Soil-forming factor

Soils develop by the action of the soil forming factors on soil parent materials including material transported by different agents. The result of these soil forming factors is the formation of soil horizons, different colors, and peds. Each of these factors has a pronounced effect on a soil s chemistry. Knowledge of the soil type and profile description can provide the soil chemist, analyst, or researcher with valuable information about the characteristics of soil relevant to the development of extraction, analytical, and instrumental analytical procedures. It also is the place to start when investigating the failure of a procedure. 

The way the five soil-forming factors interact differs from one place to another accordingly, soils may differ greatly from each other. Each section of soil on a landscape has its own unique characteristics. The face of a soil, or the way it looks if one cuts a section of it out of the ground, is called a soil profile. Every soil profile is made up of layers called soil horizons. Soil horizons can be as thin as a few millimeters or thicker than a meter. 

In nature this common set is typically further restricted over wide geographic areas because of the influence or otherwise of soil-forming factors, the most important of which are parent material and degree of weathering. Thus, a typical sample of soil will contain a suite of around six to ten different major minerals. A major mineral may be defined as one that is present at a concentration of a few percent or more, at which it will be readily detectable by routine techniques such as x-ray provider diffraction (XRPD). It is also known as energy-dispersive x-ray analysis (EDXA) or energy-dispersive analysis of x-ray (EDAX) or microscopic examination, either optical or electron. It is also not uncommon for several other minerals to be present in any given soil but usually in amounts that put them below the routine detection limits of many techniques. Nonetheless, these accessory, or trace, minerals can often be concentrated by some means that separates the soil sample into different physical or chemical fractions. Such procedures effectively lower... 

Jenny (1941) proposed that soil development be regarded as the result of five soil-forming factors climate, topography, biosphere, parent material, and time. In a qualitative sense, the weathering rate is related to these factors by... 

The soil-forming factors can modify the distribution of exchangeable cations from this desired state. Table 8.1 shows examples of exchangeable cations found in a wide variety of soils. The Merced soil has high exchangeable Na because it is poorly drained in an arid climate, it has no drainage to the sea, and upwelling water from a... 

Productive agricultural soils are characteristically Ca dominated. One important part of sustainable agriculture is to maintain Ca dominance. Despite the wide range of soil-forming factors in Table 8.1, Ca is the predominant cation in all but the extremely sodic (and barren) Merced soil. 

A striking example for the predominance of vegetation as a soil-forming factor has been reported by Swindale and Jackson [1956]. Local podsolization occurred under Kauri trees in New Zealand as a result of the chelation of iron and aluminum by organic compounds formed during the decomposition of the litter of these trees. 

Mitchell, B. D., 1962. The influence of soil forming factors on clay genesis. Colloq. Int. Centre Natl. Rech. Sci. (Paris, 1961) 105 139. 

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