The composition of organic phosphorus in soils of the Snowy Mountains region of south-eastern Australia

Abstract

Abstract. Few studies have considered the influence of climate on organic phosphorus (P) speciation in soils. We used sodium hydroxide-ethylenediaminetetra-acetic acid (NaOH-EDTA) soil extractions and solution 31 P nuclear magnetic resonance spectroscopy to investigate the soil P composition of five alpine and sub-alpine soils. The aim was to compare the P speciation of this set of soils with those of soils typically reported in the literature from other cold and wet locations, as well as those of other Australian soils from warmer and drier environments. For all alpine and sub-alpine soils, the majority of P detected was in an organic form (54-66% of total NaOH-EDTA extractable P). Phosphomonoesters comprised the largest pool of extractable organic P (83-100%) with prominent peaks assigned to myo-and scyllo-inositol hexakisphosphate (IP 6 ), although trace amounts of the neo-and D-chiro-IP 6 stereoisomers were also present. Phosphonates were identified in the soils from the coldest and wettest locations; a-and b-glycerophosphate and mononucleotides were minor components of organic P in all soils. The composition of organic P in these soils contrasts with that reported previously for Australian soils from warm, dry environments where inositol phosphate (IP 6 ) peaks were less dominant or absent and humic-P and a-and b-glycerophosphate were proportionally larger components of organic P. Instead, the soil organic P composition exhibited similarities to soils from other cold, wet environments. This provides preliminary evidence that climate is a key driver in the variation of organic P speciation in soils.

Characterization of Phosphorus in Subtropical Coastal Sand Dune Forest Soils

“…This new technique was suggested for use in future applications of 31 P-NMR spectroscopy. Overall, the proportions of P i and P o evaluated by sequential chemical extraction and 31 P-NMR spectroscopy were mostly consistent in this study and the results were similar to those from other studies [28,46,58].…”

“…Overall, the peak values of inorganic orthophosphate, pyrophosphate, and orthophosphate monoesters and diesters determined by 31 P-NMR were similar or identical to previous findings [17,20,51]. The peak signal positioned around 4.5 ppm was myo-inositol hexakisphosphate [11,52,53] and the peak signal centered at −0.5 ppm was DNA [14,46]. Myo-inositol hexakisphosphate and DNA represented the dominant forms of orthophosphate monoesters and diesters, respectively, in this study.…”

“…Sufficient moisture under warm climates increases the rate of microbial decomposition, which makes organic matter decompose rapidly [46], so a smaller amount of organic matter accumulated in the mineral-II layer in our site. Because the recalcitrant P i forms did not easily decompose, most of the HCl-P i and cHCl-P content accumulated in the mineral-II soils.…”

The chemical nature of organic phosphorus that accumulates in fertilized soils of a temperate pasture as determined by solution 31P NMR spectroscopy

“…This would infer that the synthesis of broad phosphomonoesters is occurring outside the plant cell. In any case, the role of climate and microorganisms appear to be related to the relative amounts of broad phosphomonoesters ( Doolette et al, 2016; Moata et al, 2016). Further research is needed to identify the processes responsible for the sequestration of broad phosphomonoesters.…”

“…However, in soils that are saturated with P, we expect that the rate limiting steps on the sequestration of organic P will also be that related to plant growth and microbial activity, i.e. , the influence of climate ( Tamburini et al, 2012; Doolette et al, 2016).…”