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Parent Material Soil Drainge Class Gravel Content in Deep Soil Effective Soil Depth Soil Texture
During a field study, morphological and physical characteristics of soil such as parent material, soil texture, topography, soil drainage classes, gravel content, slope, effective soil depth, and the rate of erosion are often used to determine the series, order, and age of a soil. Topography, soil drainage classes, soil texture, effective soil depth, and gravel content not only play important roles in determining soil series, but along with vegetation and climate are significant and fundamental factors for both understanding the formation of soils and analyzing the characteristics of farmland.

Determination of parental material is the first step in conducting a soil survey. A rock may be an assemblage of minerals bound together or it may be a mass of a single mineral. Thousands of rocks have been identified but they can be classified into three categories of the rock-forming processes: igneous rocks,

sedimentary rocks, and metamorphic rocks. Igneous rocks are sub-classified into acidic igneous rocks, neutral igneous rocks, and alkalic igneous rocks. Sedimentary rocks are usually formed from sedimentary deposits that are mechanically transported by water. Sedimentary rocks can be classified by their grain size into shale, sandstone, and conglomerate, and by their mineral content into limestone, zeolite, and diatomite, and by the degree of petrification into hard rocks and semi-petrified rocks. Soil scientists classify parent rocks into the following categories: acidic rocks, neutral rocks, alkalic rocks, sedimentary rocks, metamorphic rocks, Tertiary deposits, Quaternary deposits, and volcanic ash.

(Source: Korean Rural Development Administration, National Institute of Agricultural Science and Technology, 2007)