MLRA Soil Survey Leader Basic Soils Training Soil Morphology Nathan Jones MLRA Soil Survey Leader Andy Oxford Soil Scientist January 2013

Objectives Soil Horizons Soil Color Soil Texture Soil Structure Soil Rupture Resistance Soil Roots and Pores Soil Restrictive Layers Soil Boundaries Soil pH

SOIL MORPHOLOGY - a definition Characteristics and properties of the soil observable in the field within the various soil horizons The description of the kind and arrangement of soil horizons

Soil Horizons Ap Bt Bk Hetland Soil C We cannot describe or determine the properties of a horizon without first understanding what a soil horizon is. Hetland Soil C

Soil Horizons “Horizon”: A layer of soil or soil material approximately parallel to the land surface and differing from adjacent related layers in physical, chemical, and biological properties or characteristics such as color, structure, texture, consistence, or pH “Profile”: sequence of horizons stacked vertically that tells the story of how the soil formed “Series”: name given to profile that has characteristic set of properties and horizons (determined by NRCS)

Soil Sampling Units Houdek Series Purpose of this slide is to show how a pedon and its horizons can represent the landscape. Additionally, how the defined sequence of horizons with given properties represents a soil series. Finally, how both the soil series and landscape are used to create a map unit and ultimately a soil map. A soil map shows the location of a soil series on the landscape. Houdek Series

Soil Horizon Development A-Horizon development Accumulation of organic matter Clumping of individual soil particles Distinct from parent material and other layers B and C horizon development Carbonic and organic acids are carried by water into soil where they dissolve various minerals (transformations) Clay films - thin layers of oriented trans-located clay Salts and carbonates are carried by water and precipitate in the soil from upper to lower horizons (translocation) Wetting and drying cracks soils and creates soil structure Weathering of parent material

Master Horizons O = The layer of organic matter on the surface of a mineral soil A = Topsoil. The mineral soil horizon on the surface with organic matter and low clay E = The horizon of maximum leaching. Not in all soils, but if present, is located just below the “A” horizon B = Subsoil. Horizon most often located below A horizon. The zone of maximum clay accumulation C = Weathered rock. Lies below the “A” and/or “B” horizons and has NOT been acted upon by the soil forming processes R = The hard, consolidated rock beneath the soil Definition of Master horizons A horizon – usually has the highest organic matter and fertility. E horizon – if present, has a whitish color when dry, if wetted, whitish color disappear. Typically in concave landforms e.g. potholes B horizon – C horizon – R horizon -

O: litter, forest floor; Oi common, ½-1" thick; Oa,Oe usually very thin or absent   A: topmost mineral soil; 2-12" typical; use “p” if abrupt boundary (tillage mark) E: often absent due to erosion; may be light-colored, usually same texture as A; not blocky Transition: usually only one– BE or EB; B often first, since more distinct B: usually clayey, blocky, Fe coloration; 6-36" thick; may be subdivided (B1,B2); use t, w, or h– only one type per profile Transition: usually BC (B more distinct) C: weathered parent material; lower clay, massive/rock structure; if clear rock-like structure and appreciable rock fragments, use r (“Cr”) R: hard rock (cannot be dug); describe type if possible Skip the illustration. Maybe mention it is just another representation of the master horizons and includes other terms used to describe those layers, but do not discuss any of those terms. Main purpose is to show there are other letters (suffixes) used to describe horizons. Maybe mention a few of them, but do not discuss what they mean. Other purpose is to show there can be transitional horizons, generally between B and C horizons and E and B horizons.

Houdek soil series (SD State Soil) Bt Bk Group exercise #1: Allow volunteers from audience to separate and designate the horizons. Bring in Horizons one at a time. C

Soil Horizon Designations Tonka Soil A E Group exercise #2: Allow volunteers from audience to separate and designate the horizons. Bring in Horizons one at a time. B C

Barnes Soil A B Bk Group exercise #3: Allow volunteers from audience to separate and designate the horizons. All horizons come in at one time. C

Soil Properties Physical: particle size/arrangement; porosity Chemical: effect on plant growth Biological: determine long-term behavior (“sustainability”) Transition to soil properties observable within the soil horizons by showing and explaining the different categories of soil properties. Soil properties make up the bulk of soil morphology.

Physical Soil Properties Color Texture Structure Consistency Roots and Pores Restrictive Layers Another transition slide listing the physical soil properties that will be discussed in this training.

