Why is infiltration capacity often higher in coarse-textured soils than in fine-textured soils?

Why is infiltration capacity often higher in coarse-textured soils than in fine-textured soils?

• A. Coarse soils have larger pore spaces and less resistance to flow; infiltration encounters fewer capillary and tortuosity barriers.
• B. Fine soils have larger pore spaces and allow easier infiltration.
• C. Infiltration capacity is higher in fine soils.
• D. Infiltration capacity does not depend on texture.

Answer: (A)

Infiltration capacity is essentially how fast water can enter the soil, which depends on the size and connectivity of the pores through which water moves. Coarse-textured soils like sands have larger pore spaces and better-connected pathways, so water faces less resistance as it moves downward. Capillary forces are weaker in these large pores, and there are fewer narrow constrictions or tortuous routes to slow the flow. That means the soil can accept water at a higher rate, approaching its saturated hydraulic conductivity, until the surface or subsurface becomes saturated or the soil structure changes. In fine-textured soils, the pores are smaller and more numerous, which increases capillary suction and creates many narrow pore throats. Water must navigate a more tortuous path, so movement is hindered and infiltration proceeds more slowly, reducing infiltration capacity. Some of the other ideas would imply that fine soils infiltrate faster or that texture doesn’t matter, but the strong influence of pore size distribution and flow resistance makes coarse textures the soils with higher infiltration capacity.

Infiltration capacity is essentially how fast water can enter the soil, which depends on the size and connectivity of the pores through which water moves. Coarse-textured soils like sands have larger pore spaces and better-connected pathways, so water faces less resistance as it moves downward. Capillary forces are weaker in these large pores, and there are fewer narrow constrictions or tortuous routes to slow the flow. That means the soil can accept water at a higher rate, approaching its saturated hydraulic conductivity, until the surface or subsurface becomes saturated or the soil structure changes.

In fine-textured soils, the pores are smaller and more numerous, which increases capillary suction and creates many narrow pore throats. Water must navigate a more tortuous path, so movement is hindered and infiltration proceeds more slowly, reducing infiltration capacity. Some of the other ideas would imply that fine soils infiltrate faster or that texture doesn’t matter, but the strong influence of pore size distribution and flow resistance makes coarse textures the soils with higher infiltration capacity.