What type of irrigation would likely be least effective in sandy soils?

Surface irrigation is likely to be the least effective type of irrigation in sandy soils due to the inherent characteristics of sandy soil that affect water retention and distribution. Sandy soils are known for their large particle size and high permeability, which allows water to drain quickly. When surface irrigation is employed, water is typically applied to the surface of the soil, which can lead to uneven distribution and significant runoff in sandy conditions.

In sandy soils, the rapid infiltration and drainage rates can result in water not being adequately absorbed by plant roots, leading to poor moisture retention. In contrast, methods like drip and subsurface irrigation deliver water directly to the root zone, reducing evaporation and ensuring more efficient water use. Sprinkler irrigation, while still subject to some degree of evaporation, can cover areas more evenly and might be more effective than surface irrigation in sandy soils when implemented correctly. Thus, surface irrigation is less suited for the challenges posed by sandy soils.