Soil Color McIntosh Soil

Soil Color Probably the most obvious soil feature Munsell system color charts used to standardize colors Hue = the dominant spectral color (related to wavelength of light) Value = measure of degree of lightness or darkness (amount of light reflected)

More Soil Color Chroma = measure of purity or strength of spectral color Dominant (matrix) color = the color that occupies the greatest volume Mottling refers to repetitive color changes that cannot be associated to a soil property. Redoximorphic (redox) features are a type of mottling associated with wetness

Soil Color: Pigments in Soils Dark brown to black: humus/organic matter gives soil this color; topsoils (A horizon) Reds and yellows: iron oxide, subsoil horizons (B horizons) either red, yellow, oxidized (Fe+3) iron well-oxidized (well-drained) Grey: reduced (Fe+2) iron; water doesn't drain out, poor drainage; Fe is reduced, depleted Whitish or light grey: leached out horizons; other pigments (humus, iron oxides) have been leached away  Munsell system: soil colors matched to color chips in book– standardized way to describe soil color

Munsell color chart: “10YR 5/3” hue value chroma

Soil Color Dark brown to black- Waubay Soil 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. Examples of the soil pigments described earlier.

Soil Color Reds and Yellows- Alabama State Soil Reds and Yellows- (B horizons) iron oxide formed during weathering, Fe+3 is well oxidized (well-drained) Examples of the soil pigments described earlier.

Soil Color Grey colors are caused by reduced Iron (Fe+2 ) Tonka Soil 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) Examples of the soil pigments described earlier.

Redoximorphic Features Redoximorphic (oxidation/reduction) Features Indication that soil is saturated for some time during the year Redox depletions (reduction) low chroma Fe and Mn have been stripped from soil Redox concentrations (oxidation) high chroma Accumulation of Fe and Mn oxides Point out the depletions and oxidations on the photo.

Soil Morphology Exercise 1 Color soil samples with a Munsell color book

Soil Texture

Soil Texture Definition (USDA ) - the weight proportion of the soil separates less than 2.0 mm in size (sand, silt, and clay). Or, more commonly, the relative proportions of sand, silt, and clay Sand = 2.0 to 0.05mm Silt = 0.05 to 0.002mm Clay = < 0.002mm Sand, silt, and clay in various proportions make up 12 textural classes

If you have it, bring out the basketball, tennis ball, and needle to illustrate the relative sizes of sand, silt, and clay.

USDA Textural Triangle

USDA Textural Triangle Example 35 % sand 55 % silt 10 % clay Texture is ‘silt loam’ Sand 0.05 - 2.0 mm Silt 0.002 to .05 mm Clay < .002 mm Textural Class The percentage of sand sized particles + % of silt sized particles + % of clay sized particles Example of how to use the Textural Triangle. Provide another example and have the audience determine the texture.

Coarse Fragments Mineral particles larger than 2.0 mm = rock fragments (gravels, stones, or boulders) Modifiers = 0 - 15%, 15 - 35%, 35 - 60%, 60-90%, > 90% Soil texture refers to the sizes of the mineral soil particles and is modified as well as the amount and type of organic matter in a soil horizon. Soil texture is made up of a “textural class” and any “modifier” that is appropriate. The total of the mineral soil particles less than 2 mm are collectively referred to as the “fine earth fraction”. This fine earth fraction is what we use to determine the textural class. The mineral soil particles greater than 2 mm are referred to as coarse fragments. These are used to give the textural class a modifier. Can anyone give me an example of a soil textural class? If that 15 % or more of that SiL were gravels, the textural class would get a modifier of “gravely sil”.

Coarse Fragments Gravels: 2.0 to 75 mm Cobbles: 76 to 250 mm

Coarse Fragments Stoney: 250 to 600mm Boulders: 600mm+

TEXTURAL CLASSES BY “FEEL” METHOD Texture by feel method chart.

Soil Morphology Exercise 2 Texture by “feel” method

Soil Structure

Soil Structure - a definition The aggregation of primary particles into secondary units surrounded by planes of weakness. Granular Blocky Platy Prismatic Columnar Massive wetting and drying freezing and thawing root action animal activity organic matter kind of clay Initial material Ped face Pores Porosity 30 to 60 % of ped volume If soil texture is the plywood, 2 X 6 ‘s, and nails that can be packed on a truck, soil structure is the building put together using the plywood, 2 X 6 ‘s, and nails. Structure creates porosity and surfaces for chemical and physical process

Soil Structure - Shapes Granular - peds are approximately spherical or polyhedral and are bounded by curved or irregular faces (A horizons) Platy - the peds are flat and “platelike”; they are usually oriented horizontally (E horizons) Blocky - somewhat “blocklike”; bounded by flat or slightly rounded surfaces; nearly equidimensional (Upper B horizons) Prismatic - peds are longer than they are wide (Lower B horizons) Massive – no structural units; material is a coherent mass (C horizons) Single grain – no structural units; entirely noncoherent; example is loose sand (C horizons)

