The phosphorus composition of soil solutions and soil leachates: Influence of soil:solution ratio

Abstract

Compositional differences between soil solutions obtained by different methods have frequently been reported; variations in the soi1:solution ratio may explain these results. In this study we compared the amount and composition of phosphorus (P) in soil leachates and soil solutions from a temperate grassland soil in northeast Scotland and determined the influence of soi1:solution ratio on P fractions in soil water extracts. Leachates were collected from intact soil cores over 6 months, the cores were then destructively sampled, and soil solutions obtained by centrifuging. Molybdate reactive P (MRP) represented 71% of the total dissolved P (TDP) in soil leachates but only 54% in soil solutions. The MRP component in soil water extracts increased from 71% to 92% as the soi1:solution ratio increased from 1 : l S to 1:15.4, while the dissolved organic P (DOP) component decreased from 26% to 6%. As the soiholution ratio increased the amount of MRP extracted increased; by contrast the amount of DOP and dissolved condensed P (DCP) extracted remained constant. While the MRP component is regulated by soil sorption processes, the supply and amount of DOP and DCP is probably related to biological activity. Dissolved organic carbon (DOC) extracted at wide soi1:solution ratios contained a smaller proportion of P than that extracted at narrower ratios. The results indicate differences in the behaviour of P fractions in the soil at various soi1:solution ratios and that these are reflected in the P composition of soil solution and leachate.

Laboratory drying of organic-matter rich soils: Phosphorus solubility effects, influence of soil characteristics, and consequences for environmental interpretation

“…However, expressed on a soil-weight basis, mineral-soil P w MUP increases noted here (averaging 10.13mg P kg − 1 ) were considerably greater than increases reported for UK lowland pasture soils by Turner and Haygarth (2001) (< 1 to 5.5mg P kg − 1 ) and for 2 Australian pasture soils as reported by (1.17 and 0.62mg P kg − 1 ). Chapman et al (1997a) found that the soil/water ratio used in P w analyses had little effect on the quantity of P w MUP extracted. Comparatively high P w MUP increases in this study therefore indicate that Irish grassland soils contain particularly large quantities of organic and fine colloidal P susceptible to dryinginduced solubilisation.…”

Overview of Selected Soil Pore Water Extraction Methods for the Determination of Potentially Toxic Elements in Contaminated Soils: Operational and Technical Aspects

“…Menzies and Bell, 1988;Zabowski and Ugolini, 1990;Sheppard et al, 1992;Dahlgren, 1993;Lorenz et al, 1994;Giesler et al, 1996;Chapman et al, 1997). Most studies are fairly consistent in their illustration of the differences among methods in terms of element concentrations in pore water, partly due to different fractions of pore waters considered.…”

Chemical Speciation in Soils and Related Materials by Selective Chemical Extraction

“…Extraction procedures have also been developed for the determination of the anionic species in soils of elements such as sulfur which are important as binding sites for metals as well as for its own mobility and availability (Cordos et al, 1995). The important biosignificant element selenium has similarly received attention (Blaylock and James 1993;Seby et al, 1997) and procedures for the speciation of phosphorus have been developed (Vaz et al, 1992;Chapman et al, 1997).…”