant available P extracted with Mehlich 3 (692-1139 mg kg^-1), and Mehlich 3P saturation ratio (0.54-1.37), were above the environmental threshold values, suggesting the accumulation of legacy P in soils. The quantification of dominant P minerals may provide insights into the potential of legacy P soils to contribute to P release for crop use and soluble P losses. Linear combination fits of XANES spectra identified the presence of four phosphate mineral groups, consisting of (i) calcium-phosphate minerals (11-59%) in the form of fluorapatite, β-tricalcium phosphate, and brushite, followed by (ii) iron-phosphate minerals (12-49%) in the form of ludlamite, heterosite, P sorbed to ferrihydrite, and amorphous iron phosphates, (iii) aluminum-phosphate minerals (15-33%) in the form of wavellite and P sorbed to aluminum hydroxide, and (iv) other phosphate minerals (5-35%) in the form of copper-phosphate (cornetite, 5-18%) and manganese-phosphate (hureaulite, 25-35%). Organic P consisting of phytic acid was found in most soils (13-24%) and was more pronounced in the surface layer of no-till (21-24%) than in tilled (16%) fields. Of the P forms identified with XANES, we conclude that P sorbed to Fe and Al, and Ca-P in the form of brushite and β-tricalcium phosphate will likely readily contribute to the soil WEP pool as the soil solution P is depleted by crop uptake and lost via runoff and leaching.

Considering inorganic P binding in bio-based products improves prediction of their P fertiliser value

Prediction of the relative phosphorus (P) fertiliser value of bio-based fertiliser products is agronomically important, but previous attempts to develop prediction models have often failed due to the high chemical complexity of bio-based fertilisers and the limited number of products included in analyses. In this study, regression models for prediction were developed using independently produced data from 10 different studies on crop growth responses to P applied with bio-based fertiliser products, resulting in a dataset with 69 products. The 69 fertiliser products were organised into four sub-groups, based on the inorganic P compounds most likely to be present in each product. Within each product group, multiple regression was conducted using mineral fertiliser equivalents (MFE) as response variable and three potential explanatory variables derived from chemical analysis, all reflecting inorganic P binding in the fertiliser products: i) NaHCO₃-soluble P, ii) molar ratio of calcium (Ca):P and iii) molar ratio of aluminium + iron (Al + Fe):P. The best regression model fit was achieved for sewage sludges with Al-/Fe-bound P (n = 20; R² = 79.2%), followed by sewage sludges with Ca-bound P (n = 11; R² = 71.1%); fertiliser products with Ca-bound P (n = 29; R² = 58.2%); and thermally treated sewage sludge products (n = 9; R² = 44.9%). Even though external factors influencing P fertiliser values (e.g. fertiliser shape, application form, soil characteristics) differed between the underlying studies and were not considered, the suggested prediction models provide potential for more efficient P recycling in practice.

Systematic Study of Legacy Phosphorus (P) Desorption Mechanisms in High-P Agricultural Soils

Repeated manure additions containing phosphorus (P) in excess of crop needs have led to many agricultural soils with high levels of soil P (i.e., legacy P), particularly in the Delmarva region (USA). Due to the potential for P release, it is important to gain a better understanding of the mechanisms of P desorption and solubilization. Agricultural soils with high legacy P were collected from the Delmarva Peninsula, and soil P pools were determined using a suite of wet chemical and spectroscopic techniques, including a modified Hedley sequential extraction and X-ray absorption near-edge structure (XANES) spectroscopy. Five different desorption solutions were used to investigate P removal efficiency to assess release mechanisms. The results indicate that sulfate can have a stronger competition for P desorption than silicate, especially in the ditch sample with 21% labile P and 44% P adsorbed to iron and aluminum (via Hedley extraction). Additionally, linear combination fitting results of the ditch sample indicate 10.5% organic P and 73.9% P associated with iron and aluminum. This is an important finding because sulfate is a prevalent ion in sea water, and many agricultural soils with high legacy P in the Delmarva coastal area are threatened by sea level rise and inundation.

Liquid Anaerobic Digestate as Sole Nutrient Source in Soilless Horticulture-Or Spiked With Mineral Nutrients for Improved Plant Growth

Digestate from biogas production high in plant-available macro- and micro-nutrients could replace mineral fertilizer in protected (soilless) horticulture. Previous uses of digestate have shown that low concentrations of plant-available phosphorus (P) and sulfur (S) may be limiting factors for growth when using digestate as the sole fertilizer. In this study, digestate collected from a municipal biogas plant in Sweden was nitrified in a moving-bed biofilm reactor prior to its use as fertilizer. A greenhouse pot trial with pak choi grown in peat-based growing medium was established to assess the (i) macro- and micro-nutrient availability in the digestate, with particular focus on P and S and (ii) the effect of amending the digestate solution with nutrients considered to be lacking [P, S, magnesium (Mg), manganese (Mn), boron (B), and molybdenum (Mo)]. The results showed that plants fertilized with raw digestate suffered from S and B deficiency and early P deficiency. Supplementing the digestate with nutrients originating from mineral salts resulted in sufficient plant tissue concentrations of all elements except S. The marketable yield was similar to that achieved using standard mineral fertilizer and the dry matter yield was 17% higher. In the light of the present results, the use of nitrified digestate in soilless plant production seems like a fruitful way forward to recycle organic nutrients from waste streams. In the case where a strict organic protocol is not needed, amendment with inorganic nutrients may be a way to increase the utilization of organically derived nutrients.

Adapted Hedley fractionation for the analysis of inorganic phosphate in biogas digestate

The major share of phosphate in biogas digestate is inorganic. For optimized nutrient recovery, inorganic phosphate must be analyzed adequately. Therefore, the photometric spectra of extracts from Hedley fractionation were measured and analyzed for their peaks using the molybdenum blue method. The ideal wavelength was 709 nm. The lower calibration limit needed to be raised from 15 µg L^-1 to 50 µg L^-1 to avoid underestimation of phosphate concentration. Drying digestate before extraction increased H₂O-P by 78.4% and NaHCO₃-P by 44.9% compared to undried digestate. The filter paper of the filtration between extractions was added to the next extraction to avoid phosphate losses. This made it necessary to rinse the samples with 30 mL deionized H₂O after the H₂O extraction, with 60 mL NaHCO₃ after NaHCO₃ extraction and 60 mL NaOH after the NaOH extraction. Ultimately, the results showed that the phosphate concentration in extracts was independent of extraction time.

