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Learn to determine soil textures by feel, identify colors using Munsell system, and understand horizon nomenclature for soil profiles. Practice texture classification with sandy, silty, and clay soils. Explore soil color components like hue, value, and chroma. Understand soil horizon suffixes and transitions to describe profiles accurately.
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Activities for Today • Texture: Determine texutral classes by feel, and identify textures of unknown samples; • Soil Color: Understand terminology of the Munsell color system (hue, value, chroma) and use it to determine soil color; • Learn the nomenclature for master horizon suffixes, and transition horizons, and use them in labeling horizons on a monolith or soil profile description.
Soil Texture • Textural classes of soils are named on their predominant feel and correspond to percentages of sand, silt, and clay.
Soil Texture • Sandy textures- feel gritty • Silty textures- feel smooth, soft, and floury • Clay textures- stiff, waxy, and plastic
How to Texture • Golf-ball-sized amount of soil in your hand • Soil needs to be moist but not wet(add water slowly) • Knead the soil in your hand, between your thumb and fingers. • Ribbon (?)/ Gritty, waxy, smooth
Soil Color • Dark brown to black- ( A horizon) top soils, humus- decomposed organic material. A few percent of humus gives a brownish color and up to 5% the soil becomes black.
Soil Color • Reds and Yellows- (B horizons) iron oxide formed during weathering, • Fe+3 is well oxidized (well-drained)
Soil Color • Grey colors are caused by reduced Iron (Fe+2 ) • Water has excluded oxygen from diffusion into soil • Other pigments are leached out from horizons (humus, iron oxides)
Soil Color Determination Hue- is the dominant spectral color of the entire page of chips. 10YR- all chips on the page are composed of 10 parts of yellow(Y) to 1 part red(R). Value – lightness or darkness of the color. 8- light color and 2 – dark color (high humus content) Chroma- brightness or dullness of a color chip. 1- dull (grayish/waterlogged) and 8 bright (oxidation)
10YR 5/3 Munsel Color Chart Hue Value Chroma
Soil Color • Matrix color- main or background color • Mottles – other colors within the matrix • Redoximorphic features-reduction of Fe and oxidation of Fe.
Horizon Designations • O Horizon: organic debris a – Highly decomposed litter e – intermediate , partially decomposed litter i - slightly decomposed, identifiable litter A Horizon: contains humus p – plowed, shown by sharp boundary with horizon below ( abrupt transition) b – buried, A-type horizon found buried in profile E horizon: light-colored, leached; NO suffixes
Horizon Designations • B Horizon: material moved INTO h- illuvial humus present t- clay inc. compared to A; clay films w- NO clay increase; blocky structure *g- gleyed(chroma ≤ 2) C Horizon: weathered parent material r- hard to dig; almost R *g – gleyed (chroma ≤ 2) “types” of B horizons: only 1 in each profile
Horizon Designations • Suffixes that are number are used to indicate different parts of the same horizon. Bt-Bt1, Bt2 • Transition horizon- occurs between two master horizons that have the properties of both. “AE” transition layer is between A and E horizons, more like an A than an E.
O: leaf litter at top either “a”, “e”, or “i” A: topsoil (humus) add “p” if abrupt E: same texture as A; often light color Transition horizons: either EB or BE B horizon either “t”, “w”, or “h”; add “”g” Transition (maybe) C horizon: add “g” or “r” if necessary R: cant dig it….
