i. Spodosols usually have four very distinct layers: a surface layer of partly decayed organic matter, a light upper layer of coarse leached material, a dark lower layer where organic material and aluminum from the leached layer accumulate, and finally, the unaltered parent material.
ii. The subsurface layer of organic matter and aluminum (the spodic horizon) is the essential diagnostic feature.
iii. Ordinarily, spodic horizons form only on sand in rainy areas, often but not always under needle leaf trees.
iv. In the United States the proper combination of conditions occurs mainly in northern forests, high mountains, and salt marshes along some seacoasts.
v. Soils with spodic horizons are usually very acid, low in nutrients, and poor for farming, except for acid-tolerant crops, such as potatoes, blueberries, or cranberries. Irrigation and fertilization have made some spodosols very productive, but the cost is very high.