Concept:Leaching is the removal of soluble soil nutrients by percolating water.Explanation:When rainwater or irrigation water moves downward through the soil, it dissolves soluble nutrients such as nitrates, potassium, and calcium.These dissolved nutrients are carried away from the topsoil to lower layers or beyond the reach of plant roots.Thus, leaching is best described as the washing down of soil nutrients from the soil profile.Answer:B. Washing down of soil nutrients