Behavior of fast and slow phosphorus release from sewage sludge-derived biochar amended with CaO

The pyrolyzation of sewage sludge (SS) could efficiently transform inherent phosphorus (P) into bioavailable phosphate forms, which endows SS-derived biochar (SSB) the potential as a soil fertilizer. However, the details about the release behavior of P in SSB have not been systematically investigated. This study evaluated the fast and slow P releasing behaviors from SSB and CaO-amended SSB prepared under different pyrolysis temperature. The higher pyrolysis temperature and CaO addition could enhance the conversion of non-apatite inorganic phosphorus (NAIP) into more bioavailable apatite inorganic phosphorous (AP). Acidic and alkaline conditions were favorable for the fast release of P from SSB. Higher ionic strength condition gave greater releasing amounts of TP and the SO₄^2- facilitating a rapid release of TP than those for Cl^- and NO₃^-. SSBs with CaO addition showed a much slower TP release than those without CaO both in fast release (24 h, with CaO: 0.05~0.4 mg TP g^-1 SSB, e.g., without CaO 0.5~5 mg TP g^-1 SSB) and slow release tests (21 days, with CaO: 1.2~4.1 mg TP g^-1 SSB, e.g., without CaO 1.8~5.7 mg TP g^-1 SSB). Ortho-P release was more remarkable for the SSB amended with CaO (~54% of TP), which was likely due to the formation of orthophosphate. The results of this study suggested that SSB prepared by high pyrolysis temperature and CaO addition had high potential as a slow P-releasing fertilizer for the soil.

High doses of phytase on growth performance, bone mineralization, diet utilization, and plasmatic myo-inositol of turkey poults

An experiment was conducted to evaluate the growth performance, bone mineral composition, diet utilization, and plasmatic concentration of myo-inositol (MYO) in turkeys fed different phytase doses from 1 to 28 d. A total of three hundred and twenty 1-day-old turkeys were distributed in a completely randomized design with 4 treatments and 8 replicates of 10 birds each. Treatments included a basal diet without phytase; reduced diet (reduced -0.15% available P and -0.18% Ca) without phytase; reduced diet + 2,000 units of phytase (FYT)/kg; and reduced diet + 4,000 FYT/kg. From day 26 to 28, partial excreta collection was conducted, and on day 28, 7 birds per replicate were euthanized for collection of ileal content and left tibia bones were removed from 2 of the same euthanized birds. Feed, excreta, and ileal digesta samples were analyzed to determine nutrient digestibility and metabolizability, ileal digestible energy, and AME. Tibia bones were analyzed for ash, Ca, and P content, and calculation of Seedor index. On day 28, blood samples were collected from 2 turkeys per replicate to analyze plasmatic MYO concentration. Feed conversion ratio was not affected, but phytase supplementation resulted in higher feed intake and body weight gain compared to turkeys fed the reduced diet (P < 0.05), and both doses were similar to the basal diet. Increasing the phytase dose had a linear effect (P < 0.05) on ileal digestibility of P and metabolizability of DM, CP, Ca, and Na, and also on AME. P content in the tibia bone increased linearly (P < 0.05) with phytase supplementation, and the same linear increase (P < 0.05) was observed for plasmatic MYO. In conclusion, the supplementation of turkey poult's diets with high levels of phytase up to 4,000 FYT/kg improves diet utilization by increasing P digestibility and dietary metabolizability, leading to higher P content in the bone and enhancing MYO provision and absorption.

Renewable P sources: P use efficiency of digestate, processed animal manure, compost, biochar and struvite

In the attempt to close nutrient cycles, organic fertilizers and soil improvers are getting interest as renewable P sources for crops. However, both the P availability of these compounds for crops and the underlying mechanisms are not fully understood. In this study composts (n = 8), biochars (n = 5), animal manure and processed animal manure (n = 13), digestates and processed digestates (n = 15) and blends of digestates with compost/animal manure/mineral fertilizers (n = 15) were analyzed for chemical composition, organic matter stability and P use efficiency (PUE). Biodegradability (=holocellulose/lignin ratio) proved to be a good indicator for organic matter stability and can successfully replace time-consuming incubation experiments in standard analyses of organic fertilizers. The PUE of digestates, struvites, animal manure products and blends of digestate with compost/animal manure/mineral fertilizers was determined by the NH₄⁺-N, Mg and Fe content of the organic fertilizers. The PUE can be predicted by PUE = 61.34 + 8.59*NH₄⁺-N/P + 42.25*Mg/P - 8.09*Fe/P (R² = 0.71). As increasing amounts of NH₄⁺-N and Mg stimulate the formation of soluble struvite crystals, increasing PUE is explained by an increasing amount of P as struvite. The PUE of biochars and composts was determined by the Ca/P and Al content of the organic fertilizers. Here, PUE can be predicted by PUE = 88.87-1.07*Ca/P + 6.08*Al/P (R² = 0.93). As increasing amounts of Ca stimulate the formation of highly stable apatite crystals, increasing PUE is explained by an increasing amount of P in the form of apatite.

Influence of anaerobic digestion on the labile phosphorus in pig, chicken, and dairy manure

Phosphorus (P) loss from livestock and poultry industry causes serious threat to agro-ecological environments. Anaerobic digestion (AD), through recycling of P-containing resources and biogas production, prevails as a promising solution to the resource, energy, and environment trilemma. In this study, the dynamic transformation of P in batch AD processes fed with chicken, pig and dairy manures was investigated. Results showed that the Labile-P of total phosphorus (TP) in pig, chicken and dairy manure digestates decreased from 37.35% to 23.79%, 36.79% to 17.29%, and 60.47% to 20.39%, respectively, and was associated with an increase of NaOH-P during the AD process. However, the Labile-P in raw manures ranging from 64.67% to 81.10%, indicated that AD could reduce the pollution risk caused by the overuse of high Labile-P animal manure as fertilizer. Metal ions had a significant influence on P transformation because of their ability to combine with PO₄^3-/HPO₄^2-. During AD, the species of phosphates increased: AlPO₄, FePO₄, Mg₃(PO₄)₂, CaHPO₄, Mg(NH₄)PO₄·6H₂O and Ca₁₀(PO₄)₆(OH)₂ were the main phosphates qualified by X-ray diffraction (XRD). AD produced a satisfactory fertilizer for plants that were able to activate the precipitated P, which could provide readily available N and slow-release P. This study provides a meaningful theoretical guide for recycling P from animal manure resources.

