Potassium Fixation occurs when which of the following clays is present in soil?

Potassium fixation is a process that occurs in certain types of clay minerals, specifically illite. In soil, illite possesses a structure that allows for potassium ions to be held tight within its layers. This tight binding leads to difficulties for plants in accessing potassium, which is a vital nutrient for their growth.

The fixed potassium in illite can be difficult for plants to extract compared to other forms of potassium that may be readily available in soil. Illite's ability to "fix" potassium reflects its unique layered structure and the way it interacts with cations. This characteristic sets illite apart from kaolinite, montmorillonite, and sand. While kaolinite and montmorillonite have distinct properties and functions in soil, they do not have the same potassium fixation capability as illite. Sand lacks the clay structure necessary for such fixation entirely, as it does not retain water or nutrients effectively due to its coarse granules.

Consequently, the presence of illite in the soil is directly linked to potassium fixation, making it crucial for understanding nutrient availability and plant health in agricultural practices.