Leaching is the process by which soluble substances are washed out from solid materials, often occurring in soil or rock. This can happen when water, usually from rainfall or irrigation, seeps through the ground, carrying away nutrients and minerals. Leaching can affect soil fertility, as essential elements like nitrogen and potassium may be lost, impacting plant growth. In environmental contexts, leaching can also refer to the movement of contaminants from waste materials into groundwater. For example, when landfills are not properly managed, harmful chemicals can leach into the soil and water supply, posing risks to ecosystems and human health.