Molecular Scale Studies of Phosphorus Speciation and Transformation in Manure Amended and Microdose Fertilized Indigenous Vegetable Production Systems of Nigeria and Republic of Benin

This study investigated the speciation, transformation, and availability of P during indigenous vegetable production by employing a combination of chemical and spectroscopic techniques. The study focused on sites in two ecozones of SSA, the dry savanna (lna, Republic of Benin) and rainforest (Ilesha, Nigeria). Both sites were cultivated with two indigenous vegetable species: local amaranth (Amaranthus cruentus (AC)) and African eggplant (Solanum macrocarpon (SM)). The soils were treated with 5 t/ha poultry manure and urea fertilizer at the rates of 0, 20, 40, 60, and 80 kg N/ha. Soil samples were collected before planting and after harvest. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was used to determine P speciation in these soils. Quantitative analysis showed that adsorbed and organic P were the two dominant P species in the manure amended dry savanna (DS) soils before planting and after harvest in soils cultivated with both AC and SM, with the addition of urea (40 kg N/ha) causing an increase in the organic P form in dry savanna soils cultivated with AC. Soils of the rainforest (RF) cultivated with AC initially had large amounts of apatite P in the manure amended soils prior to planting, which was transformed to adsorbed and organic P after harvest. Urea addition to the rainforest soils shifted the dominant P species from organic P to adsorbed and apatite P, which was likely to limit P availability. Soils cultivated with SM had similar proportions of both organic and adsorbed P forms, with 40 kg N/ha addition slightly increasing the proportion of adsorbed P.

Fertilizing potential and CO2 emissions following the utilization of fresh and composted food-waste anaerobic digestates

Wet and dry-batch anaerobic digestion, and composting are common technologies in food waste (FW) management, resulting in different outputs. However, the effects of composting on carbon dioxide (CO₂) emissions, nitrogen (N) and phosphorus (P) fertilizing capacity in view of closing nutrient cycle are still poorly investigated. In this work, two FW anaerobic digestates from the wet (D₁) and dry-batch process (D₂), and their respective composts (C₁ and C₂) were tested in a soil incubation (84 days at 25 °C) to assess CO₂ emissions in comparison with a mixed (animal slurry/energy crop) digestate (BD) and a reference municipal solid waste compost (MSWC). The same products were also tested for the relative P efficiency (RPE) in soil, in comparison with a chemical-P source (30 mg P kg^-1). Lastly, the apparent recovery fraction of N (N-ARF) from the five organic products was determined in a pot test with ryegrass (84 days; 300 kg available N ha^-1), compared to a chemical fertilizer (NPK). Composting strongly reduced net-CO₂ emissions compared to the two digestates (625 vs. 2850 mg CO₂ kg^-1 soil). Oppositely, composting very modestly influenced RPE that ranged around 100-90% in D₁ and C₁, and ≈30% in D₂ and C₂. Moreover, composting did not significantly reduce N-ARF that ranked in descending order as follows: NPK (77.5%) > D₁ = BD (17.7%) ≥ C₁ (14.7%) > MSWC (3.6%) > D₂ (1.2%) > C₂ (-3.1%). Composting was shown a reliable strategy for FW digestate management, as it reduces potential CO₂ emission without affecting these products' N- and P-fertilizing capacity.

Organic wastes as alternative sources of phosphorus for plant nutrition in a calcareous soil

Recycled organic wastes (OW) can be a valuable P source; however, their P-fertilising capacity is still poorly known. In this study, we selected three anaerobic digestates [wastewater sludge (D₁), winery sludge (D₂), and bovine-slurry/energy crops (BD)] and two animal effluents [bovine slurry (BS) and swine slurry (SS)] to test their P-release and P-fertilising capacities via sequential chemical extraction (SCE), X-ray diffraction (XRD), and ³¹P-nuclear magnetic resonance (³¹P NMR). Subsequently, the three digestates (30 mg P kg^-1 of soil) were compared for the release of Olsen-P during a soil incubation and for plant-P apparent recovery (ARF) in a pot experiment using ryegrass (112 days) in a soil with poorly available-P (Olsen-P < 5 mg kg^-1), under a non-limiting N environment. The amount of labile-P (H₂O + NaHCO₃), as determined from SCE, related well to the Olsen-P following OW addition to the soil. It was shown via ³¹P NMR spectroscopy that orthophosphate was the leading P-form in highly P-releasing OW. The amount of labile-P, however, was affected by soil adsorption, thereby reducing plant-P uptake. The plant-P ARF (%) showed that the recycled P-sources were clustered in highly (BD and SS: ≈20%), intermediately (D₁ and BS: ≈15%), and poorly performing OWs (D₂: ≈10%) vs. chemical P-source (P-chem: 20%). Therefore, only BD and SS were effective alternatives to P-chem; however, the other OW can be efficient P-sources in soils with higher Olsen-P. Thus, crop fertilisation can be tailored on a P-basis by SCE as a function of soil adsorption capacity and on an N-basis according to the demand.

Mechanisms of Phosphorus Removal by Phosphorus Sorbing Materials

Stormwater filters are a structural best management practice designed to reduce dissolved P losses from runoff. Various industrial byproducts are suitable for use as P sorbing materials (PSMs) for the treatment of drainage water; P sorption by PSMs varies with material physical and chemical properties. Previously, P removal capacity by PSMs was estimated using chemical extractions. We determined the speciation of P when reacted with various PSMs using X-ray absorption near edge structure (XANES) spectroscopy. Twelve PSMs were reacted with P solution in the laboratory under batch or flow-through conditions. In addition, three slag materials were collected from working stormwater filtration structures. Phosphorus K-edge XANES spectra were collected on each reacted PSM and compared with spectra of 22 known P standards using linear combination fitting in Athena. We found evidence of formation of a variety of Ca-, Al-, and/or Fe-phosphate minerals and sorbed phases on the reacted PSMs, with the exact speciation influenced by the chemical properties of the original unreacted PSMs. We grouped PSMs into three general categories based on the dominant P removal mechanism: (i) Fe- and Al-mediated removal [i.e., adsorption of P to Fe- or Al-(hydro-)oxide minerals and/or precipitation of Fe- or Al-phosphate minerals]; (ii) Ca-mediated removal (i.e., precipitation of Ca-phosphate mineral); and (iii) both mechanisms. We recommend the use of Fe/Al sorbing PSMs for use in stormwater filtration structures where stormwater retention time is limited because reaction of P with Fe or Al generally occurs more quickly than Ca-P precipitation.