Soil Profile _ 0-1” hardwood leaves and twigs _ _1”-6” 10YR 3/4 sandy loam granular _ _6”-13” 10YR 6/3 sandy loam granular _ 13”-25” 2.5YR 4/6 clay blocky _ 25”-35” 5YR 5/6 clay loam blocky _ _35”-47” saprolite massive _ _47+” hard gneiss and schist
Soil Profile Oi_ 0-1” hardwood leaves and twigs _A_1”-6” 10YR 3/4 sandy loam granular _E_6”-13” 10YR 6/3 sandy loam granular _Bt 13”-25” 2.5YR 4/6 clay blocky _BC 25”-35” 5YR 5/6 clay loam blocky _C_35”-47” saprolite massive _R_47+” hard gneiss and schist
___--0 to 8 inches; reddish brown (5YR 4/4) loam; moderate medium granular structure; friable; many fine roots; common fine pores; common fine black concretions; slightly acid, abrupt smooth boundary. (2 to 11 inches thick) ___--8 to 17 inches; yellowish red (5YR 4/6) clay; moderate medium subangular blocky structure; firm, sticky, plastic; common fine roots; few fine pores; many fine black concretions; common distinct clay films on faces of peds; slightly acid; gradual wavy boundary. ___--17 to 25 inches; yellowish red (5YR 4/8) clay; common fine distinct brownish yellow (10YR 6/6) mottles; moderate medium subangular blocky structure; firm, sticky, plastic; few fine roots; few fine pores; common black concretions; common distinct clay films on faces of peds; slightly acid; gradual wavy boundary. (Combined thickness of the Bt horizon is 12 to 35 inches.) ___--25 to 36 inches; yellowish red (5YR 4/8) clay loam; common medium faint reddish yellow (7.5YR 6/6) and common fine distinct yellowish brown (10YR 5/4) mottles; weak subangular blocky structure; firm, sticky, plastic; few fine black concretions; common fine lenses of gray clayey saprolite; slightly acid; gradual wavy boundary. (3 to 15 inches thick) ___--36 to 60 inches; mottled yellowish red (5YR 4/8), reddish yellow (7.5YR 6/6) and yellowish brown (10YR 5/4) highly weathered saprolite that has a sandy clay loam texture; massive; friable; many black and gray minerals; slightly acid
___--0 to 8 inches; reddish brown (5YR 4/4) loam; moderate medium granular structure; friable; many fine roots; common fine pores; common fine black concretions; slightly acid, abrupt smooth boundary. (2 to 11 inches thick) ___--8 to 17 inches; yellowish red (5YR 4/6) clay; moderate medium subangular blocky structure; firm, sticky, plastic; common fine roots; few fine pores; many fine black concretions; common distinct clay films on faces of peds; slightly acid; gradual wavy boundary. ___--17 to 25 inches; yellowish red (5YR 4/8) clay; common fine distinct brownish yellow (10YR 6/6) mottles; moderate medium subangular blocky structure; firm, sticky, plastic; few fine roots; few fine pores; common black concretions; common distinct clay films on faces of peds; slightly acid; gradual wavy boundary. (Combined thickness of the Bt horizon is 12 to 35 inches.) ___--25 to 36 inches; yellowish red (5YR 4/8) clay loam; common medium faint reddish yellow (7.5YR 6/6) and common fine distinct yellowish brown (10YR 5/4) mottles; weak subangular blocky structure; firm, sticky, plastic; few fine black concretions; common fine lenses of gray clayey saprolite; slightly acid; gradual wavy boundary. (3 to 15 inches thick) ___--36 to 60 inches; mottled yellowish red (5YR 4/8), reddish yellow (7.5YR 6/6) and yellowish brown (10YR 5/4) highly weathered saprolite that has a sandy clay loam texture; massive; friable; many black and gray minerals; slightly acid
Ap--0 to 8 inches; reddish brown (5YR 4/4) loam; moderate medium granular structure; friable; many fine roots; common fine pores; common fine black concretions; slightly acid, abrupt smooth boundary. (2 to 11 inches thick) Bt1--8 to 17 inches; yellowish red (5YR 4/6) clay; moderate medium subangular blocky structure; firm, sticky, plastic; common fine roots; few fine pores; many fine black concretions; common distinct clay films on faces of peds; slightly acid; gradual wavy boundary. Bt2--17 to 25 inches; yellowish red (5YR 4/8) clay; common fine distinct brownish yellow (10YR 6/6) mottles; moderate medium subangular blocky structure; firm, sticky, plastic; few fine roots; few fine pores; common black concretions; common distinct clay films on faces of peds; slightly acid; gradual wavy boundary. (Combined thickness of the Bt horizon is 12 to 35 inches.) BC--25 to 36 inches; yellowish red (5YR 4/8) clay loam; common medium faint reddish yellow (7.5YR 6/6) and common fine distinct yellowish brown (10YR 5/4) mottles; weak subangular blocky structure; firm, sticky, plastic; few fine black concretions; common fine lenses of gray clayey saprolite; slightly acid; gradual wavy boundary. (3 to 15 inches thick) C--36 to 60 inches; mottled yellowish red (5YR 4/8), reddish yellow (7.5YR 6/6) and yellowish brown (10YR 5/4) highly weathered saprolite that has a sandy clay loam texture; massive; friable; many black and gray minerals; slightly acid