Combining spectroscopic and isotopic techniques gives a dynamic view of phosphorus cycling in soil

Helfenstein, Julian; Tamburini, Federica; Sperber, Christian von; Massey, Michael S.; Pistocchi, Chiara; Chadwick, Oliver A.; Vitousek, Peter M.; Kretzschmar, Ruben; Frossard, Emmanuel

doi:10.1038/s41467-018-05731-2

Cited by 171 publications

(168 citation statements)

References 64 publications

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“…Often, P XANES spectroscopy, chemical extractions, and even other spectroscopic or isotopic methods are used to support and corroborate results when examining soil P behavior (Helfenstein et al, 2018; Prietzel et al, 2016). But what of the case when plausible results do not fully corroborate each other?…”

Section: Resultsmentioning

confidence: 99%

Mechanisms Responsible for Soil Phosphorus Availability Differences between Sprinkler and Furrow Irrigation

et al. 2019

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From a historical perspective, human‐induced soil erosion and resulting soil phosphorus (P) losses have likely occurred for thousands of years. In modern times, erosion risk and off‐site P transport can be decreased if producers convert from furrow to sprinkler irrigation, but conversion may alter nutrient dynamics. Our study goal was to determine soil P dynamics in furrow‐ (in place since the early 1900s) versus sprinkler‐irrigated (installed within the last decade) soils from four paired producer fields in Idaho. Furrow‐ and sprinkler‐irrigated soils (0–5 cm; Aridisols) contained on average 38 and 20 mg kg−1 of Olsen‐extractable P (i.e., plant‐available P), respectively; extractable P values over 40 mg kg−1 limit Idaho producers to P application based on crop uptake only. Soil samples were also analyzed using a modified Hedley extraction. Furrow‐irrigated soils contained greater inorganic P concentrations in the soluble+aluminum (Al)‐bound+iron (Fe)‐bound, occluded, and amorphous Fe‐bound pools. Phosphorus K‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy was unable to detect Fe‐associated P but indicated greater amounts of apatite‐like or octacalcium phosphate‐like P in furrow‐irrigated producer soils, while sprinkler‐irrigated fields had lower amounts of apatite‐like P and greater proportions of P bound to calcite. Findings from a controlled USDA‐ARS sprinkler‐ versus furrow‐irrigation study suggested that changes in P dynamics occur slowly over time, as few differences were observed. Overall findings suggest that Fe redox chemistry or changes in calcium (Ca)‐associated P in flooded conditions altered P availability under furrow irrigation, even in aridic, calcareous soils, contributing to greater Olsen‐extractable P concentrations in long‐term furrow‐irrigated fields. Core Ideas Irrigation type may greatly affect soil P dynamics in calcareous systems. Furrow irrigated fields contained more plant‐available P than sprinkler irrigated fields. Furrow irrigation leads to Fe chemistry alterations, release of P, and increases available P. Available P increases under furrow irrigation could limit amendment application based on P, not N, crop needs. We still do not fully understand P dynamics in irrigated calcareous systems.

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Section: Resultsmentioning

confidence: 99%

Mechanisms Responsible for Soil Phosphorus Availability Differences between Sprinkler and Furrow Irrigation

et al. 2019

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“…For example, Hunger et al (2008) found evidence for struvite in poultry litter using XRD patterns to identify crystalline species, and NMR spectroscopy to quantify overall P speciation, but stopped short of performing XANES analyses. Prietzel et al (2016) combined chemical extractions and XANES spectroscopy to investigate P speciation across a variety of soil environments, whereas Helfenstein et al (2018) combined extractions, isotopic analyses, and spectroscopy to quantify P pools in soils. Ajiboye et al (2007) used NMR spectroscopy, chemical extractions, and P K ‐edge XANES analysis to quantify P speciation in organic soil amendments such as manure and biosolids.…”

Section: Discussionmentioning

confidence: 99%

X‐Ray Spectroscopic Quantification of Struvite and Dittmarite Recovered from Wastewater

Massey

2019

J of Env Quality

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Phosphorus recovery from wastewater as struvite (MgNH4PO4⋅6H2O) or dittmarite (MgNH4PO4⋅H2O) can decrease water pollution risk, as well as produce a P‐rich material suitable as fertilizer. However, most studies to date have focused on the removal of P from wastewater, rather than on characterization of the recovered P materials. The objective of this work was to apply microfocused X‐ray fluorescence (XRF) spectroscopy, and both bulk and microfused X‐ray absorption near edge structure (XANES) spectroscopy, to provide insight into the speciation of recovered P in various struvite‐containing and struvite‐like materials. Three materials were investigated: homogeneous crystalline struvite on apatite seed, homogeneous dittmarite, and heterogeneous struvite with sand contamination (referred to as the “sandy” material). The struvite materials were recovered from dairy wastewater, whereas the dittmarite was from a cheese processing plant. Phosphorus speciation in the crystalline struvite on apatite seed material was ∼17% apatite and 83% struvite; in the “sandy” material, P was ∼24% apatite and ∼76% struvite, with an uncertainty of approximately ±15%. The P K‐edge XANES spectra of recovered dittmarite appeared pure. These findings highlight the heterogeneity of recovered P materials and underscore the importance of P speciation to understand P release behavior and bioavailability from recovered phosphates. Core Ideas Multiple methods should be used to corroborate spectroscopic estimates of P speciation. Dittmarite P K‐edge XANES spectra are distinct from spectra of chemically similar struvite. Phosphorus K‐edge XANES spectroscopy can quantify Mg‐associated P >15 atom% P.