Water-Extractable Phosphorus in Animal Manure and Manure Compost: Quantities, Characteristics, and Temporal Changes

Water-extractable P (WEP) in manure and manure compost is widely used as an indicator of P release to runoff from manure and compost that are land applied. A survey of 600 manures and composts was conducted to assess trends in WEP (dry weight equivalent) related to manure and compost types from sources in the Mid-Atlantic region. Manure and compost WEP ranged from 0.2 to 20.8 g kg. Mean WEP was highest in turkey and swine manures (manure: 4.1-5.6 g kg; no composts tested), followed by layer and broiler chicken manures (manure: 3.0-3.5 g kg; compost: 4.6-5.1 g kg), cattle manure (dairy and beef manure: 2.1-2.8 g kg; compost: 1.1-2.7 g kg), and horse manure (manure: 2.7 g kg; compost: 1.9 g kg). Across all manures and composts, WEP was negatively correlated with manure dry matter content ( = 0.42, < 0.001). Moreover, WEP was strongly correlated ( = 0.66, < 0.001) to degree of P saturation expressed as a molar ratio of total P to total metals (Ca, Mg, Fe, Al, and Mn). Although WEP levels of beef, broiler chicken, and turkey manures from this survey are similar to those from a decade ago, WEP is now significantly lower for dairy (30%, < 0.001), swine (46%, < 0.001), and layer chickens (39%, < 0.05). Lower WEP resulted from decreasing total P and/or increasing P sorption capacity, combined with increasing dry matter content. Results highlight the potential to use degree of P saturation to predict WEP and suggest an opportunity to reduce WEP by managing manure handling, storage, and chemistry.

Transformations of Phosphorus Speciation during (Hydro)thermal Treatments of Animal Manures

Phosphorus (P) in animal manures is an important P pool for P recycling and reclamation. In recent years, thermochemical techniques have gained much interests for effective waste treatment and P recycling. This study comparatively characterized the transformation of P during two representative thermochemical treatments (pyrolysis and hydrothermal carbonization, HTC) of four animal manures (swine, chicken, beef, and dairy manures) by combining nuclear magnetic resonance spectroscopy, X-ray absorption spectroscopy, and sequential extraction. For both pyrolysis and HTC treatments, degradation of organic phosphate and crystallization of Ca phosphate minerals were observed and were highly dependent on treatment temperature. Extensive crystallization of Ca phosphate minerals occurred at temperatures above 450 °C during pyrolysis, compared to the lower temperature (175 and 225 °C) requirements during HTC. As a result, P was immobilized in the hydrochars and high temperature pyrochars, and was extracted primarily by HCl. Because Ca is the dominating P-complexing cation in all four manures, all manures showed similar P speciation and transformation behaviors during the treatments. Results from this work provided deeper insights into the thermochemical processes occurred during the pyrolysis and HTC treatments of biological wastes, as well as guidance for P reclamation and recycling from these wastes.

The Contrasting Effects of Alum-Treated Chicken Manures and KH2PO4 on Phosphorus Behavior in Soils

Alum [KAl(SO)⋅12HO] is often added to chicken manure to limit P solubility after land application. This is generally ascribed to the formation of Al-PO complexes. However, Al-PO complex formation could be affected by the matrix of chicken manure, which varies with animal diet. Alum was added to KHPO (as a reference material) and two manures from typical chicken farms in China, one from an intensive farm (CMIF) and another from free-ranging chickens (CMFR). These were subsequently incubated with soils for 100 d to investigate P transformations. Alum reduced water-soluble colorimetrically reactive phosphorus (RP) from soils amended with manure more effectively than in soils amended with KHPO. Alum addition lowered Mehlich-3 RP in soils with CMFR but had no influence on Mehlich-3 RP in CMIF- or KHPO-amended soils. A comparison of P in digested Mehlich-3 extracts with RP in undigested samples showed significantly increased P in digests of alum-treated CMFR only. Fractionation data indicated that alum treatment increased P in the NHF-RP (Al-P) fraction only in soils with KHPO, but not in soils with manure treatments. Furthermore, NaOH-extracted nonreactive P was markedly higher in soil with alum-treated CMFR relative to normal CMFR. The CMFR manure was assumed to contain higher concentrations of organic P because these chickens were fed grains only. These results suggest that the formation of alum-organic P complexes may reduce P solubility. By comparing alum-treated KHPO and manures, it appears that organic matter in manure could interfere with the formation of Al-PO complexes.

Phosphorus speciation in a prairie soil amended with MBM and DDG ash: Sequential chemical extraction and synchrotron-based XANES spectroscopy investigations

Sequential chemical extraction and synchrotron-based XANES spectroscopy techniques were used to identify P species in two ashes before and after addition to a prairie soil. The used ashes were: meat and bone meal ash (MBMA) and dried distillers grains ash (DDGA) plus mineral P fertilizer (MP) for comparison. Soil treated with MP contained higher content of resin-Pi and NaHCO₃-Pi followed by DDGA and MBMA. The MBMA amended soil had the highest (47%) proportion of the soil P contained in recalcitrant HCl extractable fraction, reflecting more Ca-bound P present and being formed in soil after application. Analysis of both ashes with XANES spectroscopy before application to soil revealed that MBMA had strong spectral features consistent with hydroxyapatite (Ca₅(PO₄)₃(OH)). DDGA exhibited spectral features consistent with a mixture of several Mg and K phosphate salts rather than a single mineral species. The distinctive features in the XANES spectra of both ashes largely disappeared after amendment to the soil, suggesting transformation to different P forms in the soil after application. It is also possible that the added amount of P to the studied soil via DDGS or MBMA was small enough so that P speciation is not different from the background P level.

