Nature and distribution of soil phosphorus as revealed by a sequential extraction method followed by ³¹P nuclear magnetic resonance analysis

Abstract

Soil samples from long-term plots annually fertilized with superphosphate since 1952 and also unfertilized (control) plots of an irrigated and intensively grazed pasture in Canterbury, New Zealand, were subjected to a sequential extraction procedure followed by "P nuclear magnetic resonance (NMR) analysis of the soil phosphorus (P) forms present.Overall, 80% of the total organic P (as determined by ignition) was removed from the soil by the sequential extraction procedure. Most of the organic P (900/) detected by NMR was in the monoester fraction. Small quantities of diester and pyrophosphate were also found. Choline phosphate constituted a significant proportion (18-25%) of the monoester P in the acetylacetone and 0.5 M NaOH extracts. Long-term superphosphate additions resulted in almost all of the P accumulated in the monoester P fraction (up to 99Yo).

Phosphorus fractions in soil with a long history of organic waste and mineral fertilizer addition

“…In general, the lowest inorganic and organic contents extracted by AER and NaHCO 3 were observed in the control soil without fertilization, especially at the 0.0 -0.12-m layer. The inorganic fraction extracted by NaHCO 3 is considered as an available form because it is balanced with the P of the soil solution (Condron et al 1985;Guardini et al 2012). The organic fraction extracted with NaHCO 3 , despite being contained in organic compounds and therefore considered at first unavailable, is an easily decomposable form formed by diester phosphates and regulated by the soil microbial activity (Chen et al 2002;Xavier et al 2009).…”

Biodisponibilidade de formas de fósforo acumuladas em solo sob sistema plantio direto

“…Com as modificações propostas por Condron et al (1985), os extratores utilizados no fracionamento são, seqüencialmente, resina trocadora de ânions (Pi RTA ), NaHCO 3 0,5 mol L -1 a pH 8,5 (Pi bic e Po bic ), NaOH 0,1 mol L -1 (Pi hid e Po hid ), HCl 1,0 mol L -1 (Pi HCl ), NaOH 0,5 mol L -1 (Pi hid0,5 e Po hid0,5 ) e digestão com H 2 SO 4 + H 2 O 2 + MgCl 2 (P residual ). As frações orgânicas (Po) são determinadas pela diferença entre o P total e o Pi em cada extrator.…”

Phosphorus fractions in soil after successive crops of Pinus taeda L. without fertilization

“…Phosphorus was chemically fractionated according to HEDLEY et al (1982), modified according to CONDRON et al (1985), as follows: samples of 0.5g dry soil were subjected to sequential extraction with anion-exchange resin (AER-Pi); NaHCO 3 0.5mol L -1 (NaHCO 3 -Pi and NaHCO 3 -Po); HCl 1.0mol L -1 (HCl-Pi) and NaOH 0.5mol L -1 + ultrasound (NaOH-Pi and NaOH-Po). After the extractions, the remaining soil was oven-dried and subjected to digestion with H 2 SO 4 + H 2 O 2 + MgCl 2 (Residual-P).…”