Potassium Release Rate Research Articles

Muscovite dissolution kinetics as a function of pH and time at 70°C

The dissolution rate of muscovite at 70°C was determined using a single-pass, flow-through apparatus. Dissolution rate data were obtained at approximately unit pH interval over the pH range 1.4 to 11.8 in 11 separate experiments, each lasting 50 days. The muscovite dissolution rates were defined by the silica, aluminum and/or potassium release rates to solution. Under most pH conditions the dissolution at steady-state was congruent or nearly so. Speciation-solubility calculations made using the geochemical modeling code EQ3NR indicate that the fluids were maintained far from equilibrium with respect to muscovite and undersaturated with respect to possible secondary minerals.Under all pH conditions we initially observe a transiently elevated dissolution rate. The dissolution rate gradually approaches a limiting (steady-state) value, which we interpret as the dissolution rate of the bulk mineral. From pH 1 to approximately pH 5, the limiting rate for muscovite dissolution at 70°C varies negatively with pH, and the rate constant, k, is 10−14.7 mol/cm2 · s. Under acidic conditions the dissolution rate is proportional to−0.37 pH. As pH is increased at 70°C, the rate of dissolution becomes essentially pH independent, and k is 10−16.6 mol/cm2 · s. At about pH 7 and higher the limiting rate for muscovite dissolution varies positively with hydroxyl ion activity, and the dissolution rate is proportional to +0.22 pH. Under alkaline conditions k is 10−18.1 mol/cm 2 · s at 70°C.

ECTOMYCORRHIZAS AFFECT IONIC BALANCE DURING AMMONIUM UPTAKE BY DOUGLAS‐FIR ROOTS

SUMMARYMycorrhizas have been shown to alter ion fluxes for many nutrients. Experiments were done to determine the extent to which ectomycorrhizas alter the ionic balance of roots of Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings mycorrhizal with Hebeloma crustuliniforme (Bull, ex St. Amans) Qúel. exposed to solutions containing either 16N ammonium sulphate or 16N ammonium chloride. Net fluxes of ammonium, hydrogen, potassium, calcium, sodium, bicarbonate, sulphate and chloride were measured. The mycorrhizal association altered ion fluxes, primarily decreasing sodium uptake and potassium release rates (both anion treatments) and increasing bicarbonate release during exposure to ammonium chloride. Rates of carboxylate accumulation in the tissue were inferred from the net flux data; mycorrhizal seedlings may produce more cation‐carboxylate complexes compared with nonmycorrhizal seedlings. When compared with agricultural plants exposed to ammonium, Douglas‐fir took up a considerably greater number of cations for each ammonium ion absorbed, which may account for the greater number of carboxylate anions also produced by Douglas‐fir. These findings were discussed in terms of ecological significance for growth of Douglas‐fir.

Potassium release from selected slow‐release fertilizers

Abstract Potassium (K) release rate from Osmocote 14–6.3–11.6 (N‐P‐k), MagAmp 7–18–5, Choice 10–4.3–8.3, Scotts 21–3–5.8 and Unimix 10–8.7–4.2 was determined. During the 63‐day experiment Osmocote and Scotts had relatively linear release rates while the release rate from the other fertilizers was initially rapid and decreased over time.

A technique for determining potassium release from a slow‐release fertilizer

Abstract A new technique was utilized to determine the rate of potassium release from a slow‐release fertilizer. The technique is based on diffusion of the potassium ion into a saturated capillary mat followed by extraction and analysis of the solution pressed from the capillary mat. The technique demonstrated that K was released at a rate similar to that reported by another researcher. The major advantage of this technique is the simple readily available equipment needed for solution extraction.

