The wedge belt refers to the area where the hydration and depotification of the mica sheet is gradually advanced from the edge to the center, and the edge of the sheet is wedge-shaped. During the release of potassium, the edge of the particles containing potassium minerals first expands, causing the edge layer of the particles to gradually open, and then the edge is broken to form a wedge-shaped strip. The wedge-shaped strip increases with the opening of the layer and decreases with the opening of the layer. The K+ in the wedge-shaped region of the mica-based mineral weathering edge can be exchanged by H+ or NHf, but cannot be exchanged by ions with large hydration radii such as Ca2+ and Mg.
K+ in the wedge-shaped region is part of the exchangeable potassium in the soil. Once the wedge mineral region is formed on the edge of the clay mineral, the fixed strength of the exogenous potassium is increased. The wedge-shaped region can be formed during the de-potassium weathering process of the mica, or can be formed by causing the crystal layer to be unevenly contracted after the potassium ion or the ammonium ion in the soil solution enters the complex three-square mesh between the expansive mineral layers. In addition, after the lime is applied to raise the pH of the acidic soil, the loss of the polymerized hydroxyaluminum between the mineral layers causes the crystal layer to collapse, and a wedge-shaped region may also be formed.