Effect of iron sulphate on the phosphorus speciation from agro-industrial sludge based and sewage sludge based compost

Composting is considered a suitable process for organic waste management, providing stable products that can be safely utilized as fertilizers, but little is still known about the variation of phosphorous (P) extractability during the stabilization process. In this work, sequential chemical extraction (SCE) with increasing strength extractants (H₂O; 0.5M NaHCO₃ pH 8.5; 0.1M NaOH, 1M HCl) was applied for P speciation over 56days of composting of either agro-industrial or urban wastewater sludge with green waste treated (AIC_Fe+; SSC_Fe+) or not (AIC_Fe-; SSC_Fe-) with FeSO₄ (2%v/v). Composting strongly reduced the H₂O-P, promoting the organic-P (P_o) mineralization from the labile fraction (H₂O+NaHCO₃ 40%), in addition to the increases of NaHCO₃- and HCl-extractable inorganic-P (P_i) in both AIC_Fe- and SSC_Fe- (+20% on average). The FeSO₄ treatment did not negatively affect the process, reducing the P_o mineralization during composting by increasing the NaOH-P, also protecting this fraction from fixation in the sparingly soluble fraction. The final P fractionation (%) was in AIC_Fe-: NaOH (41)=NaHCO₃ (38)>HCl (18)>H₂O (3); in AIC_Fe+: NaOH (53)>NaHCO₃ (24)=HCl (22)>H₂O (2); in SSC_Fe-: NaOH (46)>NaHCO₃ (29)>HCl (21)>H₂O (4) and in SSC_Fe+: NaOH (66)>NaHCO₃ (13)>HCl (20)>H₂O (1). Composting reduced the more easily leachable fraction (labile-P_o), reducing the risk of P loss by increasing the long-term available P fraction (NaOH-P). This was enhanced by the FeSO₄ addition. Further investigation into soil behaviour and plant availability of P from this source is needed.

Transformation of Phosphorus during (Hydro)thermal Treatments of Solid Biowastes: Reaction Mechanisms and Implications for P Reclamation and Recycling

Phosphorus (P) is an essential nutrient for all organisms, thus playing unique and critical roles at the food-energy-water nexus. Most P utilized by human activities eventually converges into various solid biowastes, such as crop biomass, animal manures, and sewage sludges. Therefore, integration of efficient P recovery practices into solid biowaste management will not only significantly reduce the dependence on limited geological P resources but also reduce P runoff and related water contamination issues associated with traditional waste management strategies. This study reviews the applications of (hydro)thermal techniques for the treatment of solid biowastes, which can greatly facilitate P recovery in addition to waste volume reduction, decontamination, and energy recovery. Research showed that P speciation (including molecular moiety, complexation state, and mineralogy) can experience significant changes during (hydro)thermal treatments, and are impacted by treatment techniques and conditions. Changes in P speciation and overall properties of the products can alter the mobility and bioavailability of P, and subsequent P reclamation and recycling efficiency of the treatment products. This review summarizes recent progresses in this direction, identifies the challenges and knowledge gaps, and provides a foundation for future research efforts targeting at sustainable management of nutrient-rich biowastes.

Recycled Products from Municipal Wastewater: Composition and Effects on Phosphorus Mobility in a Sandy Soil

Recycled products from wastewater may contain high concentrations of phosphorus (P) and are thus promising alternative fertilizers. However, to better predict their P fertilizer efficiency and potential for P leaching, investigations on P forms and P mobility in soil are essential. In this study, different recycled products-an untreated sewage sludge ash (SSA), an HSO-digested SSA, four thermochemically treated SSAs (two Mg-SSAs and two Ca-SSAs), and struvite-were investigated using a combination of wet chemical methods and P K-edge X-ray absorption near-edge structure (XANES) spectroscopy concerning their composition and their effects on P sorption in a sandy soil in comparison to triple superphosphate. Most of the P in the SSAs was associated with Ca in stable P fractions. The lowest P values in labile fractions (HO-P, NaHCO-P) were found for the untreated SSA and struvite. However, the addition of struvite resulted in an immediate increase in the bioavailable P fractions and the degree of P saturation in soil after only 1 d of incubation. This suggests a high P fertilizer potential for struvite but also a risk of P losses. Among the SSAs, the two Mg-SSAs increased the bioavailable P fractions in soil the most, whereas the lowest values were measured after application of the untreated SSA. Our results demonstrate that chemical analyses of recycled P products may involve the risk of misjudging the fertilizer quality when performed alone, without considering the behavior of these products in soil.

The effect of different pyrolysis temperatures on the speciation and availability in soil of P in biochar produced from the solid fraction of manure

Biochar application to agricultural land has been proposed as a means for improving phosphorus (P) availability in soil. The purpose of the current study was to understand how pyrolysis temperature affects P speciation in biochar and how this affects availability of P in the amended soil. Biochar was produced at different temperatures from digestate solids. The primary species of P in digestate solids were simple calcium phosphates. However, a high co-occurrence of magnesium (Mg) and P, indicated that struvite or other magnesium phosphates may also be important species. At low temperatures, pyrolysis had little effect on P speciation; however, as the temperature increased above 600 °C, the P gradually became more thermodynamically stable in species such as apatite. At very high temperatures above 1000 °C, there were indications of reduced forms of P. Biochar production decreased the immediate availability of P in comparison with the original digestate solids. However, for biochar produced at low temperatures, availability quickly increased to the same levels as in the digestate solids. For biochar produced at higher temperatures, availability remained depressed for much longer. The low availability of P in the biochar produced at high temperatures can probably be explained by the formation of less soluble P species in the biochar. In contrast, the transient decrease of availability of the P in the biochar produced at low temperatures can be explained by mechanisms, such as sorption on biochar, which gradually decreases because of oxidation of the biochar surfaces or changes in pH around the biochar particles.

Using FTIR-photoacoustic spectroscopy for phosphorus speciation analysis of biochars

In the last decade, numerous studies have evaluated the benefits of biochar for improving soil quality. The purposes of the current study were to use Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) to analyse P species in biochar and to determine the effect of pyrolysis temperature on P speciation. The photoacoustic detector has a range of advantages for the very dark biochar samples in comparison to more traditional reflectance or transmission FTIR detectors. The spectra turned out to be more informative in the regions with P vibrations for biochar produced at temperatures above 400°C, where most of the remaining organic compounds were aromatic and therefore not overlapping with the P vibrations. For biochars produced from the solid fraction of digestate from biogas production, an increase in the pyrolysis temperature led to the formation of a large variety of P species. Hydroxylapatite and tricalcium phosphate were the most dominant P species in the mid to high temperature range (600-900°C), while at 1050°C apatite, iron phosphates, variscite and calcium phosphates were identified. However, the changes in P speciation in biochars produced from bone meal at different temperatures were smaller than in the biochars from digestate. Hydroxylapatite and calcium phosphates were identified in biochar produced at all temperatures, while there was some indication of struvite formation.

