Which soil type is characterized as coarse and having fewer adsorptive sites for herbicides?

The correct answer is sand, which is characterized by its coarse texture and larger particle size compared to other soil types. Sand has a lower surface area and fewer adsorptive sites, meaning it has less capacity to hold on to herbicides. This lower adsorption can lead to faster leaching of herbicides through the soil, making sand less effective for retaining these chemicals compared to finer soils like clay and silt.

Clay, in contrast, is composed of very fine particles that have a high surface area and can hold onto moisture and nutrients, including herbicides, more effectively. Silt has a medium particle size between sand and clay, offering moderate retention capabilities. Organic matter plays a critical role in improving soil structure, nutrient retention, and holding capacity for herbicides, further differentiating it from sand. Thus, the unique characteristics of sand as a coarse soil type with minimal adsorptive properties make it the correct choice for this question.