Why do sandy and gravelly soils dry out quickly?

In the context of gardening, sandy and gravelly soils are characterized by their large particle size, which classifies them as "light" soils that are easy to cultivate. However, these soils dry out quickly because they possess a very low water-holding capacity.1

The physical reason for this lies in the relationship between grain size and porosity. Sandy soils consist of larger particles compared to clay or silt, resulting in larger pore spaces between the grains. While smaller pores in finer-textured soils help retain moisture and nutrients by bringing them into close proximity with chemical binding sites, the larger pores in sandy and gravelly soils allow water to drain through them rapidly. Because these soils struggle to retain moisture, they are often referred to as "hungry" soils, requiring significant additions of humus, manures, and fertilizers to remain productive for plants.21