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“…Extraction conditions such as the solution‐to‐soil ratio are known to influence the amount of P extracted from soils, but did not affect the δ 18 O P values of Bray‐1 P unf , despite marked changes in P concentrations depending on the extraction conditions. This indicates that the soil P pool extracted via Bray‐1 remains the same, despite the increasing P concentrations, assuming that different P pools have distinct δ 18 O P values . Neither P concentrations nor δ 18 O P values were influenced by extraction temperature, presumably due to the short extraction time.…”

Section: Discussionmentioning

confidence: 97%

“…extraction temperature for AEM 4°C and a δ 18 O value of the water used for the extraction of −4.2‰), but this also seems unlikely. It is possible that the Bray‐1 solution extracts a different pool of inorganic P from that extracted by AEM, with different δ 18 O P values, which would not be detected using 18 O‐labelled and unlabelled solutions. Thus, the differences between the δ 18 O P values of AEM and Bray‐1 P unf might be explained by a combination of differences in P pools and changes during extraction.…”

Section: Discussionmentioning

confidence: 99%

“…A promising technique for the investigation of soil P cycling involves the determination of the 18 O: 16 O ratio of oxygen (O) bound to P (δ 18 O P value). [3][4][5][6] The δ 18 O P technique has been used to investigate the importance of microorganisms for P cycling 7 and can provide information about hydrolysis by phosphatase enzymes 8,9 and the origin of P inputs into aquatic systems. 10,11 However, information on δ 18 O P values in tropical forest soils remains scarce, despite the importance of P in the ecology of this hyper diverse biome.…”

Section: Introductionmentioning

confidence: 99%

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A rapid ammonium fluoride method to determine the oxygen isotope ratio of available phosphorus in tropical soils

Pfahler

Bielnicka

Smith

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale The isotopic composition of oxygen bound to phosphorus (δ18OP value) offers an opportunity to gain insight into P cycling mechanisms. However, there is little information for tropical forest soils, which presents a challenge for δ18OP measurements due to low available P concentrations. Here we report the use of a rapid ammonium fluoride extraction method (Bray‐1) as an alternative to the widely used anion‐exchange membrane (AEM) method for quantification of δ18OP values of available P in tropical forest soils. Methods We compared P concentrations and δ18OP values of available and microbial P determined by AEM and Bray‐1 extraction for a series of tropical forest soils from Panama spanning a steep P gradient. This involved an assessment of the influence of extraction conditions, including temperature, extraction time, fumigation time and solution‐to‐soil ratio, on P concentrations and isotope ratios. Results Depending on the extraction conditions, Bray‐1 P concentrations ranged from 0.2 to 66.3 mg P kg−1 across the soils. Extraction time and temperature had only minor effects on Bray‐1 P, but concentrations increased markedly as the solution‐to‐soil ratio increased. In contrast, extraction conditions did not affect Bray‐1 δ18OP values, indicating that Bray‐1 provides a robust measure of the isotopic composition of available soil P. For a relatively high P soil, available and fumigation‐released (microbial) δ18OP values determined by Bray‐1 extraction (20‰ and 16‰, respectively) were higher than those determined by the AEM method (18‰ and 12‰, respectively), which we attribute to slightly different P pools extracted by the two methods and/or differences resulting from the longer extraction time needed for the AEM method. Conclusions The short extraction time, insensitivity to extraction conditions and smaller mass of soil required to extract sufficient P for isotopic analysis make Bray‐1extraction a suitable alternative to the AEM method for the determination of δ18OP values of available P in tropical soils.

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Combining spectroscopic and isotopic techniques gives a dynamic view of phosphorus cycling in soil

Cited by 171 publications

References 64 publications

Mechanisms Responsible for Soil Phosphorus Availability Differences between Sprinkler and Furrow Irrigation

Mechanisms Responsible for Soil Phosphorus Availability Differences between Sprinkler and Furrow Irrigation

X‐Ray Spectroscopic Quantification of Struvite and Dittmarite Recovered from Wastewater

A rapid ammonium fluoride method to determine the oxygen isotope ratio of available phosphorus in tropical soils

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