Higher exchangeable K in soil is associated with:

Correct option is C

· Illite and mica clays have high interlayer K, contributing to higher exchangeable K in soils.
· Weathering of mica releases K⁺ → replenishes soil solution.
Why other options are wrong
· (a) Kaolinite = low CEC, negligible K release.
· (b) Montmorillonite = high CEC but low structural K.
· (d) Allophane (volcanic soils) → low inherent K.