Top dressing is putting a compost, sand, or soil mix on the surface of a lawn. Top dressing improves and fertilizes soil, protects plants, smooths lawns, and reduces thatch build up. The soil is applied in a thin layer, usually around a quarter of an inch. It can be spread using shovels and rakes or by a motorized top dresser. Although top dressing is generally seen as a positive way to improve your garden, it is quite time intensive.