Microscale Heterogeneous Distribution and Speciation of Phosphorus in Soils Amended with Mineral Fertilizer and Cattle Manure Compost

Abstract

Global concerns for the sustainability of agriculture have emphasized the need to reduce the use of mineral fertilizer. Although phosphorus (P) is accumulated in farmland soils due to the long-term application of fertilizer, most soil P is not readily available to plants. The chemical speciation of P in soils, which comprise heterogeneous microenvironments, cannot be evaluated with a high degree of specificity using only macroscopic analyses. In this study, we investigated the distribution and speciation of P accumulated in soils by using both macro- and microscopic techniques including chemical extraction, solution and solid-state 31P NMR, bulk- and micro- P K-edge X-ray absorption near edge structure (XANES), and electron probe microanalysis (EPMA). Soil samples were collected from a field in which cabbage was cultivated under three amendment treatments: i) mineral fertilizer (NPK), ii) mineral fertilizer and compost (NPK + compost), and iii) mineral fertilizer plus compost but without nitrogen fertilizer (PK + compost). Macro-scale analyses suggested that accumulated P was predominantly inorganic P and associated with Al-bearing minerals. The repeated application of compost to the soils increased the proportion of P associated with Ca which accounted for 17% in the NPK + compost plot and 40% in the PK + compost plot. At the microscale, hot spots of P were heterogeneously distributed, and P was associated with Fe and Ca in hot spots of the NPK + compost (pH 6) and PK + compost (pH 7) treated samples, respectively. Our results indicate that application of compost contributed to creating diverse microenvironments hosting P in these soils.

Phosphate binding to allophane and ferrihydrite with implications for volcanic ash soils

“…A large portion of PO 4 was found in the NH 4 F extract across all soils, accounting for 63–78% of the sum of PO 4 in the extracts. Phosphate extracted by the NH 4 F solution is considered as PO 4 associated with Al bearing phases (Yamaguchi et al., 2021). In contrast, PO 4 in the NaOH fraction, which presumably extracts PO 4 associated with soil Fe, was minor, with less than 29% of the sum of PO 4 in the extracts.…”

“…Phosphorus K-edge XANES spectra for phosphate bound to 3d transition metals exhibit a distinctive pre-edge feature at the low-energy side of the white line around 2,150 eV (Okude et al, 1999). This feature has been successfully used to qualitatively and quantitatively distinguish phosphate associated with Fe vs. Al in soils (Takamoto et al, 2021;Yamaguchi et al, 2021;Yamamoto & Hashimoto, 2017;Yamamoto et al, 2018) and in synthesized Al-or Fe-oxide systems (Khare et al, 2004(Khare et al, , 2005Liu & Hesterberg, 2011). Taking advantage of the elemental specificity of XANES spectroscopy, Khare et al (2004Khare et al ( , 2005 determined the distribution of phosphate between Al and Fe in mixed compound systems at different phosphate concentrations and pH values.…”

Significance of phosphorus inclusions and discrete micron‐sized grains of apatite in postglacial forest soils

“…This shows that the Ca concentration at these spots increased with increasing P concentrations by 2.8-fold (Figure 4). An observation that is common in most high-resolution microscale studies of P is that the P abundance is not evenly distributed in soils, as there are commonly unique spots of high P intensities even at the microscale (Adediran et al, 2020;Hesterberg et al, 2017;Vogel et al, 2021;Werner, Mueller, et al, 2017;Yamaguchi et al, 2021). The significance of spatial heterogeneity in the concentrations of P at the microscale is, however, understudied.…”

“…The use of synchrotron‐based X‐ray fluorescence (μ‐XRF) microscopy in combination with micro‐focused P K ‐edge X‐ray absorption near edge structure (XANES) spectroscopy is gaining attention and allows for spatially resolved P chemical speciation in soils at the microscale (Hesterberg et al, 2017; Werner, Mueller, et al, 2017; Yamaguchi et al, 2021). Synchrotron P K ‐edge micro‐spectroscopy was recently used to reveal P hot spots and dust‐derived apatite grains in acidic, highly weathered Hawaiian soils (Vogel et al, 2021).…”

Soft X-ray Fluorescence and Near-Edge Absorption Microscopy for Investigating Metabolic Features in Biological Systems: A Review

“…Currently, the metabolic processes which take place in the soil can completely change pathways depending on soil chemical and mineralogical properties and, thus, depending on the application of organic or inorganic amendment [ 35 ].…”