|Soil Orders and CRIFF Groups|
|Between 1951 and 1975, a soil classification
system was developed for the United States. This system was based
on observable, measurable soil properties rather than on the pathways of
soil formation as was the case of the system in use previously.
Soils are classified at six categorical levels: order, suborder, great group subgroup, family, and series. To classify a soil, you must know the soils morphology (features like color, particle size, moisture regime, presence of hardpans and other horizons, depth to bedrock, etc.), and numerous physical and chemical properties such as soil temperature, organic carbon content, sulfide content, mineralogy, and so forth, which require field measurements and or laboratory analysis.
Seven soil orders
occur in Florida. These are summarized in a table. Click on
the link below to see the table:
|Soil Groups for Purposes of Forest Fertilization|
|It is practical to group soils according
to properties that influence the types and amounts of fertilizers needed
for forestry purposes. Soil drainage is a property that can be determined
in the field after minimal experience and is a useful tool for categorizing
forest land for fertilization purposes. This type of categorizing
can also be based on soil phosphorus retention (P-retention) capacity.
1 - Very Poorly to Poorly Drained Soils (Bays and Savannas)
These soils are found in coastal flat lands in mostly level depressions and stream terraces. Most of these soils are flooded from 5 to 30 days, at least once during the growing season. The water table ranges from 6 to 20 inches below the surface during much of the remaining time. These soils were formed under impeded drainage. Therefore, they contain 10% or more organic matter in the surface horizon and most are very acidic and low in nutrient reserves. Vegetation native to these sites include wiregrass (Aristida stricta), pitcher plants (Sarracenia minor), some hardwoods, and a poor to fair growth of pine.
In most cases, pine growth is slowed by excessive moisture and lack of available soil phosphorus. These soils can be grouped according to fertilizer recommendations on the basis of depth to and nature of subsoil horizons, also reflecting their P-retention characteristics:
A - High P-retention: These soils have a dark gray to black fine sandy loam surface, with dark brown to grayish finer-textured material within 20 inches of the surface. Varying degrees of gray mottles reflect the high moisture content of these soils. These wet soils with clay near the surface generally have a high capacity to fix phosphorus in a form only slightly available to trees. The use of ground rock phosphate (GRP) or band placement of soluble phosphates, such as concentrated superphosphate (CSP), is recommended on these sites.
B - Moderate P-retention: These
soils contain fine-textured horizons deeper than the 20 inches of the surface,
but their relatively high organic matter content causes them to have a
moderate capacity to retain phosphorus. Ordinary or slowly-soluble
phosphates can be used on these types of soils.
The flatwoods comprise one of the most extensive groups of forest soils in the Coastal Plain. These acid to loamy sands are low in fertility. Flatwoods soils occupy level to gently sloping flat areas where the water table rises to within 5 to 20 inches of the soil surface for 1 to 4 days, at least once during the growing season. Flatwoods soils support native vegetation such as saw palmetto (Serenoa repens), wiregrass (Aristida stricta), and slash, loblolly, and longleaf pines (Pinus elliottii, Pinus taeda, and Pinus palustris). Flatwoods soils can be grouped into soils with and without organic pans.
A - Low P-retention capacity (Spodosols): Many flatwoods soils contain a weakly cemented organic hardpan that is dark brown to black and occurs from 12 to 40 inches below the surface. This "spodic" horizon may become hard when dry. Flatwood soils with organic hardpans deeper than 16 inches have little capacity to retain P in the soil surface due to their low aluminum and iron content. For this reason, the use of ground rock phosphate (GRP) is recommended for long-term effectiveness.
B - Moderate P-retention capacity: Most
of these soils have fine-textured horizons within 20 to 80 inches of the
surface. Unlike the flatwood-hardpan soils, these soils have moderate
capacity to retain phosphorus. Either ordinary or slowly-soluble
phosphate sources can be effectively used on these soils.
Typically, sands occupy nearly level to rolling regions of the lower Coastal Plain. They have gray to brown surface layers overlaying 30 inches or more grayish- to yellowish-brown sands. These sands have a low capacity to retain water, but they have a reasonably good moisture level because of their topographic position and they are generally considered good forest soils. These soils are often used for pastures, field crops, and vegetables even though they are relatively low in nutrients. Fertilizers must be used to obtain good yields of those crops.
Sand-clay hill sites normally contain red to yellow fine-textured subsoils within 30 inches of the surface. Surface horizons are generally loamy sands to sandy loams. The relatively high clay content of these soils causes them to have good capacity to retain moisture and nutrients and are excellent sites for growing loblolly pine. They are also exceptional agricultural soils.
4 - Excessively Drained Sands (Sandhills)
of these deep sands are in pines in north Florida, Georgia, and the Carolina
sandhills. Water deficits limit responses to fertilizers even on
the most nutrient-deficient sites. In general, fertilizers are not
recommended for pine plantations in the sandhills due to moisture limitations.
However, 150 lb DAP/acre (banded)
may be effectively used on young sand pine, while urea is sometimes recommended
for older stands of sand pine on excessively drained sands.