SOURCES OF ERROR IN THE DETERMINATION OF SOIL POTASSIUM ACTIVITY RATIOS BY THE <i>Q/I</i> PROCEDURE

Moss, P.; Beckett, P. H. T.

doi:10.1111/j.1365-2389.1971.tb01635.x

Cited by 9 publications

(3 citation statements)

References 51 publications

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“…They calculated the change in the amount of NEK by the difference between AKi-f measured at one time and AKi-f of a so-called 'instantaneous' Q/1 curve, assuming that only negligible release or fixation occurred during the short course of the 'instantaneous' Q/r experiment. Moss & Beckett (1971), however, noticed that the shaking period must not be too long so as to avoid release and that a significant fixation can occur during a period as short as 30 min. Thus, Matthews & Beckett's method can provide biased underestimated results.…”

Section: Discussion On Methodologymentioning

confidence: 95%

“…The proposed calculation of the contribution of EK and NEK to the K balance of the soil-solution system is accurate as far as the choice of the initial exchangeable potassium (E,) is appropriate. Under certain conditions, as discussed by Moss & Beckett (1971), the activity ratio ARo for which neither sorption nor desorption occurs can be considered as the equilibrium activity ratio of the soil in its initial moisture state before the contact with the solution. If this is the case then the soil in its initial moisture state and the soil in equilibrium with a solution of composition ARo should have the same EK value.…”

Section: Discussion On Methodologymentioning

confidence: 99%

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Release and fixation of potassium by a loamy soil as affected by initial water content and potassium status of soil samples

Schneider¹

1997

European J Soil Science

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To understand the contribution of nonexchangeable potassium to plant nutrition the release and fixation of K was studied on a range of soil samples of varying K status, obtained from a long-term fertilizer trial. The soil samples were either air-dried or not prior to use so as to determine the influence of pretreatment on release and fixation of K. Sorption and desorption of K were measured by following the changes in solution K and exchangeable K, and calculating the relative contributions of exchangeable and nonexchangeable K to K dynamics in the soil-solution systems. The change in the amount of nonexchangeable K is proportional to the difference between the initially imposed concentration and the concentration for which neither sorption nor desorption occurred. Whether release or fixation occurs depends on the sign of this difference. Soils containing much K release more K than those containing little K at the same initial or final concentration in solution. The threshold exchangeable potassium and the threshold K concentration for which release becomes large increase when K content increases in the soil. For air-dried soils K-enriched soils fixed less K than those containing little K. But when kept moist the soils fixed no K. The threshold exchangeable potassium of release and the minimal exchangeable potassium, i.e. that part of exchangeable potassium extracted by ammonium acetate but which is not in exchange equilibrium with Ca, are useful criteria to assess the meaning of the exchangeable potassium when used as a fertility indicator.

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Section: Discussion On Methodologymentioning

confidence: 95%

Section: Discussion On Methodologymentioning

confidence: 99%

Release and fixation of potassium by a loamy soil as affected by initial water content and potassium status of soil samples

Schneider¹

1997

European J Soil Science

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“…(37)], and the quantity-intensity (Q/I) technique presented by Matthews and Beckett (1962) have been used mostly to describe K + cation availability in soils (Beckett, 1964;Moss and Beckett, 1971). The quantity of exchangeable K + in the soil (L\K) is plotted as a function ofthe intensity factor, or activity ratio (ARK), where ARK = aK/Jaca + aMg, and ai = activity of cation i.…”

Section: {Sb L/2 }(A+)mentioning

confidence: 99%

Equilibrium-Based Modeling of Chemical Sorption on Soils and Soil Constituents

Schulthess¹,

Sparks²

1991

Advances in Soil Science

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Distribution of roots, water and nutrients beneath cabbage grown in the field

Goodman¹,

Greenwood²

1976

J Sci Food Agric

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Detailed measurements were made of the distributions of roots, water, nitrate, potassium and magnesium in the soil beneath summer cabbage that had been grown in the field for various periods of time. With few exceptions the concentration of water and nutrients did not vary with horizontal distance; the only detectable trends were in the concentrations of nitrate and potassium in the surface layer beneath large plants but these trends were much less than those of rooting density. The vertical distributions of nitrate and potassium ions were largely determined by rainfall which resulted in much loss of nitrate from the root zone and movement of potassium down the profile. Removal of water by evapotranspiration was more or less uniform down the profile despite rooting density declining sharply with depth. The significance of these findings to computer simulation of water and nutrient uptake by plants is discussed.

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SOURCES OF ERROR IN THE DETERMINATION OF SOIL POTASSIUM ACTIVITY RATIOS BY THE Q/I PROCEDURE

Cited by 9 publications

References 51 publications

Release and fixation of potassium by a loamy soil as affected by initial water content and potassium status of soil samples

Release and fixation of potassium by a loamy soil as affected by initial water content and potassium status of soil samples

Equilibrium-Based Modeling of Chemical Sorption on Soils and Soil Constituents

Distribution of roots, water and nutrients beneath cabbage grown in the field

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