LAA.Sulfaquents

Key to Great Groups 

LAA. Aquents that have sulfidic materials within 50 cm of the mineral soil surface. Sulfaquents, p. 403 

LAA. These are the Aquents that have an appreciable amount of sulfides close to the mineral soil surface and have few or no carbonates. The sulfides are close enough to the surface for the soils to become extremely acid and virtually sterile if drained. These soils are largely restricted to coastal marshes where the water is brackish. Tidal marshes at the mouth of rivers normally have areas of these soils unless the river sediments are rich in carbonates. Coastal marshes that are not near rivers also may have areas of these soils if storms periodically flood them with salt water. Sulfaquents are permanently saturated at or near the surface, and many are nearly neutral in reaction. The n value typically is high, commonly more than 1 in most horizons. A histic epipedon composed of organic soil materials is common. These soils can have any mineral particle-size class, but those with less than 8 percent clay are not considered typical. If the soils are drained, the sulfides oxidize and the soils change rapidly to Sulfaquepts. Sulfaquents commonly are not used as cropland, but some are used for the production of rice. The areas used for rice are kept flooded at all times, except for a very brief period while the crop is harvested. Sulfaquents are extensive along coasts and bays from the Equator to high latitudes. They are moderately extensive on the east coast of the United States, where they border the Atlantic Ocean in areas not protected by barrier islands. 

Definition 

Sulfaquents are the Aquents that have sulfidic materials within 50 cm of the mineral soil surface. 

Key to Subgroups 

LAAA. Sulfaquents that have, in some horizons at a depth between 20 and 50 cm below the mineral soil surface, either or both:

1. An n value of 0.7 or less; or

2. Less than 8 percent clay in the fine-earth fraction. Haplic Sulfaquents 

LAAB. Other Sulfaquents that have a histic epipedon. Histic Sulfaquents 

LAAC. Other Sulfaquents that have a buried layer of organic soil materials, 20 cm or more thick, that has its upper boundary within 100 cm of the mineral soil surface. Thapto-Histic Sulfaquents 

LAAD. Other Sulfaquents. Typic Sulfaquents 

Definition of Typic Sulfaquents 

Typic Sulfaquents are the Sulfaquents that:

1. Do not have, in one or more horizons at a depth between 20 and 50 cm below the mineral soil surface, either or both:

                a. Less than 8 percent clay in the fine-earth fraction; or

                b. An n value of 0.7 or less;

2. Do not have a histic epipedon;

3. Do not have a buried layer of organic soil materials, 20 cm or more thick, that has its upper boundary within 100 cm of the mineral soil surface.

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