Certified Crop Advisor Practice Exam

What term describes rapid water movement downward in large pores after a rain event?

1. Capillary flow

2. Preferential flow

3. Surface runoff

4. Gravitational flow

The correct answer is: Preferential flow

The term that describes rapid water movement downward in large pores after a rain event is preferential flow. This process occurs when water moves quickly through channels in the soil that are larger than the finer pores, which can happen due to factors such as soil structure, texture, and existing voids in the soil. As rainwater infiltrates the soil, it follows these larger pathways, allowing for rapid drainage and minimizing the time water stays in the upper soil layers. Preferential flow is significant in understanding how water and nutrients move through the soil profile, which can impact agricultural practices, drainage, and even contaminant transport. Gravitational flow, while related, specifically refers to the role of gravity in moving water downward, often through all pore sizes, but it doesn't emphasize the rapid movement in large pores that characterizes preferential flow. Capillary flow involves the movement of water in smaller pores due to capillary forces and is generally slower compared to the rapid movement in preferential flow. Surface runoff, on the other hand, refers to water that flows across the soil surface rather than infiltrating into the soil, making it a distinct process from what is described in the question.