Veränderungen von Dreischicht‐Tonmineralen durch natives K in holozänen Lößböden Mitteldeutschlands und Niederbayerns

Changes of three‐layer clay minerals by native K in holocene loess derived soils of Central Germany and Lower Bavaria.Transformations of the clay minerals illite, vermiculite and smectite were determined in Central German (31 profiles) and Lower Bavarian loess districts (5 profiles) using 31–36 soil properties. To get significant differences between solum and sediment, the multivariate diskriminant analysis was applied.In the Central German loess district the following properties were crucial, to receive significant separation between solum‐horizons and sediments: smectite content, several values of potassium fixation, interlattice potassium. Important were also some parameter of the K‐Ca‐exchange curve: Activity ratio \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{{\rm aK}}}{{\sqrt {{\rm aCa}}}}} \right) $\end{document} of a soil solution in equilibrium with a soil (ARo), buffering capacity of the soil for K at equilibrium (BCKE), labile K(K1), exchange capacity of the exchange sites with a specific affinity for K minus labile K(ECx—K1). The differences of these values can be explained by assuming that (at pH 6–7) the beidellitic layers of smectites of the parent loess were transformed to illitic layers in the solum‐horizons.In the Lower Bavarian loess landscape potassium fixation, total K in clay fraction (< 2 μm) and the parameters of the K‐Ca‐exchange curve indicate the same clay mineral transformation as in Central Germany. Smectite values were not introduced to the diskriminant function, because they were highly significantly correlated with potassium fixation. In this case potassium fixation has caused a better separation between the solum‐horizons and the parent loess than X‐ray data.From these results, from total ‐K of the fraction 2–20μm (solum‐horizons smaller than sediments) and the vermiculite content fo the clay fraction, it can be concluded, that the rate of potassium release from micas and the rate of potassium fixation by beidellitic sheets during the Holocene period were nearly equal.

Kaliumabgabe der isolierten Rattenleber nach Applikation von Evans Blau

1. Evans Blue (20 mg/40 ml) causes a potassium release of 59 ± 10 μVal/g in 30 min in isolated rat livers, which were perfused with red cell-free and albumin-free solutions. This effect is not observed in the presence of albumin. 2. When the perfusion medium was exchanged after the potassium release with a solution containing 3% albumin, the liver takes up 77 ± 10% of the released potassium in 90 min. 3. The rate of potassium release caused by Evans Blue is not changed by a decrease of temperature from 27° to 10°C. This is in contrast to the highly temperature dependent potassium release of the phalloidin poisoned liver. 4. Low doses of Evans Blue (0.5–1 mg) inhibit the effects of phalloidin on the liver in vitro. 5. Evans Blue protects mice against the lethal effect of phalloidin in vivo. Protecting doses show an inhibitory effect on the Indocyanine green uptake of the liver in vivo.

Differential Release of Potassium from Interstratified Mica Clay Minerals as Related to Probable Differences in Their Mica Layer Components

AbstractRelease of potassium by extraction with solutions containing sodium tetraphenyl boron or by leaching with 0·1 N barium chloride seemed to be related to the nature of the mica layers in the interstratified minerals studied. The rate of potassium release was lower when the calculated Si/AlIV ratio of the mica component layers resembled muscovite and higher when this ratio was intermediate between muscovite and pyrophyllite. This supported a recent hypothesis that the composition and structure of the mica component layers may vary in different interstratified minerals of similar total chemical composition.

Rate of Potassium Release from Fixed and Native Forms

AbstractThe rate of release of K from fixed and native forms was compared utilizing a biotite‐vermiculite system. Although X‐ray diffraction patterns of oriented aggregates showed little difference between native biotite and weathered biotite containing fixed K, there was a marked difference in the rates of K release from the two materials. The release from native biotite was maintained at nearly a constant rate while approximately 50% of the K was removed, whereas with the fixed forms, rate of release decreased with time. The relationship between the logarithm of the rate of release and time was linear. The slopes of these curves were directly related to the extent of weathering which the weathered biotite had undergone before being subjected to the fixation reaction. The ease of release of fixed K therefore appears to be a function of the extent of weathering of the mica. This may be the result of loss of charge in the mineral during weathering.