Nature of Soils

What is soil?
Soil may be defined as the naturally deposited unconsolidated material which covers the earth's surface, whose chemical, physical, and biological properties are capable of supporting plant growth. Soil is a product of natural decomposition forces and chemical and physical weathering forces acting upon native rocks, vegetation, and animal matter over an extremely long period of time; in some cases literally thousands of years. The factors involved in the formation of natural soils are: (1) living matter (plants, animals, micro-organisms); (2) climate (cold, heat, snow, rainfall, wind) (3) parent materials (fineness of particle size as well as their chemical and mineralogical composition); (4) relief (slope and landform) and (5) time.

In Suffolk County local differences in the soils are mainly the result of differences in parent material and relief. The climate and vegetation are fairly uniform throughout the county, and most of the soil materials have been exposed to the soil forming processes for about the same length of time.

Soils, naturally, vary widely in their composition depending on their origin along with time and the natural forces involved in their formation process. Given the knowledge of the time required to develop a soil, it is of utmost importance that mankind use this natural resource in cooperation with the laws of nature to optimize soil conservation. This involves both chemical and physical conservation implemented by good management practices. Soil analysis is one aspect of soil management which aids in the conservation of this vital natural resource. Soil testing is an important management tool required for maintaining the proper chemical and microbiological balance within a soil necessary to optimize crop production without depleting the nutrient reserves. Continued survival and dependence of mankind on the soil, demands this balance be maintained through good management practices.

Parent material
The soils of Suffolk County formed in mineral materials, most of which were deposited as a result of glaciation during the Wisconsin age. These materials are (1) glacial outwash consisting of sorted sand and gravel, (2) (glacial) till, and (3) glacial lake-laid silt and clay, which makes up a very small part of the soils of the county. In addition to the formations indicated above, beaches, dunes and narrow isthmuses were more recently formed by the action of waves and wind along the shorelines. In places soils are forming in decomposed or decomposing plant materials that are accumulating in depressions and in tidal marsh areas. The mineral materials are derived mainly from granite and are largely quartz sand.

As the glacier moved over the county, it carried large quantities of rock, much of which was ground into gravel, sand and silt-size particles. Smaller amounts of clay were included. A part of this material was deposited directly by the glacier in a compact, heterogeneous mass called (glacial) till. In addition to the materials carried by the ice, the advancing glacier moved large quantities of material ahead of it. When the advancing ice stopped, the material that was ahead of the glacier was left in place as a ridge called a terminal moraine.

After stopping, the glacial ice melted, and enormous quantities of swiftly flowing water ran from the glacier, carrying and sorting the glacially transported materials. In addition to carrying large quantities of material from the ice, the water reworked the mixed materials in the moraine and left much of it in a stratified condition. Most of the material carried from the glacier was sand and well-rounded gravel, which was redeposited on a broad plain. in front of the terminal moraine. These stratified sand and gravel deposits make up the substratum of most of the soils in the county.

Upon further retreat of the ice, most of the till and parts of the outwash and moraine deposits were covered by water or wind-deposited silt, clay, and fine or very fine sand to varying depths. Haven and Bridgehampton soils are examples of soils formed in silty deposits over stratified sand and gravel. Carver and Plymouth soils are examples of soils formed in deep stratified sandy material containing little or no silt. Montauk soil is an example of a soil formed in a moderately silty material over till.

A very small acreage of soils formed in clayey parent material that was deposited in quiet waters of glacial lakes or ponds. In Suffolk County, Canadice soil is the only soil formed in clayey lake-laid deposits. In a few places, shallow ponds were created when the glacier receded. In these shallow waters, the remains of water-tolerant plants accumulated. Muck soils are forming in these remains of salt-tolerant grasses and reeds around the borders of quieter saltwater bogs. The recently deposited beach and dune sand does not show evidence of soil formation.

All of the various materials deposited in these ways have provided the parent materials in which that soils of the county formed.
-Top of Page-

Relief
The slope and shape of the land surface determine to a large extent the amount of water that enters and passes through the soil and the height to which the water table rises within the soil.