Phosphorus Leaching in Soils Amended with Animal Manures Generated from Modified Diets

New dietary modifications for dairy (reducing P content in feed) and poultry (addition of feed additives such as phytase) aim to reduce P excretion in manures. Our objective was to investigate if dietary changes were effective at reducing P leaching loss on land application of manures. We used 54 undisturbed lysimeters (30 cm diameter, 50 cm deep) collected from three typical mid-Atlantic soils. Lysimeters received 85 kg total P ha from fertilizer (superphosphate), dairy manures generated from low- or high-P diets, or broiler litters generated from normal diet or reduced P- and phytase-amended diets. Lysimeters were irrigated with 50 mm of water each week for 9 wk. The major forms of P in the leachate were dissolved (dissolved unreactive > dissolved reactive P [DRP]) rather than particulate (total particulate P). The higher P solubility (100%) in superphosphate resulted in greater leaching of DRP, whereas the lower P solubility (<30%) in dairy manures or broiler litters resulted in lower DRP leaching from soils. Preferential flow in two soils caused greater DRP leaching; this effect was more pronounced in the superphosphate-amended than in the manure/litter-amended lysimeters. The dairy and poultry dietary modification was effective at reducing the amount of P in manures and litters. However, the application of treatments at similar P rate (85 kg ha) resulted in the addition of a higher amount of manure (54-66%) in lysimeters that received low-P dairy manure-amended and phytase-amended broiler litter, which then controlled P leaching from soils.

Wading bird guano enrichment of soil nutrients in tree islands of the Florida Everglades

Differential distribution of nutrients within an ecosystem can offer insight of ecological and physical processes that are otherwise unclear. This study was conducted to determine if enrichment of phosphorus (P) in tree island soils of the Florida Everglades can be explained by bird guano deposition. Concentrations of total carbon, nitrogen (N), and P, and N stable isotope ratio (δ(15)N) were determined on soil samples from 46 tree islands. Total elemental concentrations and δ(15)N were determined on wading bird guano. Sequential chemical extraction of P pools was also performed on guano. Guano contained between 53.1 and 123.7 g-N kg(-1) and 20.7 and 56.7 g-P kg(-1). Most of the P present in guano was extractable by HCl, which ranged from 82 to 97% of the total P. Total P of tree islands classified as having low or high P soils averaged 0.71 and 40.6 g kg(-1), respectively. Tree island soil with high total P concentration was found to have a similar δ(15)N signature and total P concentration as bird guano. Phosphorus concentrations and δ(15)N were positively correlated in tree island soils (r = 0.83, p< 0.0001). Potential input of guano with elevated concentrations of N and P, and (15)N enriched N, relative to other sources suggests that guano deposition in tree island soils is a mechanism contributing to this pattern.

Standard Protocol and Quality Assessment of Soil Phosphorus Speciation by P K-Edge XANES Spectroscopy

Phosphorus (P) in soils is most often bound as phosphate to one or more of the following four elements or compounds: calcium, aluminum, iron, and soil organic matter. A promising method for direct P speciation in soils is synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy at the K-edge of P. However, the quality of this method is debated controversially, partly because a standard protocol for reproducible spectrum deconvolution is lacking and minor modifications of the applied deconvolution procedure can lead to considerable changes in the P speciation results. On the basis of the observation that appropriate baseline correction and edge-step normalization are crucial for correct linear combination (LC) fitting results, we established a standard protocol for the deconvolution and LC fitting of P K-edge XANES spectra. We evaluated the quality of LC fits obtained according to this standard protocol with 16 defined dilute (2 mg P g(-1)) ternary mixtures of aluminum phosphate, iron phosphate, hydroxyapatite, and phytic acid in a quartz matrix. The LC fitting results were compared with the contribution of the different P compounds to total P in the various mixtures. Compared to using a traditional LC fitting procedure, our standard protocol reduced the fitting error by 6% (absolute). However, P portions smaller than 5% should be confirmed with other methods or excluded from the P speciation results. A publicly available database of P K-edge XANES reference spectra was initiated.

Phytate (Inositol Hexakisphosphate) in Soil and Phosphate Acquisition from Inositol Phosphates by Higher Plants. A Review

Phosphate (P) fixation to the soil solid phase is considered to be important for P availability and is often attributed to the strong binding of orthophosphate anion species. However, the fixation and subsequent immobilization of inositolhexa and pentaphosphate isomers (phytate) in soil is often much stronger than that of the orthosphate anion species. The result is that phytate is a main organic P form in soil and the dominating form of identifiable organic P. The reasons for the accumulation are not fully clear. Two hypothesis can be found in the literature in the last 20 years, the low activity of phytase (phosphatases) in soil, which makes phytate P unavailable to the plant roots, and, on the other hand, the strong binding of phytate to the soil solid phase with its consequent stabilization and accumulation in soil. The hypothesis that low phytase activity is responsible for phytate accumulation led to the development of genetically modified plant genotypes with a higher expression of phytase activity at the root surface and research on the effect of a higher phytate activity on P acquisition. Obviously, this hypothesis has a basic assumption, that the phytate mobility in soil is not the limiting step for P acquisition of higher plants from soil phytate. This assumption is, however, not justified considering the results on the sorption, immobilization and fixation of phytate to the soil solid phase reported in the last two decades. Phytate is strongly bound, and the P sorption maximum and probably the sorption strength of phytate P to the soil solid phase is much higher, compared to that of orthophosphate P. Mobilization of phytate seems to be a promising step to make it available to the plant roots. The excretion of organic acid anions, citrate and to a lesser extend oxalate, seems to be an important way to make phytate P available to the plants. Phytase activity at the root surface seems not be the limiting step in P acquisition from phytate. Phytate is not only bound to inorganic surfaces in soil but can also be bound, similar to orthophosphate, to humic surfaces via Fe or Al bridges. Humic-metal-phytate complexes may be transported in the soil solution to the roots where hydrolysis and uptake of the liberated P may occur. Research on this topic is strongly required.

Changes in phosphorus fractions during organic wastes composting from different sources

The study was conducted to investigate the changes in different fractions of phosphorus (P) and the relationship between different P fractions and their corresponding physicochemical parameters during organic wastes composting. There were distinct differences in the concentration of P fractions for the composts generated from different sources, highest in chicken manure and pig manure. The availability P (including water soluble P, Olsen P and citric acid P) declined from 44% to 36% in all composts, except for KW, following the thermophilic phase during composting, while moderately available P and non-available P increased from 48% to 59%. Different P fractions (inorganic P, organic P, Olsen P, water soluble P and citric acid P) were positively correlated with each other. The composts were clustered into two groups in our hierarchical cluster analysis. Conclusively, we suggested an optimized mode of composting based on the characteristics of the P fractions from different raw materials.

