Chapter 5
Soils of Louisiana
By Tonny M. Canales

A soil represents a transformation of surface deposits by means of physical, chemical, and biological process acting through time. Soil commonly occupies the upper six or eight feet of the surface thinning in places to nearly zero depth. The pedogenic process is the process in which soil is formed from changes brought about by a dynamic natural process that causes the soil to form in a particular place working day in and day out. In all, specific soils result from local interactions and among the five soil forming pedogenic factors of parent material, climate, topography, organisms, and time.

Parent material is the geological deposit from which the soil forms. This can be either rock that decomposes in place or sediment deposit such as floodplain, deltaic or terrace alluvium.

Climate is any condition in which influences the many aspects of soil formation such as heat, water or specifically temperature and moisture characteristics. Abundant rainfall aids in translocation of materials downward as water seeps through the soil, and warm and wet conditions favor chemical weathering processes and the production of vegetation.

Topography plays a very critical part because it determines how well drained the soil is and whether it is subject to removal by erosion or by mass movement. On level surface the effects of translocation are much stronger, this could be because of a poorly drained soil.

Organisms refer to a great range of biological phenomena, including the vegetation cover, microorganisms that live on and within the soil, and various kinds of animals that affect soil formation. Most certainly, human activity and development have had a profound effect on the soil as well.

Time refers to the centuries, or tens of centuries, it takes for a soil to evolve on a newly exposed surface. Soil -forming processes are slow, and rates are quite variable depending upon the nature of the parent material and climate in that time frame.

Soil texture is also important, and is determined by the grain size. Soils may be composed mostly of clay, silt, or sand. Clay soils are very tough and difficult to work and tend to remain excessively wet. Sandy soils are easy to work, but tend to be dry and infertile as a result of leaching. An ideal loam has a texture consisting of ten percent clay, fifty percent silt, and forty percent sand.

In Louisiana there are roughly seven general soil regions. Soil series are the soils that have profiles with similar features in which represented in each region. Soil associations are groups of soil series that commonly occur together in a given geomorphic setting. In Louisiana theses soil regions are the Tertiary Upland Solis, Pleistocene Terrace Soil, Flatwoods Soils, Coastal Prairie Soils, Loess Soils, which make up the Soils of the Tertiary and Pleistocene Uplands Plain and the Alluvial Soils, and Gulf Marsh Soils, which make up the Soils of the Holocene Plain.

Maps: Louisiana Gemorphology(adapted from LSU atlas database)

TERTIARY UPLAND SOILS are the large areas of North, Northwest Louisiana areas such as Shreveport, Monroe, Vicksburg, Natchitoches, Tallulah, Ferriday, Lake Providence, Minden, Homer, Haynesville, Arkansas, Bastrop, Columbia, Tullos, Dubach, Ruston, Bernice, Jonesboro, Winnfield, Mansfield, Many just to name a few that have soils developed on Tertiary bedrock. The soils on this Tertiary bedrock has been developed on the oldest known parent material in the hole state and it ranges in age form two to about sixty-five million years, the reddish-yellow coloration is due to the highly soil been highly weathered and oxidized. In this area, it is known to have predominantly short leaf pines and hardwood forested slops and hills.

Topography plays a major roe in that it influences the formation of soils throughout the region. This gives rise to distinct soils in that give association. The Bowie and Ruston soils are located on the level to gently sloping areas and the luck-Troup soils are on the ridge crests and hill slopes. These areas contain low amounts of organic matter with a thin, grayish-brown surface soil and yellow, red or brown sub soils in all this leaves the soil to be somewhat sandy, acidic, and very low in fertility.

PLEISTOCENE TERRACE SOIL correspond to the upland and intermediate terrace complexes and where terrace deposits are found on top of Tertiary- aged rock along the edge of the Red and Ouachita River alluvial plains. These soils are deep and have formed on alluvium ranging in the age around two million and 10,000 years. The frangipane layer has a morphological characteristic of several terrace soils that represents an advanced stage of soil development.

FLATWOODS SOILS are formed under a mixed longleaf pine and hardwood forest environment. The soils in this area are highly acidity because of the pine vegetation.

COASTAL PRAIRIE SOILS are formed on the prairie terrace complex of Southwest Louisiana and have a well-developed soil profile. The clay pan forms when the tiny clay particles in the terrace alluvium are washed downward over time, and then accumulate in a subsurface layer.

LOESS SOILS have developed along the margins of the Mississippi river Valley where loess deposits on the terrace complex are of sufficient thickness for soil profile development. The thin loess sheet of Southwest Louisiana is no calcareous and somewhat less fertile, through sweet potatoes flourish in these loessial soils. The thick loess of the tunica Hills of West Feliciana Parish is calcareous and fertile. Other soil series associated with loess are the Loring, Calhoun, and Memphis soils.

SOILS OF THE HOLOCENE PLAIN, which is, associated to the great variation in alluvial soil series across the Mississippi River, Red and Ouachita floodplains. The dark gray color of the Sharkey and Mhoon soils are due to the high content of organic matter that decomposed under waterlogged conditions. The alluvial soils are the most fertile in Louisiana because of their young age. The majority of the soils in this area are unaltered parent material.

GULF COAST MARSH SOILS are the dark, being that it is black and brown to a light gray in color, and is known to have organic soils from which is drained poorly from the coastal marshes of Louisiana.

Mucks are highly decomposed and typically black in color tone. Peats are unrecompensed, brown in color tone, and form when there is a lack of oxygen under the waterlogged conditions inhibits organic decay. Typically the peas and mucks range in thickness from two feet to over twelve feet lying on top of gray clays. Among the most common soil series are the Allemandes, Bancker, Creoles, Kenner, Scat Lake.

In conclusion Louisiana has great agriculture potential. In some since some of the soils in this state are highly weathered, are acidly, and do contain frangipanes, or even have too much clay or sand to support intensive agriculture. These areas are used mostly for pasture and forest products. In all the most fertile and more productive soils in the states are the young alluvial soils.