The amount of water that stands on, is contained in, or moves through a soil affects the oxidation, bacterial action, weathering and the amount of removal of the soil minerals within the profile and on the surface. The translocation of components is most noticeable in permeable materials through which water can move readily. The soils in some low lying areas are waterlogged or they have a water table nearer the surface than the soils of adjacent , higher areas. The surface layer of wet soils is darker than that of well-drained soils because the oxidation or organic matter is retarded in wet areas and the organic matter tends to accumulate. Also, the subsoil of wet soils is gray or mottled while that of well-drained soils is a brighter brown or yellowish brown, reflecting the more thorough oxidation of minerals in the well-drained soil.

Soils formed in one kind of parent material, but having different characteristics because of differences in degree of wetness, make up a sequence called a drainage sequence. An example of a drainage sequence is: Carver, Deerfield, Atsion, and Berryland soils. Drainage ranges from excessive in the Carver soils to very poor in the Berryland soils.
-Top of Page-

Climate
Suffolk County has a humid, temperate climate that is strongly influenced by Long Island Sound and the Atlantic Ocean. These bodies of water temper extremes of heat in summer and cold in winter. Climate affects soil formation through its influence on chemical, physical and biological processes. Greater amounts of water passing through the soil effectively alter the chemical composition. Also, chemical changes are accelerated or retarded by changes in temperature. Leaching of soluble salts and translocation of colloidal materials depend directly on the amount of water passing through the soil. Freezing and thawing affect the physical weathering of rocks and soil material. In addition to affecting chemical change, temperature affects the rate of biological activity. Decomposition of organic matter increases as the average annual soil temperature increases. The climate throughout Suffolk County is fairly uniform; therefore, differences in soils in the county are not directly attributed to differences in climate.
-Top of Page-

Time
Geologically, the soils of Suffolk County are relatively young. The last glacier receded from the county about 11,000 years ago; and, to a large extent, all soil forming processes have only had this relatively short period of time to develop the soils as they are known today. Soils have developed in all the materials deposited directly by the glaciers. More recent deposits, such as sand dunes and organic deposits, do not have any recognizable soils formed in them. In some places sand dunes are showing the first vestige of soil formation by the accumulation of organic matter in the upper 2 or 3 inches.
-Top of Page-

Living Matter
The native vegetation in most of Suffolk County was originally hardwoods, mainly oaks, beech, birch, maple, pitch pine, and some white pine. Undergrowth was mainly scrub oak, huckleberry, shadbush, alder, and, in wetter areas, blueberry.

Most of the hardwoods contain some calcium and other bases in their leaves, which are returned to the soils annually as the leaves fall from the trees and rot. Pine needles are more acid and return organic acids to the soil as they fall and rot. In this way, the leachate from the two types of leaves causes differences in soils formed under different types of woodland covered. Soils near Montauk Point have had a grass cover for a sufficient period to materially affect the organic-matter content of the surface horizon.

In addition to the effects of plants, earthworms and larger burrowing animals make the soil more permeable to air and water. Besides altering permeability, animals mix the soil and cause aggregation of soil particles and improve soil structure by addition of animal wastes. Bacteria and fungi form organic acids and other compounds as they break down organic material in the leaves and other compounds within the soils.

Man's activities have brought about significant changes in many of the soils of the country. Tillage has accelerated erosion on sloping soils and has resulted in a mixing of the natural surface layer and the upper sub-soil with organic matter, developing a manmade surface layer 10 to 12 inches thick. In this layer the microbiology of the soil is changed by continued use of lime, fertilizer, and fills have been made for building highways and various structures.
-Top of Page-

Soil Survey of Suffolk County, New York. 1975
United States Dept. of Agriculture, Soil Conservation Service, in cooperation with Cornell Agricultural Experiment Station

Composition of Soils
For discussion purposes, the soils referred to hereafter, will be mineral soils typical of the average farm. Mineral soils are composed of three major constituents: sand, silt and clay. A fourth component, organic matter, although extremely important in the biological, chemical, and physical aspects of the soil, is not generally considered in he textural makeup of mineral soils. The different components of a soil are referred to as fractions, namely, the sand, silt, clay, and organic fractions.

