Soil formation factors

Jenny (1941) attempted to quantitatively relate the factors of soil formation to soil properties such as N, C, or clay content, depth of leaching... 

Jenny, H. (1941). "Factors of Soil Formation A System of Quantitative Pedology." McGraw-Hill, New York. 

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. 

Figure 6.2. (A) Variations in %N (which is proportional to C density) with precipitation along the 11 °C isotherm in the Great Plains of the United States. The humidity factor (NSQ, Niederschlag-Sattigungsdefizit from the German, or Meyer s quotient) is the total annual precipitation (mm) divided by the absolute saturation deficit of air (mm mercury). All soils were developed on loess deposits from the last glacial maximum. (B) Change in %N with precipitation along the 19 °C isotherm. Note that relative C density (estimated by assuming that the C/N ratio of SOM is fairly constant) is lower at higher mean annual temperature. Reprinted with permission from Jenny, H. (1941). Factors of Soil Formation, Dover Publications, New York.

Factors of soil formation were proposed in the 1860s in the United States by E. W. Hilgard (Jenny 1961a) and in the 1880s in Russia by V. V. Dokuchaev (Krupenikov 1993) and have been developed in a semiquantitative fashion by Jenny (1941, 1961b, 1980), who formulated the now well-accepted Clorpt equation. Soil formation and the properties of the soil are the result of the following five key factors ... 

Wilding, L. P. (1994). Factors of soil formation Contributions to pedology, in Factors of Soil Formation A Fiftieth Anniversary Retrospective (R. Amundson, J. Harden, and M. Singer, Eds.). Madison, WI Soil Science Society of America, 15-30. 

In many cases cultivated soils have compacted areas which can severely impair tree growth. Compaction in soil may be due to factors associated with soil formation or geology, or it may have been caused by mechanical pressure from machinery or by deposits by transport and ground-levelling vehicles. If the soil is compacted it is absolutely essential to loosen the subsoil (e.g. by trenching or deep cultivation) before a new orchard is set up. Dwarfing rootstocks for apples and pears (M9, M27, quince C), elder and small fruit trees are particularly sensitive to soil compaction. 

Ponomareva, V. V., and V. V. Dokuchayev. 1984. Water-mineral nutrition of plants as a major factor in phytogenesis and soil formation. Pochvovedeniye. 1984(4) 29-38. 

The purpose of this chapter is to present an abridged overview of the factors and processes that control soil formation, and to provide, where possible, some general statements of soil formation processes that apply broadly and commonly. 

Jenny (1941) applied principles from the physical sciences to the study of soil formation. Briefly, Jenny recognized that soil systems (or if the aboveground flora and fauna are considered, ecosystems) exchange mass and energy with their surroundings and that their properties can be defined by a limited set of independent variables. From comparisons with other sciences, Jenny s state factor model of soil formation states that... 

These so-called state factors of soil formation have the following important characteristics (i) they are independent of the system being studied and (ii) in many parts of the Earth, the state factors vary independently of each other (though, of course, not always). As a result, through judicious site (system) selection, the influence of a single factor can be observed and quantified in nature. 

Table 1 provides a brief definition of the state factors of soil formation. A field study designed to observe the influence of one state factor on soil properties or processes is referred to as a sequence, e.g., a series of sites which have similar state factor values except climate is referred to as a climo-sequence. Similar sequences can, and have been, established to examine the effect of other state factors on soils. An excellent review of soil state factor studies is presented by Birkeland (1999). An informative set of papers discussing the impact of Jenny s state factor model on advances in pedology, geology, ecology, and related sciences is presented in Amundson et al. (1994a,b). 

Jenny H. (1941) Factors of Soil Formation. McGraw-Hill, NY. 

Surficial processes that affect the redox composition of Earth materials include weathering, drainage, groundwater movement, mechanical mixing and dispersion of rock material, soil formation, the accumulation of organic material and biological processes. There is an almost unlimited number of ways in which these factors can combine to affect the composition of Earth materials and therefore to affect local redox conditions. However, the processes that are most likely to affect redox locally can be simplified. 

One result of human appropriation of the earth s terrestrial resources is soil degradation, which is widespread worldwide, rates of soil loss exceed rates of soil formation by at least a factor of 10. 

Blumel, W.D. (1982) Calcrete in Namibia and SE-Spain. Relations to substratum, soil formation and geomorphic factors. Catena Supplement 1, 67-82. 

Retallack, G.J. (1994) The environmental approach to the interpretation of paleosols. In Amundson, R., Harden, J. Singer, M. (Eds) Factors of Soil Formation a Fiftieth Anniversary Retrospective. Special Publication 33. Madison, WI Soil Science Society of America, pp. 31-64. 

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