Recycling slaughterhouse waste into fertilizer: how do pyrolysis temperature and biomass additions affect phosphorus availability and chemistry?

BACKGROUND

Pyrolysis of slaughterhouse waste could promote more sustainable phosphorus (P) usage through the development of alternative P fertilizers. This study investigated how pyrolysis temperature (220, 350, 550 and 750 °C), rendering before pyrolysis, and wood or corn biomass additions affect P chemistry in bone char, plant availability, and its potential as P fertilizer.

RESULTS

Linear combination fitting of synchrotron-based X-ray absorption near edge structure spectra demonstrated that higher pyrolysis temperatures decreased the fit with organic P references, but increased the fit with a hydroxyapatite (HA) reference, used as an indicator of high calcium phosphate (CaP) crystallinity. The fit to the HA reference increased from 0% to 69% in bone with meat residue and from 20% to 95% in rendered bone. Biomass additions to the bone with meat residue reduced the fit to the HA reference by 83% for wood and 95% for corn, and additions to rendered bone by 37% for wood. No detectable aromatic P forms were generated by pyrolysis. High CaP crystallinity was correlated with low water-extractable P, but high formic acid-extractable P indicative of high plant availability. Bone char supplied available P which was only 24% lower than Triple Superphosphate fertilizer and two- to five-fold higher than rock phosphate.

CONCLUSION

Pyrolysis temperature and biomass additions can be used to design P fertilizer characteristics of bone char through changing CaP crystallinity that optimize P availability to plants.

Formations of hydroxyapatite and inositol hexakisphosphate in poultry litter during the composting period: sequential fractionation, P K-edge XANES and solution (31)P NMR investigations

Little is known about how the solubility and chemical speciation of phosphorus (P) in poultry litters are altered during the composting period. This study investigated the quantitative and qualitative changes in organic P (Po) and inorganic P (Pi) compositions in poultry litters during the seven-day composting period using sequential extraction in combination with P K-edge X-ray absorption near-edge structure (XANES) and solution (31)P nuclear magnetic resonance (NMR) spectroscopy. The result of sequential extraction illustrated that the significant decrease of H2O-P by 55% in poultry litters occurred concomitantly with the increase of HCl-Pi and HCl-Po during the composting period (p < 0.05). X-ray diffraction results for poultry litter samples showed three distinct peaks indicative of hydroxyapatite. Phosphorus K-edge XANES confirmed the increase of hydroxyapatite during the composting period, corresponding to the increase of HCl-Pi determined by the sequential extraction. The NaOH-EDTA extraction for solution (31)P NMR revealed that myo-inositol hexakisphosphate (IHP) constituted about 80% of phosphate monoesters and was increased from 16 to 28% in the poultry litter during the composting period. The combined applications of chemical extraction and molecular-spectroscopic techniques determined that water-soluble P in poultry litter was transformed into less soluble phases, primarily hydroxyapatite and IHP, during the composting period.

Complementary Phosphorus Speciation in Agricultural Soils by Sequential Fractionation, Solution P Nuclear Magnetic Resonance, and Phosphorus K-edge X-ray Absorption Near-Edge Structure Spectroscopy

Ultisols in China need phosphorus (P) fertilization to sustain crop production but are prone to P loss in runoff. Balancing P inputs and loss requires detailed information about soil P forms because P speciation influences P cycling. Analytical methods vary in the information they provide on P speciation; thus, we used sequential fractionation (SF), solution P nuclear magnetic resonance (P-NMR), and P K-edge X-ray absorption near-edge structure (XANES) spectroscopy to investigate organic P (P) and inorganic P (P) species in Chinese Ultisols managed for different crops and with different fertilizer inputs in the first study to combine these techniques to characterize soil P. Sequential fractionation showed that moderately labile NaOH-P was the largest P pool in these soils, P varied from 20 to 47%, and residual P ranged from 9 to 31%. Deoxyribonucleic acid (1-5%) and -inositol hexakisphosphate (-IHP, 4-10%) were the major P forms from P-NMR. Orthophosphate diesters determined by NMR were significantly correlated with labile NaHCO-P in SF ( > 0.981; < 0.001). Soil P was shown to be predominantly associated with iron and soluble calcium (Ca) by XANES. Furthermore, XANES identified hydroxyapatite in the soil receiving the highest rates of Ca-phosphate fertilizer, which had the highest HCl-P pool by SF, and also identified IHP (7%) in the soil with the highest proportion of -IHP from P-NMR. These results strongly suggest that a combined use of SF, solution P-NMR, and P K-edge XANES spectroscopy will provide the comprehensive information about soil P species needed for effective soil P management.

Investigation of the inorganic and organic phosphorus forms in animal manure

The most viable way to beneficially use animal manure on most farms is land application. Over the past few decades, repeated manure application has shown adverse effects on environmental quality due to phosphorus (P) runoff with rainwater, leading to eutrophication of aquatic ecosystems. Improved understanding of manure P chemistry may reduce this risk. In this research, 42 manure samples from seven animal species (beef and dairy cattle, swine, chicken, turkey, dairy goat, horse, and sheep) were sequentially fractionated with water, NaHCO₃, NaOH, and HCl. Inorganic (P(i)), organic (P(o)), enzymatic hydrolyzable (P(e); monoester-, DNA-, and phytate-like P), and nonhydrolyzable P were measured in each fraction. Total dry ash P (P(t)) was measured in all manures. Total fractionated P (P(ft)) and total P(i) (P(it)) showed a strong linear relationship with P(t). However, the ratios between P(ft)/P(t) and P(it)/P(t) varied from 59 to 117% and from 28 to 96%, respectively. Water and NaHCO₃ extracted most of the P(i) in manure from ruminant+horse, whereas in nonruminant species a large fraction of manure P was extracted in the HCl fraction. Manure P(e) summed over all fractions (P(et)) accounted for 41 to 69% of total P(0) and 4 to 29% of P(t). The hydrolyzable pool in the majority of the manures was dominated by phytate- and DNA-like P in water, monoester- and DNA-like P in NaHCO₃, and monoester- and phytate-like P in NaOH and HCl fractions. In conclusion, if one assumes that the P(et) and P(it) from the fractionation can become bioavailable, then from 34 to 100% of P(t) in animal manure would be bioavailable. This suggests the need for frequent monitoring of manure P for better manure management practices.

