The maritime climate and deciduous forests of much of France promoted the development of what are generally called podzolic soils. The podzolic process involves the leaching, or carrying away, of material near the surface by moderately acidic water that has seeped through plant material on the forest floor. Podzolic soils are gray-brown and tend to be heavy, with a high clay content. They can be moderately productive for agricultural use when properly fertilized and carefully managed.
In the Paris Basin, soils have been derived from limestone formations, which make them exceptionally rich in minerals useful for agriculture. In postglacial times this region was covered by a thin coating of fine, windblown material called limon (silt), much of which has high nutritive value.
In contrast, where granites and related rocks are the base for soil formation, as in Brittany, the soils tend to be acidic and comparatively unproductive. Along many coastal areas, and especially in parts of the Aquitaine Basin, light sandy soils are impractical for agriculture. In mountainous regions, soil formation is difficult because of steep slopes, and soil erodes downward as it forms. Because of the lack of abundant grassland, France has only small amounts of the rich organic soils so vital to such regions as the American Midwest and the rich grain fields of Ukraine.