Soils which contain a high clay content are known as clayey or fine textured soils; the silt loams, loams, clay loams, and silts are medium textures soils; and the sands are called course textured soils. Each soil type has been characterized by field and laboratory tests which are based on certain common chemical and physical properties.

Since the sand, silt and clay fractions are predominant in the makeup of mineral soils, the texture of a soil (expressed by the use of Class names, i.e. clay, sandy clay, silt loam, loamy sand, etc.) is based on the relative proportions of these constituents in a given soil. The different Class names are shown in the textural triangle in figure 1.

The colloidal portion (sub-microscopic particle size, large surface area) of soils consists of highly decomposed particles of clay and organic matter, and account for a soil's capacity to hold nutrient elements. These minute clay and organic colloids have a net negative charge, and therefore attract and hold iron, manganese, zinc, and copper. The positive charged metals are called "cations", and the capacity of a particular soil to hold such cations is called the Cation Ion Exchange Capacity (CEC). Hence, the capacity of a soil to hold metal cations varies directly with the CEC of individual soils

The CEC varies considerably from soil to soil depending on the type and percent of colloidal clay and organic fractions present on a given soil. For example, a soil in which sand is the predominant mineral component, would have a low CEC as opposed to a clay soil whose CEC is relatively high. Soils high in colloidal organic matter have an even higher CEC than clay soils.

Since these metal cations of a soil can be displaced through chemical extraction, the CEC of a particular soil can be determined with proper soil test. As a result, the native fertility level of the soil can be assayed and evaluated in light of the extractable nutrient content as it related to the CEC of that soil. For example, soils classified as loams, sandy loams, sandy clays, silt loams, etc. have a much higher CEC than sands, sandy loams or loamy sands, and are less subject to nutrient leaching. Consequently, the extractable nutrient content fraction from these soil classes are generally much higher, which results in higher fertility status and residual benefit. In cases where both fertility status and residual nutrient supplies are high, the need for supplemental fertilizer treatment could be reduced or in unique cases eliminated entirely.

Keep in mind, however, that soils have a limited nutrient reservoir and must be replenished periodically in order to maintain levels with a range required for optimum yields. Remember, also, that soil fertility, as such, is only one aspect of the overall soil management program. Crop rotation, tillage practices, limestone needs, varietal differences, insect and weed control, and water management are other key factors involved in maintaining the productivity of a soil.

The clay content or "colloidal" fraction of soils have a pronounced effect on the nutrient holding capacity, water retention, and ease of tillage. Soils high in clay have a high water retention which can cause tillage delays during wet periods. Clay soils are not very friable as compared with soils which have a low clay content, namely the silt loams, loamy sands, etc. The latter soils types are also much easier worked through various tillage operations.

The clay fraction performs a very useful function in soils, and should be considered a complimentary component of the soil. In addition to enhancing the nutrient and water holding capacity of soils, clay acts as a binding agent in the soil, thereby, bringing about a sort of stability in the soil. Without this "binding" agent, many sandy soils, many sandy soils would have very limited agricultural value. Since the clay fraction accounts for much of the chemical reactivity in soils, it is beneficial in its effects on texture, structure, and consequently, fertility status of a soil. An "ideal" soil is generally defined as a soil composed of a mixture of sand, silt and clay - all of which have their unique effect on the chemical or physical aspects of the soil.
-Top of Page-

Figure 1.

Using a texture triangle such as the one shown, will aid in determining the soil texture class when percentages of sand, silt and clay are plotted. For example, the intersection of the dotted lines show a soil with 13% sand, 32% silt, and 55% clay, has a clay texture because it plots in the clay texture class.