Spectroscopic approaches for phosphorus speciation in soils and other environmental systems

In the past decades, environmental scientists have become increasingly involved in developing novel approaches for applying emerging spectroscopic techniques to complex environmental matrices. The objective of this review is to convey the most common chemical species of phosphorus reported for soils, sediments, model systems, and waste materials based on analyses by four spectroscopic techniques: X-ray absorption near-edge structure, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and Raman spectroscopy. Unique information is provided by each technique at a level of specificity that depends in part on matrix complexity. The X-ray absorption near-edge structure and nuclear magnetic resonance techniques reveal inorganic and organic P species in intact environmental matrices or in chemical extracts, whereas the Fourier transform infrared and Raman techniques can provide more specific bonding information about mineral or adsorbed P species in model analogs of matrix components. The most common P species in soils and sediments as indicated by spectroscopy are hydroxyapatite and octacalcium phosphate minerals, phosphate adsorbed on Fe- and Al-oxides, pyrophosphates and polyphosphates, phosphate mono- and di-esters, and phosphonates. Continued advancements in spectroscopic methods should improve speciation-based models of P mobilization and transformations in the environment.

Phosphorus speciation in sequentially extracted agro-industrial by-products: evidence from X-ray absorption near edge structure spectroscopy

The phosphorus (P) in agro-industrial by-products--a potential source of freshwater eutrophication but also a valuable fertilizer--needs to be speciated to evaluate its fate in the environment. We investigated to what extent X-ray absorption near edge structure (XANES) spectroscopy at the P K- and L2.3-edges reflected differences in sequentially extracted filter cakes from sugarcane (Saccharum officinarum L.) (FIC) and niger seed (Guizotia abyssinica Cass.; NIC) processing industry in Ethiopia. The P fractionation removed more labile (54%) and H2SO4-P (28%) from FIC than from NIC (18% labile, 12% H2SO4-P). For the FIC residues after each extraction step, linear combination (LC) fitting of P K-edge spectra provided evidence for the enrichment of Ca-P after the NaOH-extraction and its almost complete removal after the H2SO4-treatment. The LC-fitting was unsuccessful for the NIC samples, likely because of the predominance of organic P compounds. The different proportions of Ca-P compounds between FIC (large) and NIC (small) were more distinctive in L2-than in the K-edge XANES spectra. In conclusion, the added value of complementary P K- and L2.3-edge XANES was clearly demonstrated, and the P fractionation and speciation results together justify using FIC and NIC as soil amendments in the tropics.

ATR-FTIR studies on the nature of surface complexes and desorption efficiency of p-arsanilic acid on iron (oxyhydr)oxides

The fate of organoarsenicals introduced to the environment through the application of arsenic-contaminated manure has attracted considerable attention after the recent implementation of the latest maximum contaminant level (MCL) of total arsenic in drinking water by the U.S. Environmental Protection Agency (EPA). We report herein detailed spectroscopic analysis of the surface structure of p-arsanilic acid (p-AsA) adsorbed on Fe-(oxyhydr)oxides using attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Spectra of p-AsA(ads) were collected in situ as a function of pH and ionic strength and using D20 at 298 K in flow mode. Results indicate the formation of inner-sphere complexes, which are likely monodentate and become protonated under acidic pH(D). We also examined the desorption efficiency of p-AsA(ads) due to flowing electrolyte and phosphate solutions as low as 0.1 mol/m3 (3 ppm P) by collecting ATR-FTIR spectra as a function of time. Our results suggest that aqueous phosphate is an efficient desorbing anion of p-AsA(ads), which has implications on its bioavailability and mobility in geochemical environments.

Nutrient excretion, phosphorus characterization, and phosphorus solubility in excreta from broiler chicks fed diets containing graded levels of wheat distillers grains with solubles

Increased interest in ethanol production in North America has led to increased production of distillers dried grains with solubles (DDGS), the majority of which are fed to livestock. To determine the impact of including wheat DDGS in broiler diets on nutrient excretion and P characterization and solubility, 125 one-day-old male broiler chicks were fed wheat- and soybean meal-based diets containing 0, 5, 10, 15, or 20% wheat DDGS. There were 5 replicate pens per treatment, with 5 birds per pen arranged in a randomized block design. Apparent retention of both N and P were determined by using the indicator method. Nutrients excreted per kilogram of DM intake were also calculated. Characterization of excreta P was determined by (31)P-solution nuclear magnetic resonance spectroscopy, and water-soluble P (WSP) was determined by extraction of excreta with deionized water. The apparent retention of both N (P < 0.001) and P (P < 0.008) decreased linearly with increasing inclusion rates of DDGS from 0 to 20%. The nutrient output per kilogram of DM intake increased linearly with increased DDGS inclusion rate for N (P < 0.04), P (P < 0.0001), and WSP (P < 0.0003). As the inclusion rate of DDGS increased, the P concentration in excreta increased (P < 0.008), whereas excreta phytate P concentrations decreased (P < 0.01), which led to an increase in WSP and the fraction of total P that was soluble. Because the inclusion of DDGS in poultry diets increased N and P output, as well as the solubility of P excreted, care should be taken when including high levels of DDGS in poultry diets, because increases in N and P excretion are a concern from an environmental standpoint.

Evaluating phosphorus release from biosolids and manure-amended soils under anoxic conditions

The solubility of P in biosolids and manures has been shown to influence the potential for dissolved P losses in runoff and leachate when these materials are land applied. As a result, some Mid-Atlantic US states have developed P source coefficients (PSCs) to account for differences in P solubility between fertilizers, manures, and biosolids in P risk assessment tools. The reliability of these PSCs has not been evaluated under anoxic conditions, where environmental changes may affect the P solubility of biosolids or manures. The objective of this study was to assess the effects of anoxic conditions on the release of P from a range of Mid-Atlantic soils amended with manures and biosolids. The concentration of dissolved P released into solution (0.01 mol L(-1) NaCl) from the Pamunkey, Berks, and Manor soils was significantly lower under reducing conditions than under oxidized conditions (median DeltaP = -0.70, -0.49, and -0.07 mg L(-1), respectively; all significant at the 0.001 probability level). There was no significant P source effect on dissolved P released into solution after anoxic incubation of soils. Calculated solubility diagrams and increases in oxalate-extractable Fe and P sorption index under reducing conditions for all soils suggest the precipitation of (i) an Fe(II)-oxide that increased the P sorption capacity of the soils or (ii) an Fe(II)-phosphate that decreased the solubility of P. We propose that current PSCs do not need alteration to account for differences in P solubility of organic sources under reducing conditions under relatively static conditions (e.g., seasonable high water table, periodically submerged soils, stagnant drainage ditches).