Effect of Soil/Solution Ratio on Determining the Chemical Potentials of Phosphate Ions in Soil Solutions

Larsen, S.; Widdowson, A. E.

doi:10.1038/203942a0

Cited by 20 publications

(13 citation statements)

References 6 publications

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“…The soi1:solution ratio greatly influences the partitioning betwen adsorbed P and solution concentration (Larsen & Widdowson, 1964;White, 1966;Hope & Syers, 1976;Barrow & Shaw, 1979). However, conflicting results about the effect of soi1:solution ratio exist.…”

Section: Introductionmentioning

confidence: 93%

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

Chapman¹,

Edwards²,

Shand³

1997

European J Soil Science

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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.

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Section: Introductionmentioning

confidence: 93%

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

Chapman¹,

Edwards²,

Shand³

1997

European J Soil Science

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“…Soil P is at any rate soluble in this more dilute soil solution than it is in the concentrated neutral salt solution. The use of 0.01M CaCk solution is derived from physico-chemical studies on P potential (Aslyng, 1954;Schofield, 1955;Larsen and Court, 1960).…”

Section: Simonis and Setatoumentioning

confidence: 99%

Assessment of available phosphorus and potassium in soils by the calcium chloride extraction method

Simonis¹,

Setatou²

1996

Communications in Soil Science and Plant Analysis

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The availability of phosphorus (P) and potassium (K) of 30 soils representative of the main great soil groups of northern Greece was estimated by the 0.01M CaCl 2 extraction method, and the values obtained were correlated with short-and long-term uptake and dry matter yields of ryegrass grown in pots as well as with the soil Olsen-P and NH 4 OAc-K values. Coefficients of correlation for P and K values of soils with total P uptake of six cuttings and K uptake of ten cuttings were calculated for groups of soils, classified on the basis of pH, texture, cation exchange capacity, and percent base saturation. The amounts of P extracted by 0.01M CaCl 2 solution were extremely small, ranging from 0.15 to 1.50 ppm P and in certain cases lead to considerable analytical difficulties. The correlations between P and K obtained by ryegrass and P and K values determined by the 0.01M CaCl 2 method were statistically significant (r = 0.

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“…Over longer periods (e.g. 16 hr, as used by Larsen and Widdowson 1964) the effects of initial soil phosphate disequilibrium and of microbial activity in the suspensions are likely to be confounded.…”

Section: Discussionmentioning

confidence: 99%

“…Various workers (Aslyng 1954(Aslyng , 1964Wild 1959;Larsen and Court 1960;Larsen and Widdowson 1964) suggest that the value of the phosphate potential of a soil depends on the soil/solution ratio, the potentialt decreasing as the concentration of the soil suspension increases. These authors measured the phosphate concentration in solution after shaking a soil with a solution containing no phosphate initially.…”

Section: Introductionmentioning

confidence: 99%

Studies on the Phosphate Potentials of Soils IV The mechanism of the 'soil/solution ratio effect'

White¹

1966

Soil Res.

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The equilibrium phosphate potentialSP and the slope of the quantity/intensity (Q/I) relation of three contrasted soils increased as the soil/solution ratio was decreased from 115 to 1/50. On allowing the soil phosphate to achieve equilibrium by prolonged storage under constant environmental conditions, the equilibrium potentialSP and the slope dQ/dI remained constant and independent of the soil/solution ratio. The 'soil/solution ratio effect' is interpreted in terms of phosphate disequilibrium, a condition common in soils in situ, which can be due to either non-uniform removal of phosphate or to non-uniform distribution of soluble phosphate recently added to the soil. The two kinds of disequilibrium cannot be distinguished by their observed soil/solution ratio effects, but may be identified by the direction of change of the potentialsp on the attainment of equilibrium in the soil. PotentialSP values measured in initially phosphate-free solutions are discussed with reference to their dependence on the soil/solution ratio. Aslyng's method of extrapolating to 'zero dilution' gives a reasonably accurate measure of the true potentialSP of an 'equilibrium' soil, but is in error for a 'disequilibrium' soil. It is suggested that the equilibrium potentialSP determined at a 1/50 (or smaller) soil/solution ratio will provide an adequate measure of the mean potentialSP of a disequilibrium soil.

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Effect of Soil/Solution Ratio on Determining the Chemical Potentials of Phosphate Ions in Soil Solutions

Cited by 20 publications

References 6 publications

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

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

Assessment of available phosphorus and potassium in soils by the calcium chloride extraction method

Studies on the Phosphate Potentials of Soils IV The mechanism of the 'soil/solution ratio effect'

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