The zone of leaching is primarily found in the E horizon, also known as the eluvial horizon.

Here's why:

* E Horizon: This horizon is characterized by the loss of minerals and organic matter due to the downward movement of water. It's where leaching, the process of water carrying dissolved minerals and organic matter down through the soil profile, is most prominent.

* Other Horizons: While leaching can occur in other horizons like the A horizon (topsoil), the E horizon is specifically defined by its intense leaching activity.

Important Note: The E horizon is not always present in all soil profiles. Its presence depends on the specific soil-forming factors in a particular location.