The process by which clay and humus particles attract and hold nutrient cations in the soil is known as

Cation exchange is the process whereby negatively charged clay and humus colloids attract and hold positively charged nutrient ions (cations) such as Ca²⁺, Mg²⁺, and K⁺. These cations can be released and exchanged with other cations in the soil solution, making nutrients available to plant roots. This is a fundamental mechanism of soil fertility.