XANES Speciation of Phosphorus in Organically Amended and Fertilized Vertisol and Mollisol

Abstract

Knowledge of the dominant P species present in the soil following the application of organic amendments and fertilizer is important in understanding the fate of P in the environment. This study was performed to identify P species in two calcareous soils, an Osborne series (Typic Humicryert) and a Lakeland series (Typic Calciudoll), treated with organic amendments (biosolids and hog and dairy cattle manure) and fertilizer (monoammonium phosphate, MAP). Phosphorus 1s x‐ray absorption near‐edge structure (XANES) spectroscopy was used to speciate P compounds in these amended soils. The result showed that “adsorbed P” was the dominant P species in both soils. For the Osborne soil, the unamended soil (control) and those amended with biosolids and MAP contained an appreciable amount of hydroxyapatite (HAP), the most thermodynamically favored Ca phosphate. In addition, soils amended with biosolids or hog or dairy manures contain β‐tricalcium phosphate (TRICAL), a more soluble form of Ca phosphate than HAP. The amended Lakeland soils contained a variety of species in addition to the dominant “adsorbed P.” While TRICAL was found in all the amended soils except in that amended with hog manure, HAP was present in appreciable amount only in the unamended soil. Overall, the adsorbed P, most likely through inner‐sphere complexation, in these amended soils may not be readily available as a source of P into the environment. In addition, the HAP and TRICAL will have limited solubility, and thus, are probably only a very minor source of P in the environment.

Molecular Speciation of Phosphorus Present in Readily Dispersible Colloids from Agricultural Soils

“…However, XANES LCF analysis did not reveal any P o species in either investigated colloidal sample (Fig. 1), probably because they were below the detection limit of XANES spectroscopy or due to a lack of distinctive spectral features of P o compounds (Beauchemin et al, 2003;Ajiboye et al, 2008;Kruse and Leinweber, 2008). As such, analysis with solution P-NMR was required to provide molecular speciation information about the P pool colorimetrically classified as MUP.…”

“…Synchrotron-based P K-edge XANES spectroscopy provides an extraordinarily valuable method to investigate the solid-phase species of P in heterogeneous samples such as soils (Ajiboye et al, 2008;Beauchemin et al, 2003;Kizewski et al, 2011), sediments (Giguet-Covex et al, 2013), and wastes (Toor et al, 2006). This technique is a nondestructive molecular probe for P speciation and is especially efficient for inorganic P (P i ) forms with unique spectral fingerprints.…”

The chemical nature of P accumulation in agricultural soils—implications for fertiliser management and design: an Australian perspective

“…An earlier and more detailed study by Beauchemin et al (2003) using adsorbed P and mineral P standards confirmed that hydroxyapatite and octocalcium phosphate can indeed be identified in soils. In their soils, these two compounds comprised up to 85% of the total P. Hence, despite some reports asserting that P precipitation is not an important process in controlling P availability and hence fertiliser efficiency (Syers et al 2008), recent direct spectroscopic evidence suggests the opposite (Beauchemin et al 2003;Lombi et al 2006;Ajiboye et al 2008). …”

Nutrient Availability to Corn From Dairy Manures and Fertilizer in a Calcareous Soil

“…In addition, both the manure and compost contained Fe, which could form Fe phosphates, thereby reducing P solubility. Ajiboye et al (2008) found that calcareous soils amended with dairy manure had significant amounts of strengite (FePO 4 ) formation, whereas these same soils treated with MAP did not.…”