About 75 percent of Moldova is covered by a soil type called black earth or chernozem. In the northern hills, more clay textured soils are found; in the south, red-earth soil is predominant. The soil becomes less fertile toward the south but can still support grape and sunflower production. The hills have woodland soils, while a small portion in southern Moldova is in the steppe zone, although most steppe areas today are cultivated. The lower reaches of the Prut and Dniester rivers and the southern river valleys are saline marshes.