Soil Structure - Shapes Granular - peds are approximately spherical or polyhedral and are bounded by curved or irregular faces (A horizons) Platy - the peds are flat and “platelike”; They are usually oriented horizontally (E horizons)

Soil Structure - Shapes Blocky - Somewhat “block like”. Bounded by flat or slightly rounded surfaces; Nearly equidimensional (Upper B horizons) Angular Blocky Subangular blocky Prismatic - Peds are longer than they are wide (Lower B horizons)

Soil Structure - Shapes Columnar – Similar to prismatic; vertically elongated units with rounded tops; found in natric horizons

Soil Structure Affects: Pore space Liquid and gas movement Permeability Structure is strongly correlated to many properties, particularly soil hydrology

Soil Morphology Exercise 3 Observe structure types using the structure kits

Soil Rupture Resistance

Soil Rupture Resistance - a definition The resistance of soil to deformation or rupture; or the degree of cohesion (tendency of similar surfaces to cling to one another) or adhesion (tendency of dissimilar surfaces to cling to one another) of the soil mass

Soil Rupture Resistance - Moist Soil loose very friable friable firm very firm extremely firm

Soil Rupture Resistance Loose: You have trouble picking out a single ped and the structure falls apart before you handle it.* Friable: The ped breaks with a small amount of pressure. Very Friable * Soils with “single grained” structure always have loose consistence. Firm: The ped breaks when you apply a good amount of pressure and dents your fingers before it breaks. Extremely Firm: The ped can’t be crushed with your fingers (you need a hammer!). Very Firm

Soil Morphology Exercise 4 Practice determining moist rupture resistance class

Soil Roots and Pores

Soil Roots and Pores Describe the quantity, size, and location of roots and pores Provides a visual representation of soil health Affected by soil structure Impacted by soil restrictive layers and management and use

Soil Roots and Pores

Soil Restrictive Layers Soil material Shale bedrock

Soil and Root Restrictive Layers Bedrock Natric horizons Sand and gravel Clay pan Water Compaction

Soil Restrictive Layers Influences: Rooting depth Water infiltration Salt accumulation Land use and management

Soil Boundaries

Soil Boundaries - a definition A surface or transitional layer between two adjoining horizons or layers Most boundaries are zones of transition rather than sharp lines of division

Soil Boundaries - Distinctness Abrupt = less than 1 inch thick Clear = 1 to 2.5 inches thick Gradual = 2.5 to 5 inches thick Diffuse = greater than 5 inches thick

Soil Boundaries - Topography Smooth = the boundary is a plane with few or no irregularities Wavy = there are undulations in which depressions are wider than they are deep Irregular = pockets that are deeper than they are wide Broken = One or both of the horizons separated by the boundary are discontinuous and the boundary is interrupted

Soil Boundaries Describe the boundaries in these pictures.

Soil Chemical Properties Acidity/alkalinity: “pH” Affects many other soil chemical properties Large effect on nutrient availability (solubility) Optimum range (most plants): 5.5-6.5

Soil pH

Soil pH – definition A numeric designation of the acidity or alkalinity in soils A measure of the H+ ion activity in soils On a scale of 0 to 14

Soil pH - classes Very strongly acid: 4.5 to 5.0 Moderately Acid: 5.6 to 6.0 Slightly Acid: 6.1 to 6.5 Neutral: 6.6 to 7.3 Slightly Alkaline: 7.4 to 7.8 Moderately Alkaline: 7.9 to 8.4

Soil pH pH influences nutrient availability, rate of biological and chemical processes, the amount and types of plants and microorganisms present, and the corrosion potential of concrete or steel structures in the soil You can alter the soil pH by incorporating compounds in to the soil. The most common is to add lime (calcium carbonate, CaCO3 ) to increase the pH

Soil pH-nutrient availability

Questions??

Credits Pictures and Content from PowerPoint Presentations Created by: William Miller and David Radcliffe, Crop and Soil Sciences, University of Georgia University of Florida Soil Lab Alabama A&M University USDA Natural Resources Conservation Service Alaska Soil Survey Program Earl D. Lockridge, USDA NRCS National Soil Survey Center

Credits Other pictures and content provided by: USDA Handbook No. 18, Soil Survey Manual by the Soil Survey Division Staff Field Book for Describing and Sampling Soils Version 2.0 by USDA NRCS National Soil Survey Center USDA NRCS Keys to Soil Taxonomy 10th Edition Verdegaalbrothers.com Stthomas.edu Soilquality.org Noonturfcare.com Viette.com Ehow.com Gardeningstepbystep.com Mccc.msu.edu Deeproot.com Swac.umn.edu Scifaithkansas.net Allianceforwaterefficiency.org Ecoclublive.blogspot.com Sd.nrcs.usda.gov Water-research.net