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X-ray absorption near edge structure spectroscopy reveals phosphate minerals at surface and agronomic sampling depths in agricultural Ultisols saturated with legacy phosphorus
Citation:
Lucas, E., L. Mosesso, T. Roswall, Y. Yang, K. Scheckel, A. Shober, AND G. Toor. X-ray absorption near edge structure spectroscopy reveals phosphate minerals at surface and agronomic sampling depths in agricultural Ultisols saturated with legacy phosphorus. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 308 part 2:136288, (2022). https://doi.org/10.1016/j.chemosphere.2022.136288
Impact/Purpose:
Knowing the P forms in legacy P soils clarifies how P is stored and the potential for the future release of P to crops and surface waters. Recent long-term studies observed an initial decline of WEP after P applications ceased, followed by a plateau effect, whereby the rate of decline significantly decreased. This decline and plateau occurred at different timescales in these studies (Dodd and Sharpley 2016, Lucas et al. 2021, McDowell et al. 2020), but the pattern was similar, meaning 157 that as the labile pool of P was exhausted, P became available from other pools. Our previous work in the Mid-Atlantic US soils treated with manure P at four different rates exhibited treatment effects with no significant declines in WEP, at 0.2–0.4 mg kg-1 decrease per year, from 9 to 15 years following cessation of P application after an initial decline from years 0 to 9 (Lucas et al. 2021). In the 0–5 cm layer of the same soils discussed in this study, Roswall et al. (2021) attempted to exhaust the WEP pool by conducting sequential water extractions equivalent to a 1:800 soil-to-water ratio; however, by the end of the final extraction, the remaining WEP pool was still higher than the US EPA recommended limit for regional streams and rivers (0.03125 mg L-1). Speciation of P using XANES may help to explain the legacy P storage mechanisms in these soils. Our objective in this study was to identify various dominant P forms in the surface (0–5 cm) and agronomic layers (0–20 cm) of selected Mid-Atlantic Ultisols that may contribute to environmentally and agronomically available P pools, and potentially impact water quality.
Description:
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.
URLs/Downloads:
DOI: X-ray absorption near edge structure spectroscopy reveals phosphate minerals at surface and agronomic sampling depths in agricultural Ultisols saturated with legacy phosphorus
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