The use of rate equations for a quantitative description of K desorption from soils in an external electric field (electro‐ultrafiltration)

Abstract

summpry--ldepwngIons can be extracted from soils by applying an external electric field to a soil suspension. When a constant field strength is employed characteristic desorption parameters can be calculated from the results, such as maximum desorbable quantity, halftime, and rate constant. The method consists of a combination of electrodialysis and ultrafiltration and is called electro-ultrafiltration (EUF).It was found that the K transfer from the central compartment A to the cathode compartment B follows a first order rate law, if compartment A contains only the solution of a strong electrolyte such as KCI. If a soil suspension is introduced into compartment A the bulk of K that is transferred to compartment B has first to be desorbed from the soil particles hence the designation as desorption for the transfer from a soil suspension. In this case a second order rate law is followed.The rate equations allow the calculation of the quantity of K involved in the desorption process and the rate with which it is released. It was found that invariably only the exchangeable K takes part in the desorption reaction. The desorption rate differs between soils and depends on clay content and the quantity of exchangeable K present in the soil. It is suggested that the desorption data may provide a means of describing the soil K status by kinetic parameters. Die Anwendung von

A new approach to quantify the utilization of non-exchangeable soil potassium by plants

“…In order to determine the amount released at infinite time, the experimental data were fitted to a second order rate equation using the transformation suggested by Grimme (1979): In order to determine the amount released at infinite time, the experimental data were fitted to a second order rate equation using the transformation suggested by Grimme (1979):…”

Evaluation of the electro-ultrafiltration technique (EUF) as a measure of the K supplying power of Quebec soils

“…The positive value of the clay content coefficient in the regression equation indicates that for a given amount of K desorbed by EUF (EUF-80) the amount of plant-available K will be larger for fine-textured soils. Grimme (1979) has shown that EUF desorbs K more slowly from soils with high clay contents thus underestimating the amount of 'plant-available K'. Comparable observations were made on the soils used in the present study (Fig.…”

Mobility of potassium and phosphorus in soil as determined by electro‐ultrafiltration (EUF)

“…By trying to fit data to various integrated rate equations, it is possible to verify that the nutrient desorption may be described by a rate equation of zero or second order depending on the form and concentration of reactant in soil (2)(3)(4)(5).…”

“…BUFO, AND PIZZIGALLO, AND BUONDONNA because it not only yields extractable amounts of nutrients from soil but also provides information on the rates with which these quantities are desorbed when an external force is applied (2).…”