Which of the following textural classes has the largest potential available water?

Silt loam has the largest potential available water among the textural classes listed. This is due to its balanced particle size distribution that includes both fine and coarse particles. The texture of silt loam allows for optimal water retention while still providing good drainage.

The smaller particles in silt loam, such as silt, have a greater surface area relative to their volume compared to sand and loamy sand. This allows them to hold more water in the soil pores as they can retain moisture more effectively than coarser textured soils. At the same time, the presence of some sand granules in the mix prevents water from becoming overly compacted, facilitating drainage and root penetration.

In contrast, clay retains a significant amount of water due to its small particle size and high surface area, but it can also become waterlogged, limiting the availability of water for plant uptake. Sandy loam and loamy sand consist primarily of larger sand particles, which have lower water holding capacity because they drain too quickly, leaving less water available to plants.

Therefore, silt loam, with its ideal combination of water holding capabilities and drainage, stands out as having the highest potential for available water in comparison to the other textural classes.