25. Classification Of Soils

The Bureau of Soils of the United States Department of Agriculture has established a system of soil classification which should be familiar to every student of vegetable gardening.

26. Soil Type

The unit of classification is known as a type. Soil Survey Field Book, 1906, p. 16: "In the determination of a type of soil there are many factors to be considered. Among the most important are the texture, which deals with the size of the particles; the structure, which deals with the arrangement; the organic matter-content, origin, color, depth, drainage, topography, native vegetation and natural productiveness. This classification is based primarily upon the physical properties, but all factors that influence the relation of soils to crops, so far as their influence can be determined, are taken into consideration."

27. Soil Class

Ibid., p. 16: "Soil types which constitute the units of soil classification, may be grouped in different ways. As soils are made up of particles of different sizes, they may be grouped according to the relative proportions of the particles of different sizes which they contain. This grouping is known as the soil class and is based on texture. By means of mechanical analyses the particles less than two millimeters in diameter are separated into seven grades, and the various percentage relationships of the different grades determine the class of soil; that is, they determine whether it is sand, sandy loam, loam, clay or some intermediate class. In addition to the fine earth, of which a mechanical analysis is made, many soils contain larger particles, which if small are called 'gravel,' and if of larger size are called 'stones,' so that in the soil classification it is possible to have a gravelly sand, loam, or clay, and likewise stony members of the various classes." The table on the opposite page (ibid., p. 17) will give the reader a better knowledge of soil classification:

Scheme Of Soil Classification



Fine gravel

2-1 mm.


Coarse sand 1-0.5 mm.


Medium sand 0.5-0.25 mm.

4 Fine sand

0.25-0.1 mm.


Very fine sand

0.1-0.05 mm.



0.05-0.005 mm.


Clay 0.005-0 nun.

Coarse sand

More than 25% of 1 + 2



More than 50% of 1 + 2 + 3

Less than 20% of 6 + 7

Medium sand

Less than 25% of 1 + 2



More than 20% of 1 + 2 + 3

Less than 20% of 6 + 7

Fine sand



Less than 20% of 1 + 2 + 3

Less than 20% of 6 + 7

Sandy loam



More than 20% of 1 + 2 + 3

More than 20% and less than 50% of 6 + 7

Fine sandy loam



Less than 20% of 1 + 2 + 3

More than 20% and less than 50% of 6 + 7



Less than 55% of 6

More than 50% of 6 + 7

Silt loam

More than 55% of 6

Less than 25% of 7

Clay loam



More than 60% of


Sandy clay

Less than 25% of 6

More than 20% of 7

Less than 60% of 6 + 7

Silt clay

More than 55% of 6

25-35% of 7


More than 35% of 7

More than 60% of


28. Soil Series

"It has been found that in many parts of the United States the soil classes of a given set are so evidently related through source of material, method of formation, topographic position, and coloration that the different types constitute merely a gradation in the texture of an otherwise uniform material. Soils of different classes that are thus related constitute a series. A complete soil series consists of material similar in many other characteristics, but grading in texture from stones and gravel on the one hand, through the sands and loams, to a heavy clay on the other." Ibid., p. 19.

29. Atlantic And Gulf Coastal Plains

This soil province includes all of Delaware and Florida and parts of Long Island, New Jersey, Maryland, Virginia, North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana and Texas, and the following soil series are important to vegetable growers: Bastrop, Crockett, Laredo, Lufkin, Norfolk, Orangeburg, Portsmouth, Sassafras, Susquehanna and Webb. Of the miscellaneous trucking soils of this province the following may be mentioned: Collington sandy loam, Hempstead loam and muck and peat.

30. Bastrop Series

In Texas, 58,432 acres. (United States Bureau of Soils, Bul. 55, p. 97.) Melons and potatoes do well on the silt loams. The fine sandy loams are exceptionally well adapted to melons, potatoes, peanuts and vegetables when irrigated.

31. Crockett Series

In Texas, 29,504 acres. The gravelly loam is well adapted to early vegetables.

32. Laredo Series

In Texas, 55,040 acres. Ibid., p. 101: "Laredo silty clay loam, mapped in the Brownsville area, Texas, is a very productive soil and well adapted to growing early vegetables. . . . Lettuce, melons, cauliflower, beets, peas, cabbage, onions, eggplant, cucumbers, tomatoes, carrots and both sweet and Irish potatoes are all profitably grown under irrigation. Cabbage is the principal crop and the average yield is about 18,000 pounds an acre. . . . The clay loam is well adapted to the growing of onions, giving an average yield of about 20,000 pounds an acre." Vegetables do well on other types of the Laredo series when irrigation is practiced.

33. Lufkin Series

In Texas, Mississippi, Alabama and Louisiana, 1,375,808 acres. Loam and sandy loam are adapted to potatoes, cucumbers and other vegetables.

34. Norfolk Series

In the Coastal Plain, 9,612,882 acres make the Norfolk series the most important trucking soil. It has a wide general distribution from Long Island to Texas. The fine sand is considered the leading soil for general trucking; 1,319,164 acres of this type have been surveyed. The Norfolk sand is an important soil because of its extreme earliness. It is especially valuable for the growing of radishes, spinach and other light crops for the early market. In North Carolina, asparagus is profitable on this soil and it produces excellent crops of early potatoes and lettuce in Virginia. The Norfolk sandy loam is largely planted in Irish and sweet potatoes and other heavy truck crops.

35. Orangeburg Series

From North Carolina to Texas, 3,486,464 acres of the Orangeburg series are distributed. The sandy types are well adapted to cabbage, kale, lettuce and the root crops. The heavier types are used for celery, onions and cabbage.

36. Sassafras Series

In Maryland, 407,344 acres. Tomatoes are extensively grown in loams and sandy loams, which are also well adapted to medium early truck. The sandy types are light, well-drained soils and well suited to peas, asparagus, Irish potatoes and other vegetables.

37. Susquehanna Series

In Texas, Louisiana, Alabama, Mississippi, North Carolina and Maryland, 1,495,-990 acres. The fine sandy loam is well suited to truck crops.

38. Webb Series

In Texas, 184,512 acres. When the content of organic matter is large, the fine sandy loam is well adapted to growing Bermuda onions. Other vegetables have been grown to some extent.

39. Collington Sandy Loam

Over 110,000 acres of this soil have been mapped in New Jersey and Maryland. It is one of the most productive soils of the trucking types.