Soil Horizons cont. Oa- highly decomposed Oi-undecomposed

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1 Soils Soil Basics

2 Soil Horizons

3 Soil Horizons cont. O Horizon: Or organic layer Organic layer of decomposing plant and animal tissue. Wooded upland areas have thin O horizons Wetlands may have thick O horizons Oa- highly decomposed Oi-undecomposed

4 Soil Horizons cont. A Horizon: topsoil Mineral layer that contains many organics (making it darker in color) Biologically active (roots, worms mammals etc.) Most effected by acid rain

5 Soil Horizons cont. Ap Horizon: plow or disturbed layer A mixed with O E: Elluvial Horizon Zone of leaching Light in color

6 Soil Pit!

7 Soil Horizons cont. B Horizon: subsoil Yellowish-reddish brown Accumulation zone (illuviation: movement into the horizon) Iron-oxide is a dominant mineral Gives B horizon its color

8 Soil Horizon Cont. C Horizon: Substratum Un-weathered geologic material the soil formed in. Glacial Till Outwash Lacustrine Shows little to no sign of soil formation. R Horizon: bedrock

9 Soil Color Used to distinguish and identify soil horizons, and group soils according to the soil clasification system called Soil Taxonomy. Easily identified property Used to related chemical/physical properties such as watertable, drainage, formation, and horizons.

10 Munsell soil color book

11 Soil Color cont. Organic matter: gives soil dark or black color Iron Oxides: Gives red/yellow/brown colors Iron, Sulfur, Manganese Gleyed Soils: are grey in color due to wetness. Redoximorphic Features (RMF s) Occur in wet (hydric) soils Fe is reduced wet conditions In dry times, the Fe may oxidize to create red/brown mottles Dark colors, grey colors, or splotchy (mottled) colors wet soils features are important for determining the depth of the water table Young vs. old soils Profile/structure development

12 Redoximorphic features

13 5 Soil Forming Factors Climate Precipitation, temperature, humidity Direct effects Temp. and precipitation weathering Indirect effects Vegetation

14 How the 5 factors influence soil formation

15 5 Soil Forming Factors Living Organisms Vegetation is most important Depends on climate, parent material, topography, drainage, etc. Microorganisms- decompose OM to provide nutrients

16 5 Soil Forming Factors Parent Material Till: mixed (unstratified) particle sizes laid down below ice Outwash: statified sands and gravel carried by glacial water; flat areas Loess: wind-blown silt-sized materials deposited over till and outwash Peat and Muck: organic, poorly drained soils

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18 5 Soil Forming Factors Topography Shape of land s surface Affects the distribution of parent material and vegetation. Soils on steep slopes are thinner Slope and aspect Water movement across landscape is the most important influence

19 5 Soil Forming Factors Time Mature Soils have maximum horizonation and are stable

20 3 Major Particles of Soil Sand- Coarse Sand: mm Very Fine Sand: mm Silt: mm Clay: <0.002 mm

21 Texture Sand- will not hold a ball in hand Loamy sand- will hold a ball in hand, wont ribbon Sandy loam- ribbons, gritty texture Silt loam- ribbons well, smooth, floury when dry Fine sandy loam- ribbons, less slippery in hand than silt loam Gravel- >2 mm *sand particles can be seen with eye while silt cannot.

22 Texture cont. Influences infiltration, percolation, water holding capacity, vegetation, and buildabilty Gives clues as to which parent material it is Silty-loess Sorted sands/gravels- outwash Boulders to silt- till

23 Soil Structure Grouping of soil particles into peds Structure forms when clay, OM, and iron oxides bind soil particles (See hand out for more details)

24 Consistence Resistance of peds to damage Loose (sand) Friable (good for farming) Firm (needs two hands to break) (See handout for more info)

25 Soil and Water Drainage: how fast excess water is removed based on slope, texture and vegetation Runoff: how much surface water flows over surface Primarily based on slope Permeability: infiltration rate How fast water flows through Depends on texture, structure, density and compaction

26 Soil Drainage classes Excessively drained-coarse Somewhat excessively drainedsandy Well drained- finer, drain readily Poorly drained- often wet to surface Very poorly drained- wet to surface with a thick organic layer

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28 AWC- Available Water Capacity The amount of water in soil that is available to plants AWC=FC-WP Field Capacity: water held in soil against gravity (after it drains)= most amount of water possible Wilting Point: Water held tightly in soil so plants cant use it= least amount of water possible Sandy soils: low AWC Clay soils: medium AWC Silty soils: Highest AWC ***Which is best for farming????

29 Soil Reaction/ CEC ph: 0-14, 7 neutral (water) ph is often increased for agriculture by liming Cation Exchange Capacity (CEC) Buffer capacity-ability to hold nutrients for plants Clays and OM have highest CEC

30 Vocab to Know! Perched water table Alluvium Drumlin Terraces Kames Eskers Mottling Gleyed Soil profile Soil Fragipan Illuvaition Stratified Solum Glacial outwash Outwash deposit/plains Drift AWC Glaciofluvial Iron oxide Glacial Till Moraine 5 Soil Forming Factors Structure Consistence Drainage Permeability Eluviation ANYTHING else in powerpoint Flash cards provided w/definitions

31 HA!