Abstract

The soil is a mixture of mineral and organic particles of various sizes, water and the air. The proportion of these soil components determine the physical makeup and other properties of the soil. The mineral matter constitutes of three primary soil particles based on their equivalent spherical diameter (esd), sand (2–0.05 mm), silt (0.05–0.002 mm) and the clay (<0.002 mm). The percent distribution of these three primary particles determines the soil texture class. There are 12 soil textural classes in the USDA system. In Kuwait major soil texture classes are sand and loamy-sand. At the global and national levels, there is wide diversity of soils with different physical, chemical, mineralogical and biological properties. This diversity makes soils one of the most complex natural systems that what we attempt to classify for informed decisions for land use planning and national development. The lower boundary of soil that we classify is arbitrary set at 200 cm. Soil, as defined in this text, does not need to have discernible genetic horizons, although the presence or absence of genetic horizons and their nature are of extreme importance in soil classification. The Kuwait Soil Taxonomy is presented in a way to key out soils starting from the beginning and eliminating one by one not matching the criteria to the soil in

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S. A. Shahid and S. A. S. Omar, Kuwait Soil Taxonomy, https://doi.org/10.1007/978-3-030-95297-6_2

the field until correct name of surface and subsurface horizons are identified and a correct soil taxa name is designated to the location under investigation.

Keywords

Buried soil Soil formation Lower boundary Classification Taxonomy

2.1Introduction

Soils are one of the most important components for agrifood systems, but also one of the most fragile: the formation of a centimeter of land requires hundreds of years of work, and can be destroyed in seconds. Therefore, we must encourage conservation practices and the adoption of technologies to restore degraded land and protect those that are still functional. This requires proper understanding of national soils using internationally recognized soil classification system which fits the countries climatic conditions and covers the soil formation processes and soil taxonomic classes.

The word “soil” has diversified meanings based on its use for a specific purpose. For a potter who makes and sell soil based pottery, it is a source material for pots production, for a civil engineer, soil is construction material (houses, road beds etc.) and foundations for buildings, soil also provides materials for ceramics, and medium for industrial and waste disposal, protects groundwater by filtering toxic chemicals etc.. From the point of view of an agriculturist, it is “natural medium for the growth of land plants, whether or not it has discernible soil horizons or layers”. The soil supports plants that supply food, fibers, drugs, and other wants of humans and because it filters water and recycles wastes. In addition, the soils are considered dynamic ecosystems capable of supporting plant and wildlife. Soil is considered “skin” of the planet earth. Soil formation (Jenny 1941) is a function of climate (cl), organism (o), relief (r), parent material (p) and time

(t) and expressed as S = f (cl, o, r, p, t).

National soil classification is essential to understand the history of soil formation, explaining the distribution and heterogeneity on the landscape, understanding soil properties, soil formation processes and modeling, land use evaluation and relationship with the environment and for the provision of ecosystem services.

2.2The Soil That We Classify

Soil in this text is a natural body comprised of solids (minerals and organic matter), liquid, and gases that occur on the land surface, occupies space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment (Soil Survey Staff 1999). This definition is expanded from the previous version of Soil Taxonomy (Soil Survey Staff 1975). The upper limit of soil is the boundary between soil and either air, shallow water, live plants, or plant materials that have not begun to decompose. Areas are not considered to have soil if the surface is permanently covered by water too deep (typically more than about 2.5 m) for the growth of rooted plants. The horizontal boundaries of soil are areas where the soil grades to deep water, barren areas, rock, or ice. Soil is not static, but dynamic. The pH, soluble salts, amount of organic matter and carbon–nitrogen ratio, numbers of microorganisms, soil fauna, temperature, and moisture status all change with the seasons as well as with more extended periods of time. Soil must be viewed from both the short-term and long-term perspective (Soil Survey Staff 2014).

2.3Lower Boundary of Soil

Soil consists of the horizons near the earth’s surface that, in contrast to the underlying parent material, have been altered by the interactions of climate, relief, and living organisms over time (Jenny 1941). For the practicality of soil survey, the lower boundary of soil is arbitrarily set at 200 cm. In areas where soil has thin,

pedogenically cemented horizons that are impermeable to roots, the soil extends as deep as the deepest cemented horizon, but not below 200 cm. For certain management goals, layers deeper than the lower boundary of the soil that is classified (200 cm) must also be described if they affect the content and movement of water and air or other interpretative concerns.

2.4Nonsoil Materials

Plants can be grown under glass in pots filled with earthy materials, such as peat or sand, or even in water. Under proper conditions all these media are productive for plants, but they are nonsoil here in the sense that they cannot be classified in the same system that is used for the soils of a survey area, Governorate, or even nation. Plants even grow on trees or in cracks of exposed bedrock (i.e., rock outcrop), but trees and rock outcrop are regarded as nonsoil.

2.5Buried Soils

A buried soil is a sequence of genetic horizons in a pedon that is covered with a surface mantle of new soil material, that is 50 cm or more thick. In Kuwait, the mobile sand usually covers the genetic horizons, thus can be considered a buried soil.

The hierarchy of soil classification (KISR 1999a, b) has been used to prepare Kuwait Soil Taxonomy. It is hoped that this key will be widely used by the potential soil information seekers to find locations for specific purposes.

References

Jenny H (1941) Factors of soil formation. McGraw-Hill, New York, London

KISR (1999a) Soil survey for the state of Kuwait: reconnaissance survey, vol II & III. Kuwait Institute for Scientific Research, Kuwait

KISR (1999b) Soil survey for the state of Kuwait: semi-detailed survey, vol IV & V. Kuwait Institute for Scientific Research, Kuwait

Soil Survey Staff (1975) Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. Soil Conservation Service. U.S. Department of Agriculture Handbook, vol 436

Soil Survey Staff (1999) Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys, 2nd edn. Natural Resources Conservation Service. U.S. Department of Agriculture Handbook, vol 436

Soil Survey Staff (2014) Keys to soil taxonomy, 12th edn. US Department of Agriculture, Natural Resources Conservation Service, US Government Printing Office, Washington, DC

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